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Electronics => Beginners => Topic started by: electroniclearner820327 on July 13, 2025, 09:37:24 am
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I just had the idea to get one of these due to not trusting the intermittent battery light so then I can monitor the actual voltage when driving without having to pop the hood at a layby and check manually when that light is coming on and off.
I have been monitoring it more regularly now after driving and so far have not seen any decline in voltage when I park up so doesn't seem to be an indicator of battery drainage.
Having something like this (https://www.demon-tweeks.com/uk/simoni-racing-digital-voltmeter-sravolt-1/) I feel would give peace of mind as regardless, of the light not having correlated with actual battery malfunction yet, it does make me twitchy each time it decides to come on while driving.
With a dedicated voltmeter for it I could feel more confident.
How would I wire it? As I already have a connection running from the vehicle battery into the back to the dc-dc charger anyway, could I piggyback on those wires somewhere to save me having to run another long length out to the motor? I am guess yes? If so where and how should it be put on? Of course in the right place on the run, but how in terms of wiring technicalities? I could put the positive for the device into the positive on the terminal of the battery isolator switch between the starter positive to dc-dc charger positive input then negative can go to the negative busbar for the everything else, including the circuit for the starter and leisure as the instructions for the dc-dc charger stipulated they should share a common negative so I ran that cable into the back as well?
Btw could the light coming on be an indication of the voltage being too high rather than too low? I did read in the manual and it did not indicate that as a reason it would come on from what I recall.
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The voltmeter draws only a small amount of current, so you can basically connect it anywhere that you can find 12V, provided that the 12V disappears when the ignition is switched off. That means you shouldn't connect it directly to the battery. However, your vehicle probably has a 12V socket (used to be for the cigarette lighter), and provided that goes dead when the ignition is switched off, that could be an ideal solution.
In your fifth paragraph you discuss various places you could connect the voltmeter, but without knowing a lot more detail about the exact wiring it's hard to advise you on this. Because of the low current drawn by the voltmeter, you can safely connect it to any negative busbar or other negative feed. It's the 12V feed that must go on and off with the ignition switch.
In the old days the battery light was connected directly to the alternator and showed whether the alternator was energised and producing current (it went off when the alternator was producing enough voltage to keep itself energised). Nowadays I don't know if that is still true. It could be that the battery light is switched on and off by an ECU (electronic control unit), in which case it could be ised to indicate an excessively high voltage as well as a failure to charge. It is certainly possible, but I'm afraid I don't know whether it is actually done.
But your voltmeter will let you see what is happening. You should expect to see a voltage of at least 14.0V when the battery is charging.
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You might try connecting it to the cigarette lighter socket -- the socket is usually turned off when the car isn't running.
There may be some regulation between the battery and the socket -- that's something to test.
There are a lot of such voltmeters available online at the usual places -- Amazon, ebay, Aliexpress.
https://search.brave.com/images?q=cigarette%20lighter%20volt%20meter
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Good Morning Electroniclearner820327, I've got one of these that works by Bluetooth to your cellphone:
https://www.amazon.com/QUICKLYNKS-Battery-Monitor-Bluetooth-Device/dp/B01MT4583U/ref=sr_1_7?adgrpid=1334807686682980&dib=eyJ2IjoiMSJ9.QdLsGesFXqoRom3VDNiZvsUrnYdHFcFlKeRwZYOFudQ7tl9P8yDSMmhfZ_zn3dczRB8qnZxn7bH8QPxlHIiM8xYfPes62eQZo23T9eq7iiuBhJ_cY_VNan3phgkrQpS0xg-uT19sUNADUs5fQs3uNTlImZBf2UvKJ2SlU_PVlVj-n9EYhU3xq8ofywbQNb9Ni8JlHlPmJQYX4TrUAYLPjgi4MowchXUaNuZiNSmnwJN8nehAwlZIA3xM6G4h2Ei_BYzZQgdU1T_jLDbudapawpHboO1TjxlTZ-wQ8s5QFR0.DhK6BQHtS_-z8Htg_rS0_3bhSTM3uoRBwBCXATPsO4k&dib_tag=se&hvadid=83425629455349&hvbmt=be&hvdev=c&hvlocphy=59456&hvnetw=o&hvqmt=e&hvtargid=kwd-83425837482286%3Aloc-190&hydadcr=24629_13493443&keywords=bluetooth%2Bbattery%2Bmonitor&mcid=4f80857b083939acb3732e45655aa81d&msclkid=995e1c7c41781f010073740fe8f7d906&qid=1752410521&sr=8-7&th=1 (https://www.amazon.com/QUICKLYNKS-Battery-Monitor-Bluetooth-Device/dp/B01MT4583U/ref=sr_1_7?adgrpid=1334807686682980&dib=eyJ2IjoiMSJ9.QdLsGesFXqoRom3VDNiZvsUrnYdHFcFlKeRwZYOFudQ7tl9P8yDSMmhfZ_zn3dczRB8qnZxn7bH8QPxlHIiM8xYfPes62eQZo23T9eq7iiuBhJ_cY_VNan3phgkrQpS0xg-uT19sUNADUs5fQs3uNTlImZBf2UvKJ2SlU_PVlVj-n9EYhU3xq8ofywbQNb9Ni8JlHlPmJQYX4TrUAYLPjgi4MowchXUaNuZiNSmnwJN8nehAwlZIA3xM6G4h2Ei_BYzZQgdU1T_jLDbudapawpHboO1TjxlTZ-wQ8s5QFR0.DhK6BQHtS_-z8Htg_rS0_3bhSTM3uoRBwBCXATPsO4k&dib_tag=se&hvadid=83425629455349&hvbmt=be&hvdev=c&hvlocphy=59456&hvnetw=o&hvqmt=e&hvtargid=kwd-83425837482286%3Aloc-190&hydadcr=24629_13493443&keywords=bluetooth%2Bbattery%2Bmonitor&mcid=4f80857b083939acb3732e45655aa81d&msclkid=995e1c7c41781f010073740fe8f7d906&qid=1752410521&sr=8-7&th=1) :popcorn:
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For accuracy, ideally a battery voltmeter should be wired direct to the battery terminals, so you are measuring the actual battery voltage, not the battery voltage minus whatever voltage drops exist in the vehicle wiring harness. The positive wire to the voltmeter should be fused with a 1A inline fuse as close as reasonably possible to the battery terminal.
The voltmeter itself may have separate connections for instrument power and measured voltage, (very common with LED display digital types that have relatively high power consumption), and in that case the measured voltage connection should come from the battery and the instrument power from a (fused) switched accessory positive from the ignition switch. Its also common for cheap LED voltmeters to either have a single negative connection or to have two, that pretend to be separate but actually have direct connection on the PCB between them. In that case, do *NOT* connect the power negative to chassis or a ground from the wiring loom, it needs to go direct back to the battery, again to avoid measuring wiring loom voltage drops.
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For accuracy, ideally a battery voltmeter should be wired direct to the battery terminals, so you are measuring the actual battery voltage, not the battery voltage minus whatever voltage drops exist in the vehicle wiring harness.
I knew someone would bring this up, but I think it only complicates things. He just needs some idea of if and when the battery is being charged. That's why I suggested the cigarette lighter socket. It will be more than sufficient to do the job.
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Well if your accuracy requirements are low enough, you can get complete voltmeters that plug in the lighter socket, e.g. this one: https://www.amazon.co.uk/Multibao-Cigarette-Voltmeter-Voltage-Detector/dp/B09NPMP8CB (https://www.amazon.co.uk/Multibao-Cigarette-Voltmeter-Voltage-Detector/dp/B09NPMP8CB)
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I just get a cheap battery powered DMM and the lghier plug. No mod and after a while if there is no problem you don't need it. With a 10 Megahohms input impdedance whatever resistance in the wiring harness is insignificant.
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While connecting a voltmeter to a convenient 12V source like the cigarette lighter might give a general indication of charging, Ian.M is absolutely right - if your goal is to monitor the actual battery voltage accurately, especially under load or fault conditions, the meter must be wired directly to the battery terminals.
This is because voltage drops across vehicle wiring - caused by current draw from other components, wire resistance, poor connections, or corrosion can significantly distort the reading. For example, if there's a heavy load on the same wire, you'll see an artificially low voltage, if there's current flowing into the wire (e.g. from a charger, solar panel, etc), the reading might be falsely high. These effects depend on unpredictable random factors like wire condition and contact quality.
For reliable results, especially when diagnosing intermittent issues like warning lights, only direct battery terminal measurements with proper inline fuse protection can ensure you're seeing what the battery itself "sees."
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A 50 µA panel instrument, a TL431 as adjustable zener and a new scale. Draws less than the self discharge current of a 50-100 Ah car battery. (Separate 100 Ah battery used with solar panels on roof rack for photo safaris in my case.)
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While connecting a voltmeter to a convenient 12V source like the cigarette lighter might give a general indication of charging, Ian.M is absolutely right - if your goal is to monitor the actual battery voltage accurately, especially under load or fault conditions, the meter must be wired directly to the battery terminals.
This is because voltage drops across vehicle wiring - caused by current draw from other components, wire resistance, poor connections, or corrosion can significantly distort the reading. For example, if there's a heavy load on the same wire, you'll see an artificially low voltage, if there's current flowing into the wire (e.g. from a charger, solar panel, etc), the reading might be falsely high. These effects depend on unpredictable random factors like wire condition and contact quality.
For reliable results, especially when diagnosing intermittent issues like warning lights, only direct battery terminal measurements with proper inline fuse protection can ensure you're seeing what the battery itself "sees."
Huh?
If there would be a voltage drop it would mean there is an issue.
The idea is to know whether the battery is being charged or not.
You do t need a 6.5 digit meter for that nor any exact battery voltage as any 12V power line will tell you if there is a problem or not.
But even a voltmeter will not tell you if there is enough charge in the battery.
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Selected one of the many digital voltmeters available online, trimmed the lead wire to proper length, attached a cigarette-lighter plug, double sticky tape, and in less than 15 minutes you are good to go.
This particular model will display two decimals below 10.0 volts, but even a single decimal is enough for general purpose battery monitoring.
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The idea is to know whether the battery is being charged or not.
You do t need a 6.5 digit meter for that nor any exact battery voltage as any 12V power line will tell you if there is a problem or not.
You're right that any significant voltage drop typically indicates a problem - but only if you're measuring at the correct point. That’s exactly why connecting a voltmeter anywhere other than directly at the battery terminals can be misleading.
In a vehicle, wires and connections are exposed to vibration, moisture, corrosion, and mechanical wear. A wire might be partially damaged, corroded, or have a poor contact, which can create resistance. As a result, the voltage at some 12V line inside the vehicle might appear low - making it seem like the battery is undercharged - even if the battery is actually in perfect condition. Or worse, it might appear normal while the battery is failing, simply because you're measuring after a faulty connection.
If your goal is to know whether the battery itself is being charged, and what its voltage is under various conditions, then the only reliable method is to measure voltage at the battery terminals. This eliminates the influence of unknown or degrading vehicle wiring and ensures you're seeing the true battery status - not what’s happening downstream at, say, the cigarette lighter or a fuse panel.
In short: if you want to monitor the battery, measure at the battery. Anything else may tell you more about the wiring than the battery itself.
But even a voltmeter will not tell you if there is enough charge in the battery.
a voltmeter alone won’t give you the full picture of battery health unless it's connected directly to the battery terminals and used properly.
When voltage is measured at the battery terminals, you can absolutely assess both the state of charge and get a good indication of the battery’s condition. Measurements taken elsewhere in the vehicle’s wiring, such as at a cigarette lighter or accessory circuit - are affected by wire resistance, voltage drops, and potential faults. These measurements not only fail to represent the actual battery voltage but can’t reliably indicate battery condition at all.
To evaluate state of charge, just let the battery rest for 30-40 hours at ~25°C without any load or charging. Then measure the open-circuit voltage directly at the battery terminals. This gives you the battery’s EMF. Then you can estimate the charge level in percents with this simple approximation:
State of charge (%) = (Voltage - 11.7) * 100
To assess internal resistance, again connect the voltmeter directly to the terminals. Measure the voltage with no load, then under a significant load (e.g., headlights + heater).
Even without measuring current, a large voltage drop under load indicates high internal resistance - a sign of battery aging or failure.
But notice very important thing - in all cases, reliable conclusions require voltage measurement directly at the battery terminals. Anything else may mislead you due to unknown wiring losses or faults.
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This particular model will display two decimals below 10.0 volts, but even a single decimal is enough for general purpose battery monitoring.
Your photo shows 12.0 V, which is quite low and potentially concerning. If the engine is off and there's no charging, this voltage indicates a low state of charge - roughly around 30%. A healthy, fully charged battery should read about 12.7 V at rest (no load, no charging).
After charging, the battery may retain higher voltage for some time (due to internal chemical processes), which gradually stabilizes to its true open-circuit voltage 12.7 V over the course of approximately 30-40 hours.
If the engine is running and charging is active, you should typically see 13.0 to 14.4 V, depending on the vehicle and temperature.
So while a single decimal reading is sufficient for general monitoring, a consistent reading of 12.0 V should be investigated further. in most cases, this discrepancy is due to the fact that you're measuring voltage somewhere within the vehicle’s wiring rather than directly at the battery terminals. Your example with a plug-in voltmeter in the cigarette lighter illustrates this well - it highlights the practical limitations and potential inaccuracy of such measurements.
For meaningful and reliable battery voltage readings, the voltmeter should be connected directly to the battery terminals. Only then you can accurately assess the battery’s actual condition and charging state.
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The idea is to know whether the battery is being charged or not.
You do t need a 6.5 digit meter for that nor any exact battery voltage as any 12V power line will tell you if there is a problem or not.
You're right that any significant voltage drop typically indicates a problem - but only if you're measuring at the correct point. That’s exactly why connecting a voltmeter anywhere other than directly at the battery terminals can be misleading.
In a vehicle, wires and connections are exposed to vibration, moisture, corrosion, and mechanical wear. A wire might be partially damaged, corroded, or have a poor contact, which can create resistance. As a result, the voltage at some 12V line inside the vehicle might appear low - making it seem like the battery is undercharged - even if the battery is actually in perfect condition. Or worse, it might appear normal while the battery is failing, simply because you're measuring after a faulty connection.
If your goal is to know whether the battery itself is being charged, and what its voltage is under various conditions, then the only reliable method is to measure voltage at the battery terminals. This eliminates the influence of unknown or degrading vehicle wiring and ensures you're seeing the true battery status - not what’s happening downstream at, say, the cigarette lighter or a fuse panel.
In short: if you want to monitor the battery, measure at the battery. Anything else may tell you more about the wiring than the battery itself.
But even a voltmeter will not tell you if there is enough charge in the battery.
a voltmeter alone won’t give you the full picture of battery health unless it's connected directly to the battery terminals and used properly.
When voltage is measured at the battery terminals, you can absolutely assess both the state of charge and get a good indication of the battery’s condition. Measurements taken elsewhere in the vehicle’s wiring, such as at a cigarette lighter or accessory circuit - are affected by wire resistance, voltage drops, and potential faults. These measurements not only fail to represent the actual battery voltage but can’t reliably indicate battery condition at all.
To evaluate state of charge, just let the battery rest for 30-40 hours at ~25°C without any load or charging. Then measure the open-circuit voltage directly at the battery terminals. This gives you the battery’s EMF. Then you can estimate the charge level in percents with this simple approximation:
State of charge (%) = (Voltage - 11.7) * 100
To assess internal resistance, again connect the voltmeter directly to the terminals. Measure the voltage with no load, then under a significant load (e.g., headlights + heater).
Even without measuring current, a large voltage drop under load indicates high internal resistance - a sign of battery aging or failure.
But notice very important thing - in all cases, reliable conclusions require voltage measurement directly at the battery terminals. Anything else may mislead you due to unknown wiring losses or faults.
Sorry but this is a kind of nonsense.
I have been analyzing car electronics and car battery issues for more than 20 years.
You can reliably measure the battery voltage at any point in the car.
Again (as I said before), if there would be an issue with the location of measurement because of what ever reason ( bad contact) then that is exactly what you would want to know, so definitely not measure straight at the battery itself.
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electroniclearner820327, intermittent battery light is on the vehicle's instrument cluster, but not sure what a "cab" means in the UK. What vehicle is this? Here a cab=taxicab. Some semi trucks (24V) have a cab though.
The alternator lamp can caused by many things, usually it's the brushes worn out, a belts, bad connection- that causes the alternator to intermittently cutout. Check the wiring - including the battery terminals. Very important.
A modern vehicle has ECU-control and there are many extra reasons for the light to come on. Overheating alternator (plugged vents), voltage too high or low, no output, battery voltage low, overcurrent etc.
For a few decades I have used a voltmeter in vehicles. Some at the cig lighter, others wired direct.
Not a huge difference, there is (at cig lighter) extra voltage drop due to the wiring and electrical loads but still good enough to check the charging voltage. You might see 0.2V of slop.
You can buy cheap voltmeters for a couple pounds from Aliexpress (https://www.aliexpress.com/w/wholesale-car-voltmeter.html?g=y&SearchText=car+voltmeter) or eBay etc.
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Sorry but this is a kind of nonsense.
I have been analyzing car electronics and car battery issues for more than 20 years.
You can reliably measure the battery voltage at any point in the car.
Again (as I said before), if there would be an issue with the location of measurement because of what ever reason ( bad contact) then that is exactly what you would want to know, so definitely not measure straight at the battery itself.
I’m genuinely unsure whether you're being trolling or serious. Are you truly suggesting "after 20 years of experience" that one can reliably assess battery condition by measuring voltage at any random point in the vehicle’s wiring? This is complete nonsense.
Sorry, but even a junior technician with basic electrical knowledge understands that according to Ohm’s law, any resistance in the wiring - due to length, connectors, corrosion, or poor contacts will cause voltage drops under load or charging. These drops make such measurements inherently unreliable for evaluating the true state of the battery.
I don't believe that a person "with 20 years of experience" with car wiring can not know Ohm's law.
If your goal is to assess the battery itself, not the condition of downstream wiring, the only correct method is to measure voltage directly at the battery terminals. Anything else reflects conditions in the wiring, not the battery.
Personally, I would never trust voltage readings taken from a cigarette lighter socket even if using a high-precision, calibrated instrument simply because I understand the inherent limitations of such a measurement point and why the results cannot be considered reliable.
That’s precisely why, whenever I need to verify the battery voltage, I open the hood, take a digital multimeter, and measure it directly at the battery terminals. While my car alarm system does provide onboard voltage monitoring - even with remote access - I don't rely on those readings, as I’ve repeatedly observed discrepancies compared to the actual voltage measured at the terminals.
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Sorry but this is a kind of nonsense.
I have been analyzing car electronics and car battery issues for more than 20 years.
You can reliably measure the battery voltage at any point in the car.
Again (as I said before), if there would be an issue with the location of measurement because of what ever reason ( bad contact) then that is exactly what you would want to know, so definitely not measure straight at the battery itself.
I’m genuinely unsure whether you're being trolling or serious. Are you truly suggesting "after 20 years of experience" that one can reliably assess battery condition by measuring voltage at any random point in the vehicle’s wiring? This is complete nonsense.
Sorry, but even a junior technician with basic electrical knowledge understands that according to Ohm’s law, any resistance in the wiring - due to length, connectors, corrosion, or poor contacts will cause voltage drops under load or charging. These drops make such measurements inherently unreliable for evaluating the true state of the battery.
I don't believe that a person "with 20 years of experience" with car wiring can not know Ohm's law.
If your goal is to assess the battery itself, not the condition of downstream wiring, the only correct method is to measure voltage directly at the battery terminals. Anything else reflects conditions in the wiring, not the battery.
Really?
Are you going to explain an engineer what Ohms law is?
It seems you don’t understand what TS is looking for.
Read between the lines.
And try to understand why I’m telling its better to measure somewhere down the road instead of next to the battery.
It seems I have to explain some basics too.
Anyway, other members here have explained well what TS could or should even should do.
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Old cars, power went through the ignition switch first and the loop de loop back to the alternator and under hood loads. There is a sizeable voltage drop due to this.
Modern cars, for power loads they use relays located under the hood. It's close to the alternator and battery.
You don't see big voltage drops at the cig lighter, other than close by local stuff like the cabin blower fan.
Headlights, cooling fan, air con, some ABS - the bigger loads takeoff points are under the hood.
My Toyota uses #20AWG wire for the cigarette lighter "accessory outlet" with 3A fuse, it's pretty cheap- minimum copper is the goal nowadays.
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Old cars, power went through the ignition switch first and the loop de loop back to the alternator and under hood loads. There is a sizeable voltage drop due to this.
Modern cars, for power loads they use relays located under the hood. It's close to the alternator and battery.
You don't see big voltage drops at the cig lighter, other than close by local stuff like the cabin blower fan.
Headlights, cooling fan, air con, some ABS - the bigger loads takeoff points are under the hood.
My Toyota uses #20AWG wire for the cigarette lighter "accessory outlet" with 3A fuse, it's pretty cheap- minimum copper is the goal nowadays.
It depends on what you consider an old car: even in the 80’s cars had a permanent 12V power supply ( so not going through the ignition switch) for the radio to keep its memory and other things.
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Modern cars, for power loads they use relays located under the hood. It's close to the alternator and battery.
You don't see big voltage drops at the cig lighter, other than close by local stuff like the cabin blower fan.
If other devices are connected to the cigarette lighter circuit such as a dashcam, phone charger, or similar accessories - voltage drops can and often do occur, especially under load or if the wire is partially shorting to ground - with high enough resistance to avoid triggering a fuse or being noticed as a full short circuit, but still low enough to significantly affect the voltmeter readings.
But the larger issue is that unless you personally installed and thoroughly verified the entire wiring path, you can’t be certain of its condition, what additional loads might be present, or exactly where in the power distribution the cigarette lighter is connected. That uncertainty makes any voltage readings taken from it unreliable for assessing actual battery voltage.
Even if you did wire everything yourself and are confident in the quality, automotive wiring is constantly exposed to vibration, temperature changes, and corrosion. Over time, this can degrade contacts and increase resistance - which again makes voltmeter readings from the cigarette lighter an unreliable diagnostic source.
PS: I once witnessed a situation involving a so-called "engineer" at an authorized Toyota service center who had modified the vehicle’s wiring. From his perspective, everything appeared to be done correctly. However, he failed to realize that the wire in question was carrying digital data, not just a simple control signal. As a result, the modification led to intermittent malfunctions of the power window control system.
He spent a long time troubleshooting the issue without understanding its cause. When I tried to get clarity on what was going on, he was defensive, insisting that he was a certified engineer and knew what he was doing, citing service procedures and internal regulations. Eventually, I managed to get enough information from him to understand the root of the problem - and it became clear almost immediately.
Needless to say, my opinion of his professionalism changed significantly, and I never went back to that service again. This is the real case that happens with me in the past. Since then, I have made it a point to thoroughly verify and oversee any work performed by so-called "engineers" at authorized service centers.
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I find it's about the wiring voltage drops, and at the take-off point too. It's not about what is supplied battery power. In the 1960's it was the clock that got battery power, 80's the radio, 90's the power door lock remote RX etc.
Radio BATT+ connects to where? The fusebox bus, along with a dozen other devices. If the fusebox is located under the hood, or in the cabin kickpanel it's a couple metres extra wire.
Point is, that node you will see the sag in voltage if many loads are running. Not due to the one radio BATT+ wire though.
Again it's not enough voltage to be really far off the state of the electrical system. As well, you have the ground voltage drops to look at and include.
Cigarette lighter usually grounded to the body/firewall which is a ways away from the battery and a lot of steel.
I will play with it, experiment - rear window defog, brake lights are popular (not under the hood, rear of vehicle) loads.
I just bought a car voltmeter 52mm Stepmaster (https://ketgauge.com/products/stepmaster-volts-gauge) (stepper motor analog pointer) and it works gross. Drove me nuts needle bobbing up and down, despite the 5-1/2 digital LED display one being pretty stable - at the cig lighter. Had to take the scope out to the car and look at the noise spikes. The ignition system and fuel pump are most of it.
edit: added pic, these are a chinese clone of the Japanese Defi gauge
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You're absolutely right - when measuring voltage at an arbitrary point in the vehicle wiring, such as the cigarette lighter, you're observing not just the battery voltage but the combined effects of voltage drops along the wiring path. Current may be flowing through shared sections of wire due to other active loads, and those wires may be long, undersized, or using the vehicle chassis as part of the return path.
Each of these elements - wire length, connections, shared circuits, grounding through body panels - introduces potential sources of voltage drop, or instability. If the voltmeter itself is powered from the same circuit it’s measuring (as many plug-in meters are), the readings can be further distorted under load.
This is precisely why accurate battery voltage measurements must be taken directly at the battery terminals. The difference becomes especially evident when testing battery internal resistance under load - for example, by switching on high-current consumers like headlights and heating elements. In such cases, the voltage drop at remote points (the cigarette lighter) can be significantly greater than at the terminals due to high current, misleading your assessment of battery condition.
Also, as you’ve already noticed, the quality of the voltmeter matters. Many low-cost plug-in car voltmeters lack proper filtering, temperature compensation or accuracy, and are easily affected by electrical noise from the ignition system, fuel pump, or other switching loads. For serious measurements, even an inexpensive but proper handheld DMM will generally offer better reliability and stability.
For that reason, whenever I need to accurately assess the battery’s state of charge or condition, I always use a multimeter connected directly to the battery terminals.
As I mentioned earlier, in my vehicle the battery voltage is monitored both by the onboard electronics and the security system, allowing me to remotely check the voltage via the security remote control unit. The displayed value is shown with one decimal place and often matches the actual battery voltage - but not consistently. Sometimes I see no difference with DMM on battery terminals, but sometimes I see 0.1..0.3V difference. It's difficult to say whether the discrepancies are due to voltage drops within the wiring or the limited accuracy of the security system's ADC, I just don’t spend much time analyzing it, as I recognize that this method of measurement is inherently unreliable.
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Even if you go through all the hoops - ECU-controlled alternator can confuse you. They don't keep a lead-acid battery at 100%, they'll do regen and charge if you are decelerating. To achieve a higher fuel economy number. It's terrible I have to manually top up the battery (charge to 14.4v) every month or two. Many cars also have a current-sensor at the battery terminal so the ECU knows what the load is.
I'll see 13.2V-13.4V which is normal for Toyota in summer. They use a lower voltage for some reason, I think it's less water loss. After starting it will go up to 14.0V for a while.
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yeah, charging voltage control in modern vehicles can be quite unpredictable. It's difficult to determine the exact logic behind the ECU choice of charging voltage. In my own experience, I typically observe values in the range of 13 to 14 volts, though occasionally it drops below 13 V or rises above 14 V, probably depending on driving conditions, temperature, and system behavior.
One thing I’ve noticed is that charging behavior also seems to depend on the type of battery installed. For example, with a conventional lead-acid battery, the system would regularly charge up to around 14.4 V. In contrast, with my current hybrid battery, the charging voltage tends to stay lower - typically around 13.5 to 14 V. It's difficult to say what exactly causes this difference, as I haven’t changed any settings - the system configuration remains the same.
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Pardon my intrusion here, as I am certainly not any kind of automotive expert.
However, it seems to be after reading this thread that the objections to using something like a voltmeter plugged into the cigarette lighter socket are kind of uncalled for.
This because of what seems to be the OP's motivation here:
I just had the idea to get one of these due to not trusting the intermittent battery light so then I can monitor the actual voltage when driving without having to pop the hood at a layby and check manually when that light is coming on and off.
I have been monitoring it more regularly now after driving and so far have not seen any decline in voltage when I park up so doesn't seem to be an indicator of battery drainage.
Having something like this I feel would give peace of mind as regardless, of the light not having correlated with actual battery malfunction yet, it does make me twitchy each time it decides to come on while driving.
Now, they didn't say what kind of accuracy they were aiming for; they'll have to tell us this themselves.
But it seems like they want something a little better than a "go/no go" indicator.
I don't think the voltage drop caused by whatever wiring there is betwixt battery and cig-lighter socket would be significant here. The relative voltage indications between a battery in a known-good state and otherwise should be sufficient for their purposes.
I'll let them (the OP) speak for themself to clear this up.
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I don't think the voltage drop caused by whatever wiring there is betwixt battery and cig-lighter socket would be significant here. The relative voltage indications between a battery in a known-good state and otherwise should be sufficient for their purposes.
the concern here lies in the precision required to meaningfully assess battery condition or charging voltage. Even a deviation as small as 0.2-0.5 V can lead to a completely incorrect interpretation. Typically you need < 0.1 V error for a good lead acid battery assessment.
For example, a resting voltage of 12.7 V typically indicates a fully charged and healthy lead-acid battery. In contrast, 12.0 V (as shown on cig-ligher voltmeter on the photo above) suggests the battery is significantly discharged, potentially even failing and requires immediate attention (charging or replacement). This seemingly small difference of 0.7 V represents a major shift in state of charge, easily over 70%.
So, if the voltage measurement method (through a cigarette lighter socket) introduces an error margin that large, it can render the reading unreliable and potentially misleading, making a good battery appear bad, or vice versa. In such cases, the convenience of the method doesn’t justify the risk of misinterpretation.
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Pardon my intrusion here, as I am certainly not any kind of automotive expert.
However, it seems to be after reading this thread that the objections to using something like a voltmeter plugged into the cigarette lighter socket are kind of uncalled for.
This because of what seems to be the OP's motivation here:
I just had the idea to get one of these due to not trusting the intermittent battery light so then I can monitor the actual voltage when driving without having to pop the hood at a layby and check manually when that light is coming on and off.
I have been monitoring it more regularly now after driving and so far have not seen any decline in voltage when I park up so doesn't seem to be an indicator of battery drainage.
Having something like this I feel would give peace of mind as regardless, of the light not having correlated with actual battery malfunction yet, it does make me twitchy each time it decides to come on while driving.
Now, they didn't say what kind of accuracy they were aiming for; they'll have to tell us this themselves.
But it seems like they want something a little better than a "go/no go" indicator.
I don't think the voltage drop caused by whatever wiring there is betwixt battery and cig-lighter socket would be significant here. The relative voltage indications between a battery in a known-good state and otherwise should be sufficient for their purposes.
I'll let them (the OP) speak for themself to clear this up.
Exactly my point.
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I don't think the voltage drop caused by whatever wiring there is betwixt battery and cig-lighter socket would be significant here. The relative voltage indications between a battery in a known-good state and otherwise should be sufficient for their purposes.
the concern here lies in the precision required to meaningfully assess battery condition or charging voltage. Even a deviation as small as 0.2-0.5 V can lead to a completely incorrect interpretation. Typically you need < 0.1 V error for a good lead acid battery assessment.
For example, a resting voltage of 12.7 V typically indicates a fully charged and healthy lead-acid battery. In contrast, 12.0 V (as shown on cig-ligher voltmeter on the photo above) suggests the battery is significantly discharged, potentially even failing and requires immediate attention (charging or replacement). This seemingly small difference of 0.7 V represents a major shift in state of charge, easily over 70%.
So, if the voltage measurement method (through a cigarette lighter socket) introduces an error margin that large, it can render the reading unreliable and potentially misleading, making a good battery appear bad, or vice versa. In such cases, the convenience of the method doesn’t justify the risk of misinterpretation.
Wrong, again.
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I really doubt that the OP needs a solution with Coulomb-counting and Peukert compensation, just something better than an idiot light. On my cars I keep a cheap "cigarette-lighter" combo USB-charger / voltmeter plugged in. I occasionally glance at it before I crank over the starter, and perhaps turn on the headlights to check the non-charging battery voltage. Then I start the car and watch to see if the voltmeter shows the battery voltage jump up appropriately. This isn't a precision test of battery condition or voltage, but it warns me of impending problems. More than good enough for my needs.
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Wrong, again.
Simply stating "wrong" without explaining your reasoning doesn’t help move the discussion forward. If you believe something is incorrect, it would be far more constructive to clarify why - ideally with technical details or a practical example. That way, we can have a more productive and informed conversation.
Otherwise, such comments come across as typical trolling behavior - dismissing any opposing viewpoint with a blanket "wrong, again" without offering any substance in return. It looks you're trying to reject any statement without engaging in real discussion. But that approach doesn't hold up in a technical or reasoned debate, where disagreement should be supported by clear, evidence-based arguments - not just empty claims with nothing behind them.
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2023 Tacoma
Accessories on
Fan full blast
1) Engine off, at battery
2) Engine off, at lighter socket
3) Engine running, at battery
4) Engine running, at lighter socket
Maximum of about 1% voltage drop between battery and lighter socket.
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Wrong, again.
Simply stating "wrong" without explaining your reasoning doesn’t help move the discussion forward. If you believe something is incorrect, it would be far more constructive to clarify why - ideally with technical details or a practical example. That way, we can have a more productive and informed conversation.
Otherwise, such comments come across as typical trolling behavior - dismissing any opposing viewpoint with a blanket "wrong, again" without offering any substance in return. It looks you're trying to reject any statement without engaging in real discussion. But that approach doesn't hold up in a technical or reasoned debate, where disagreement should be supported by clear, evidence-based arguments - not just empty claims with nothing behind them.
Instead of repeating that old song of you, you better start reading and trying to understand what some of us are explaining you.
Stop trolling.
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2023 Tacoma
Accessories on
Fan full blast
1) Engine off, at battery
2) Engine off, at lighter socket
3) Engine running, at battery
4) Engine running, at lighter socket
Maximum of about 1% voltage drop between battery and lighter socket.
It’s as simple as that.
:-+
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BillyO, the Tacoma, seeing below 12.0V terminal voltage on the battery, I think is a problem- that's saying the battery's State of Charge is low roughly 25-40%. I would say the battery needs a decent manual charge and equalization.
I find it's a common problem with modern vehicles - the parasite drains can leave the battery partially charged. Firmware updates to Body Control Module etc. better that, but sometimes a module can't go to sleep because something is hanging it up. Subaru's are notorious for killing batteries 3yr life due to the high parasite drain 75-100mA.
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BillyO, the Tacoma, seeing below 12.0V terminal voltage on the battery, I think is a problem- that's saying the battery's State of Charge is low roughly 25-40%. I would say the battery needs a decent manual charge and equalization.
I find it's a common problem with modern vehicles - the parasite drains can leave the battery partially charged. Firmware updates to Body Control Module etc. better that, but sometimes a module can't go to sleep because something is hanging it up. Subaru's are notorious for killing batteries 3yr life due to the high parasite drain 75-100mA.
Or a decent (long) drive. but it won’t change the amount of parasitic drain.
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I really doubt that the OP needs a solution with Coulomb-counting and Peukert compensation, just something better than an idiot light. On my cars I keep a cheap "cigarette-lighter" combo USB-charger / voltmeter plugged in. I occasionally glance at it before I crank over the starter, and perhaps turn on the headlights to check the non-charging battery voltage. Then I start the car and watch to see if the voltmeter shows the battery voltage jump up appropriately. This isn't a precision test of battery condition or voltage, but it warns me of impending problems. More than good enough for my needs.
You're right, this doesn’t require a precision instrument at all. Even an old one-dollar DT830 DMM would be sufficient for the task. But the key point here is that if you're aiming to assess the actual condition of the battery, not a reading affected by voltage drops or wiring issues, then you need to measure directly at the battery terminals. This does not require a super-precision measuring device, you just need to understand what you want to measure and how best to do it.
If you're using the cigarette lighter socket, it’s important to understand that the voltage you see does not reflect the true battery voltage.
A voltmeter in the cigarette lighter isn’t significantly more reliable than a simple indicator LED. I could demonstrate a scenario where such a voltmeter would display, say, 6 V instead of the actual 12.7 V at the battery terminals, and I’m sure you can imagine how that could be done.
In practice, I’ve encountered multiple cases where such kind of gadgets provide inaccurate or misleading readings, so I don’t even bother looking at them to not spend the time. Even though my car reports battery voltage over the CAN bus, which I can view both on my smartphone via Bluetooth and on the remote control from the security system, I don't rely on those when I need to check the actual battery state. I always go straight for the DMM and measure directly at the terminals under the hood.
That said, for convenience, it's sometimes useful to glance at the remote display without leaving the house. But I always keep in mind that these values can differ from the real voltage, and based on experience, I have a general idea of how much deviation to expect.
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Maximum of about 1% voltage drop between battery and lighter socket.
It’s as simple as that.
:-+
Are you aware that this 1% can easily turn into 10%, 50%, or even 100% error just depending on the condition of your vehicle’s wiring? What may look negligible under ideal circumstances can become highly misleading as connectors age, corrosion builds up, or contact resistance increases. So relying on such measurements without considering these variables can lead to false confidence.
That’s why, to avoid chasing false leads and wasting time on unnecessary checks, the best approach is to connect a voltmeter directly to the battery terminals. This gives you a reliable, unambiguous reading - one that’s unaffected by wiring issues or contact resistance, so you can be 100% certain of the actual voltage at the battery itself.
Since even a 0.1 V drop can be critical for any reasonably accurate assessment of battery condition (especially for load-test), I don’t even consider solutions that involve measuring voltage somewhere along the vehicle’s wiring. Only direct measurement at the battery terminals can provide the level of accuracy needed for meaningful diagnostics. There is no other reliable solution.
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I think you're pretty much in a minority of one here.
Still waiting to hear back from the OP.
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BillyO, the Tacoma, seeing below 12.0V terminal voltage on the battery, I think is a problem- that's saying the battery's State of Charge is low roughly 25-40%. I would say the battery needs a decent manual charge and equalization.
I find it's a common problem with modern vehicles - the parasite drains can leave the battery partially charged. Firmware updates to Body Control Module etc. better that, but sometimes a module can't go to sleep because something is hanging it up. Subaru's are notorious for killing batteries 3yr life due to the high parasite drain 75-100mA.
Or a decent (long) drive. but it won’t change the amount of parasitic drain.
I found a long drive does not help. You have to overcharge a bit, have higher voltage for the flooded types like that in the Tacoma. I find 14.4V is a reasonable top-up, and I never see that in a car (summer time) for more than a minute or two after starting. Some manufacturers advise going to 16.2V for equalize until charging current drops or after an hour max.
One car had one cell constantly needed more water than the others, took me years to realize that cell was just way off from the others. The car's charging system never fixed it.
I manually charged it and years later it's using the same amount of water as the other cells, doing fine.
Most people I know are having to manually top-up charge their car battery. The problem is auto makers don't realize an old or cold battery needs more charging - charge efficiency drops yet the ECU (battery model) does not provide more, so you are constantly losing, it's starved.
I've seen Volkswagen ECU's require you program the battery type (AGM, Wet etc.) and Ah capacity. So it's getting complicated nowadays.
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Subaru's are notorious for killing batteries 3yr life due to the high parasite drain 75-100mA.
That's quite a lot - my car draws about 30 mA and I think most of it is due to the security system. It periodically transmits a beacon to maintain communication with the remote control unit and I estimate it accounts for around 20 mA.
But a 3-year battery life is fairly typical, mostly due to insufficient maintenance. It needs to be fully charged periodically, but most people simply don’t do that.
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When the alternator starts running, it’s often charging the battery at 14,4V.
When we sell or replace a car battery, we always charge it well before handing over.
We used to fill batteries also, but that we don’t do anymore.
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BillyO, the Tacoma, seeing below 12.0V terminal voltage on the battery, I think is a problem- that's saying the battery's State of Charge is low roughly 25-40%. I would say the battery needs a decent manual charge and equalization.
I find it's a common problem with modern vehicles - the parasite drains can leave the battery partially charged. Firmware updates to Body Control Module etc. better that, but sometimes a module can't go to sleep because something is hanging it up. Subaru's are notorious for killing batteries 3yr life due to the high parasite drain 75-100mA.
Or a decent (long) drive. but it won’t change the amount of parasitic drain.
No Worries,
That's under a heavy load. Lights on, accessories on, fan on full blast, cabin lights on, infotainment system on, ignition system on, computers on. it's a 2023 TRD Sport, so LED lights are few and far between. So probably drawing well over 40A. That battery is less than 2 years old and has zero problems starting the engine.
I can put it on a trickle for a few hours though.
Edit: Just measured it with quiescent load @ 12.32V, so yeah, it could you a few hours on a trickle charger.
BTW, my wife's 2017 Honda Civic is still on it's orignial battery too.
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But a 3-year battery life is fairly typical, mostly due to insufficient maintenance. It needs to be fully charged periodically, but most people simply don’t do that.
My last car was a 2008 Ridgeline bought new in 2007. I replaced the battery once in 16 years.
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I think you're pretty much in a minority of one here.
Thanks. I consider it a compliment. Being in the minority means you're thinking independently and in technical matters, the majority is frequently wrong simply because the average expertise of a crowd is, statistically, quite low.
As for measuring battery voltage, in my view, this has nothing to do with popular opinion - just because Ohm’s Law operates independently of what the crowd believes about it. :)
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I replaced the battery once in 16 years.
:o
That sounds incredible - what type of battery are you using?
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The first battery is whatever Honda put in it. Yuasa? I replaced that with an Interstate.
Like I also said in a recent edit, my wife's Civic is going on 8 years on the original battery.
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Being in a minority generally means being wrong.
Just like the crazy ones think they’re right.
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Our tech support at headquarters (Bosch) does admit that the original battery in a car is often/almost always lower quality then after market.
Lots of issues with agm type batteries.
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Battery longevity data point:
My current battery is 6-1/2 years old, still going strong, absolutely no problems.
And I live in a place with cold winters.
No special brand, bought it at a discount place.
(car = Nissan Cube)
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Our tech support at headquarters (Bosch) does admit that the original battery in a car is often/almost always lower quality then after market.
Lots of issues with agm type batteries.
I wouldn't say Yuasa batteries are low quality. Probably one of the best batteries worldwide. IIRC, the Interstate (renowned for quality too, at least in NA) was about $175 less than the Yuasa at the time. Something like $450 vs $275.
Edit: It's also interesting to note that my Austrian KTM motorcycle came with a Yuasa battery too, rather than a Bosch.
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Those brands are unknown to me, probably true for Europe in general.
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Being in a minority generally means being wrong.
Just like the crazy ones think they’re right.
Yes, that may be true in some rare cases, but not as a rule. History offers countless examples where the minority view initially dismissed or ridiculed turned out to be correct. Scientific and technological progress is usually driven by those who challenge the consensus and think differently.
What is important is that simply being in the minority doesn’t make someone right, but it certainly doesn’t make them wrong either. What ultimately matters is the strength of the evidence, not how many people agree.
The truth isn’t determined by the number of voices behind it, it’s determined by logic, facts, and evidence.
To me, the majority opinion usually reflects the views of the most stupid segment within crowd (this can be easily approved statistically). Arguments based solely on majority agreement come across as if you’re saying "I’m right because my opinion matches that of the most stupid peoples in the crowd". This doesn’t necessarily mean that such an opinion is always incorrect, no it just reflects the perspective of the most stupid segment of the crowd. The reasons behind such opinions among can vary - they may stem from manipulation or simply from ignorance, etc. Regardless, the essence remains the same - it represents the opinion of the most stupid peoples of the group.
What I’m genuinely curious about is why the opinion of the most stupid peoples of the crowd holds such a high priority for you? :)
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That's a rather iffy proposition, at best: that the majority view constitutes the stupidest one, the opinion of the great unwashed masses. Because why?
Just as iffy as saying that the majority view must be the correct one because, hey, most everyone agrees with it.
Just accept that in this particular instance, you're the outlier.
(We still need to hear from the OP on this. How accurate is accurate enough for you?)
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Our tech support at headquarters (Bosch) does admit that the original battery in a car is often/almost always lower quality then after market.
That's interesting - in my experience, the original battery that came with my Toyota actually seemed more robust than any aftermarket one I've had since. It survived 4-5 full discharges within 4 years and still performed reliably. I eventually gave it to a friend, assuming it was near the end of its life, but it kept working flawlessly for several more years. In total, it lasted around six or even more years, which is better than most replacements I’ve tried.
My current battery is a Bosch, now about five years old. However, due to the war it is sitting unused most of the time. It's still functional, but based on the voltage behavior, it’s showing signs of aging - it used to hold 12.7 V for a long time, but now it drops to around 12.5 V relatively quickly and stabilizes there.
Overall, my impression of the Bosch battery hasn’t been particularly positive. It has always felt somewhat weak, and throughout its use I’ve had the sense that it was on the verge of failing - yet, somehow, it has managed to last five years and still working, recently we had 24 hours power outage and it helped me a lot, because I forgot to charge my power banks.
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Well, if you take every man, woman and child in the US (not including illegal immigrants) into account, then only 18% of those actually did the totally stupid thing of voting in the deranged orange dung pile. While that in itself does not disprove that the majority are stupid, it is a data point of evidence to that point.
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I would argue that the issue is not who people voted for, but the very act of voting itself. Regardless of the candidate chosen, anyone who participates in the electoral process implicitly accepts and legitimizes the authority imposed by the system, effectively consenting to be governed by whoever wins, regardless of their qualifications, character, or how they came to power, honestly or not. This is real indicator of stupidity.
The critical point is that by voting, individuals voluntarily submit to a structure of imposed power rather than questioning or challenging the legitimacy of that authority. And moreover, the fact that the majority still participate in elections suggests, in my view, proof that most people are stupid and lack critical awareness and are therefore, easily led - effectively endorsing a system where they are assigned the role of subjects or "servants" to the ruling class.
Even the act of casting a ballot holds symbolic significance: by placing their vote into the ballot box, individuals symbolically consign their opinion to the trash bin, implicitly acknowledging its disposability and futility.
However, to recognize that the majority of people are stupid, it is not necessary to invoke politics - mathematics alone suffices. In any sufficiently large sample, intelligent individuals will constitute a minority, while the stupid will form the majority. No matter how large the sample, you will observe a normal distribution, with relatively few highly smart people and a predominance of stupid. Consequently, the prevailing opinion within such a group tends to reflect the views of the stupid majority rather than smart minority.
And you cannot change this, because this is a fundamental mathematical characteristic of our world. :)
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effectively consenting to be governed by whoever wins
I imagine some of your reply has been borrowed, but this statement in particular would need some serious justification. History provides us ample evidence that this is not the case. Revolution is and always will be an option that effectively nullifies your assertion.
However, as interesting as a deep discussion regarding the philosophy of democracy is, it represents a considerable drift in the subject of this thread.
I apologize for starting this. I'll give you the last word on this "side-track". Perhaps "derailment" might be a more apropos term.
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This particular model will display two decimals below 10.0 volts, but even a single decimal is enough for general purpose battery monitoring.
Your photo shows 12.0 V, which is quite low and potentially concerning. If the engine is off and there's no charging, this voltage indicates a low state of charge - roughly around 30%. A healthy, fully charged battery should read about 12.7 V at rest (no load, no charging).
After charging, the battery may retain higher voltage for some time (due to internal chemical processes), which gradually stabilizes to its true open-circuit voltage 12.7 V over the course of approximately 30-40 hours.
If the engine is running and charging is active, you should typically see 13.0 to 14.4 V, depending on the vehicle and temperature.
The engine wasn’t running, and the car had been parked for a couple of days. Additionally, I had to readjust the power seat because my wife had previously driven it and she is significantly shorter than I am.
When the engine is running, it jumps to 14.1 V.
And to maintain my sanity, every now and then I open the bonnet and measure the voltage across the battery terminals.
My primary reason for adding this meter is precisely to determine how much the voltage is depleted when the vehicle is parked. We travel a lot, and is not uncommon to be away from home 10 to 15 days.
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I would argue that the issue is not who people voted for, but the very act of voting itself. Regardless of the candidate chosen, anyone who participates in the electoral process implicitly accepts and legitimizes the authority imposed by the system, effectively consenting to be governed by whoever wins, regardless of their qualifications, character, or how they came to power, honestly or not. This is real indicator of stupidity.
So you're saying essentially that voters are stupid.
I'd say it's looking more and more like you are the stupid one here.
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So you're saying essentially that voters are stupid.
Yes, I do consider the act of voting - particularly without a deeper understanding of what is being legitimized - to be a sign of very stupid people. A thoughtful and critically minded person is unlikely to endorse a system that grants power over their life to someone they don’t even know personally, based purely on campaign slogans or media representation.
Imagine a scenario where 10 wolves and 3 sheep are sitting at a table, voting on what's for dinner. The wolves participation is understandable - they know exactly what they’re doing and are acting in their own interest.
But what about the sheep? Can we consider a sheep smart for simply taking a seat at that table and participating in such a vote? Or does the very act of joining that process raise serious questions about its stupidity?
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I think you just painted yourself into a corner there, pal.
Be careful where you track those footprints as you steal your way out of there ...
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You mentioned I’ve "painted myself into a corner" but I’m genuinely curious - what exactly do you see as the corner, and why would I need to get out of it?
From my point of view, it's entirely rational to point out how flawed it is to participate in a process where the outcome is designed to serve interests other than your own. In a system where the act of voting serves primarily to legitimize authority - regardless of who wins, the voter effectively consents to be governed by whoever is chosen. Whether the winning candidate is the one you supported or not becomes irrelevant, because by voting, you’ve already accepted the rules of the game and agreed to the result in advance.
In that sense, participation itself is the trap - the real corner and the wisest choice is to avoid stepping into it in the first place.
In this context, the sheep demonstrates its lack of judgment simply by agreeing to participate in the process. The specific choice it makes - regarding who should be eaten for breakfast - is entirely irrelevant, because the outcome of such a game is predetermined from the start. What the wolves needed was not the sheep's vote, but its participation - to ensure that it would voluntarily accept the result. As for who the sheep actually voted for, the wolves couldn’t care less.
We seem to have strayed quite far from the original topic. It appears your goal is to catch me in some flaw in my reasoning. However, the issue is not that I invented these ideas, I am merely paraphrasing thoughts articulated by renowned philosophers of antiquity.
In fact, by attempting to prove that the minority is always wrong, you fall into a trap yourself - appealing to the majority opinion as an authority. Logic is not determined by the number of opinions supporting it but is founded on sound reasoning. The quantity of people endorsing a particular idea is irrelevant, what truly matters is the validity of the logic, which remains constant regardless of how many individuals support or reject it. It seems obvious to me, doesn't it?
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You mentioned I’ve "painted myself into a corner" but I’m genuinely curious - what exactly do you see as the corner, and why would I need to get out of it?
You just don't get it, do you?
Like my dear departed dad used to say (too often) to me: "Quit while you're ahead".
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"Quit while you're ahead".
Is he ahead?
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"Quit while you're ahead".
Is he ahead?
Nope, and that's the irony of it.
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You mentioned I’ve "painted myself into a corner" but I’m genuinely curious - what exactly do you see as the corner, and why would I need to get out of it?
From my point of view, it's entirely rational to point out how flawed it is to participate in a process where the outcome is designed to serve interests other than your own. In a system where the act of voting serves primarily to legitimize authority - regardless of who wins, the voter effectively consents to be governed by whoever is chosen. Whether the winning candidate is the one you supported or not becomes irrelevant, because by voting, you’ve already accepted the rules of the game and agreed to the result in advance.
In that sense, participation itself is the trap - the real corner and the wisest choice is to avoid stepping into it in the first place.
In this context, the sheep demonstrates its lack of judgment simply by agreeing to participate in the process. The specific choice it makes - regarding who should be eaten for breakfast - is entirely irrelevant, because the outcome of such a game is predetermined from the start. What the wolves needed was not the sheep's vote, but its participation - to ensure that it would voluntarily accept the result. As for who the sheep actually voted for, the wolves couldn’t care less.
I will point out that since quite a bit less than half of the eligible voters did vote either way, by your logic Americans are by and large smart. I find that a foolish conclusion and disagree with your other observations.
But I really read through the through the thread (very rapidly) interested in the OPs question and find that everyone's comments are directed towards the OP's assumption that there might be a battery problem.
My own reaction to the situation is that given sufficient understanding the OP might get a better understanding of his system electrical problem with a voltmeter at the cigarette lighter or any other convenient point. Three digit accuracy should be plenty, and the goal should not be limited to attempting to assess the battery state of charge, but what, if any problems exist in the system. It could be something faulty with the idiot light.
For example, bad connections at the battery terminal will cause voltage drops throughout the system under load. A bad enough connection will result in a low voltage engine off due to whatever small loads exist, but the voltage will rise unrealistically fast when the engine starts and the alternator kicks in (in many, perhaps most cases the maximum alternator current won't drive the battery internal impedance hard enough to bring a severely low battery up to full charging voltage immediately). Another situation I have run into repeatedly is that there are multiple taps off the positive battery terminal. Sometimes there is high contact resistance in some of the taps, and not others. The OPs idiot light might be attached to such a tap. Finding an appropriate voltage at the cigarette lighter or other test point could give a false sense of security, since there might be something more important than the idiot light on the same circuit.
Diagnosing all of the possibilities requires quite a bit of understanding of the electrical system of the specific vehicle, and at least a rudimentary understanding of ohms law and how much current flows in each of the circuits. This may or may not be in the OP's wheel house.
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I will point out that since quite a bit less than half of the eligible voters did vote either way, by your logic Americans are by and large smart. I find that a foolish conclusion and disagree with your other observations.
I’m not deeply familiar with the specifics of the American electoral system and don’t wish to delve into it. I view all these systems largely as a spectacle, where the core purpose is the act of participation itself - to legitimize the outcome.
Consider loyalty programs in large retail chains. Customers are encouraged to join and actively participate by collecting points and redeeming rewards. The core purpose isn’t necessarily to offer genuine value to each individual, but to create the appearance of engagement and loyalty. The act of participation itself legitimizes the program and keeps customers invested, even though the actual benefits may be minimal or structured to primarily serve the retailer’s interests.
For example, bad connections at the battery terminal will cause voltage drops throughout the system under load. A bad enough connection will result in a low voltage engine off due to whatever small loads exist, but the voltage will rise unrealistically fast when the engine starts and the alternator kicks in (in many, perhaps most cases the maximum alternator current won't drive the battery internal impedance hard enough to bring a severely low battery up to full charging voltage immediately). Another situation I have run into repeatedly is that there are multiple taps off the positive battery terminal. Sometimes there is high contact resistance in some of the taps, and not others. The OPs idiot light might be attached to such a tap. Finding an appropriate voltage at the cigarette lighter or other test point could give a false sense of security, since there might be something more important than the idiot light on the same circuit.
Diagnosing all of the possibilities requires quite a bit of understanding of the electrical system of the specific vehicle, and at least a rudimentary understanding of ohms law and how much current flows in each of the circuits. This may or may not be in the OP's wheel house.
Exactly, that is precisely the point I have been making - to properly test a battery, measurements must be taken directly at the terminals. This approach allows us to verify the battery’s condition in one step, if the battery is ok, we can then proceed to examine the wiring. Otherwise, measuring voltage at the cigarette lighter or elsewhere does not provide certainty about whether the battery or the wiring is functioning correctly. In other words, such measurements lack a reliable reference point to determine what is truly operational and what is not.
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How did we end up at politics over fitting a battery voltmeter?
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Selected one of the many digital voltmeters available online, trimmed the lead wire to proper length, attached a cigarette-lighter plug, double sticky tape, and in less than 15 minutes you are good to go.
This particular model will display two decimals below 10.0 volts, but even a single decimal is enough for general purpose battery monitoring.
I am not understanding all these suggestions to plug it in anywhere. As is mentioned by some others, how will that tell me the voltage of the battery if it isn't connected directly?
I don't see how if it is only plugged into the lighter terminal that it could tell me the overall voltage of the battery? Is the idea that the whole system uses the battery and so it will show the voltage wherever you have a circuit to it?
I agree that it doesn't have to be super accurate but I also want to see the voltage increases when it should be charging with the alternator. Does the voltage rise and fall even for the other appliances in the starter batteries' system?
I am most familiar with leisure battery/lifepo4 electrics. I had never really thought about it though if the voltage is rising and falling for all things connected when the solar is rising it through charging, for example. Is that the case?
Another thing I did think of though, is that if connecting to the wire the dc-dc charger also uses then wouldn't that blow the voltmeter as there are high amps going through that or would it only draw as much as it required, with a low amp fuse on that line of course? If there will be 40+ amps flowing through that circuit on the main battery wires when the dc-dc charger is running is there still a way to have the voltmeter connected and not have it blow as this would be very convenient to wire it to this existing circuit?
There seem to be two issues which are being conflated so far:
-where it should be connected to power the device.
-where it should be connected to give accurate voltage readings for the starter battery.
I mentioned connecting it between the starter battery and dc-dc charger circuit because that is connected directly to the battery and also the wire runs between the engine compartment and into the van.
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without knowing a lot more detail about the exact wiring it's hard to advise you on this.
See this (https://www.eevblog.com/forum/beginners/ok-to-make-direct-connection-between-vehicle-and-leisure-battery-in-a-scrape/) previous thread where there is a wiring diagram. One by myself in the attachment of the OP and also an amended one by another user later on as apparently my original one was hard to understand and not formatted in the usual way, which I am not familiar with.
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The idea is to know whether the battery is being charged or not.
You do t need a 6.5 digit meter for that nor any exact battery voltage as any 12V power line will tell you if there is a problem or not.
You're right that any significant voltage drop typically indicates a problem - but only if you're measuring at the correct point. That’s exactly why connecting a voltmeter anywhere other than directly at the battery terminals can be misleading.
In a vehicle, wires and connections are exposed to vibration, moisture, corrosion, and mechanical wear. A wire might be partially damaged, corroded, or have a poor contact, which can create resistance. As a result, the voltage at some 12V line inside the vehicle might appear low - making it seem like the battery is undercharged - even if the battery is actually in perfect condition. Or worse, it might appear normal while the battery is failing, simply because you're measuring after a faulty connection.
If your goal is to know whether the battery itself is being charged, and what its voltage is under various conditions, then the only reliable method is to measure voltage at the battery terminals. This eliminates the influence of unknown or degrading vehicle wiring and ensures you're seeing the true battery status - not what’s happening downstream at, say, the cigarette lighter or a fuse panel.
In short: if you want to monitor the battery, measure at the battery. Anything else may tell you more about the wiring than the battery itself.
But even a voltmeter will not tell you if there is enough charge in the battery.
a voltmeter alone won’t give you the full picture of battery health unless it's connected directly to the battery terminals and used properly.
When voltage is measured at the battery terminals, you can absolutely assess both the state of charge and get a good indication of the battery’s condition. Measurements taken elsewhere in the vehicle’s wiring, such as at a cigarette lighter or accessory circuit - are affected by wire resistance, voltage drops, and potential faults. These measurements not only fail to represent the actual battery voltage but can’t reliably indicate battery condition at all.
To evaluate state of charge, just let the battery rest for 30-40 hours at ~25°C without any load or charging. Then measure the open-circuit voltage directly at the battery terminals. This gives you the battery’s EMF. Then you can estimate the charge level in percents with this simple approximation:
State of charge (%) = (Voltage - 11.7) * 100
To assess internal resistance, again connect the voltmeter directly to the terminals. Measure the voltage with no load, then under a significant load (e.g., headlights + heater).
Even without measuring current, a large voltage drop under load indicates high internal resistance - a sign of battery aging or failure.
But notice very important thing - in all cases, reliable conclusions require voltage measurement directly at the battery terminals. Anything else may mislead you due to unknown wiring losses or faults.
This reply goes in to great detail as to my confusion mentioned in post above as to why many are recommending to just plug it in anywhere. You explained it far better than I could have. It doesn't have to be pinpoint accurate but it certainly has to be taking its readings from the right place!
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electroniclearner820327, intermittent battery light is on the vehicle's instrument cluster, but not sure what a "cab" means in the UK. What vehicle is this? Here a cab=taxicab. Some semi trucks (24V) have a cab though.
It just means being able to monitor inside the dashboard/cockpit of the vehicle. Cab = where you are sitting when driving.
The alternator lamp can caused by many things, usually it's the brushes worn out, a belts, bad connection- that causes the alternator to intermittently cutout. Check the wiring - including the battery terminals. Very important.
Well as I have written, I have been monitoring it for a while now, both with the vehicle running and when off and the alternator seems to be working fine from the readings I get from when I look manually with a voltmeter. So I think the light is a false positive, at least for alternator charging. In my other threads I detail how the general electrics of the whole van acts in weird ways and thinking this might just be part of it. Still, for peace of mind, I would like an independent voltmeter so I can keep an eye on the voltage without having to go to the trouble of always opening the hood to check myself with the
A modern vehicle has ECU-control and there are many extra reasons for the light to come on. Overheating alternator (plugged vents), voltage too high or low, no output, battery voltage low, overcurrent etc.
You can buy cheap voltmeters for a couple pounds from Aliexpress (https://www.aliexpress.com/w/wholesale-car-voltmeter.html?g=y&SearchText=car+voltmeter) or eBay etc.
Yea I just saw they have them available from the online electrical shop I use regularly and I have just purchased some other kit so will add one too the cart. Only £3 something. Much better than the overpriced one of almost £20 I linked in the OP!
It is like when I bought usb sockets for my van before I knew you could get them for only a couple of £ from electrical shops. Paid about £50 for a name brand for a 2 port and then months later I see I could have bought bare ones for like £3. :-\
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When I tried to get clarity on what was going on, he was defensive, insisting that he was a certified engineer and knew what he was doing, citing service procedures and internal regulations. Eventually, I managed to get enough information from him to understand the root of the problem - and it became clear almost immediately.
This is a problem I have had when trying to get guarantee support for one of my pieces of equipment. The company is famous for its founder being extremely rude to customers. They are very responsive to queries however they have incredible egos about their products such that they ignore data I am trying to give them and just reply with things they think it must be which I already tried multiple times. They told me that 'intermittent problems don't really happen with our products' and so would ignore stuff I was telling them and I knew they were writing it all off as user error.
Looking online it is a love or hate thing with many having similar experiences to me with others never having had issues and singing their praises.
With a lot of fiddling about I managed to figure out the behaviour over the months and make it work despite these issues they tell me cannot exist. It does work well when it works so I am not pushing to get it sent replaced as I know they would also say it works fine. I already sent it back once for testing and they didn't find an issue and so I put it back in and it worked fine for a couple of days and the problems arose again.
The device is very finecky and I have started to find ways to work around its idiosyncrasies.
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Sorry but this is a kind of nonsense.
I have been analyzing car electronics and car battery issues for more than 20 years.
You can reliably measure the battery voltage at any point in the car.
Exactly!
@Radiolistener is speaking too theoretically. Yes, you can and will get voltage drops across bits of the wiring loom, but I'm pretty sure @radiolistener has never worked on car electrics because - for the OP's purpose - this is just too trivial to worry about. Also, someone said that the battery will measure from 13.0V upwards if it is charging. No, it wont. It will measure from 13.8V upwards, but usually significantly over 14V. I've got three cars; one of them reads 14.1V on charge, the other two are 14.4V.
The OP just wants some indication of whether the battery is still being charged when the warning light comes on. A voltmeter plugged into the cigarette lighter socket would be fine for that purpose. We are talking about a minimum of 1V difference between charging and not charging, and most likely 1.5V or more.
The OP can see for himself what the typical readings are between charging and not charging. Switch on the ignition and read the meter. Then start the engine and read the meter. The fault is intermittent, so the OP can see for himself what the typical "charging" voltage is.
Some people in this thread are making a mountain out of a molehill!
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But even a voltmeter will not tell you if there is enough charge in the battery.
I'm going to pull this out from page one, as it seemingly got lost in the noise.
Battery voltage *alone* is not a reliable indicator of condition, nor state of charge. Lead acid chemistry is 'complex', especially as batteries age and/or when they are damaged. I've two 45Ah lead acid AGM batteries in my garage, less than a year old. They have never been 'abused' but they have been frequently cycled. Both show ~13v off load (measured at the terminals), and ~12.7v when initially connected to a 4A DC electronic load. When measured using said load, one returns a capacity of ~4Ah, the other 10Ah i.e. they are 'done'. Both were 'fully' charged prior to testing.
Equally, about 13.5 to 14v or so (some regulators have temperature compensation) when your engine is running tells you only that the alternator and voltage regulator are doing their job. It says nothing as to whether the battery is actually accepting charge, and even less about how much it can retain.
If you're really concerned about charge and discharge rates, I think you'd be better off looking at something like this: https://www.victronenergy.com/battery-monitors/smart-battery-shunt (https://www.victronenergy.com/battery-monitors/smart-battery-shunt)
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Yes, I do consider the act of voting - particularly without a deeper understanding of what is being legitimized - to be a sign of very stupid people.
Everyone knows that democracy is the worst system of government, except for all the others, which are even worster. <sic>
So, @radiolistener, if you think people are stupid to partake in democracy, what form of government do you advocate?
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Pardon my intrusion here, as I am certainly not any kind of automotive expert.
However, it seems to be after reading this thread that the objections to using something like a voltmeter plugged into the cigarette lighter socket are kind of uncalled for.
This because of what seems to be the OP's motivation here:
I just had the idea to get one of these due to not trusting the intermittent battery light so then I can monitor the actual voltage when driving without having to pop the hood at a layby and check manually when that light is coming on and off.
I have been monitoring it more regularly now after driving and so far have not seen any decline in voltage when I park up so doesn't seem to be an indicator of battery drainage.
Having something like this I feel would give peace of mind as regardless, of the light not having correlated with actual battery malfunction yet, it does make me twitchy each time it decides to come on while driving.
Now, they didn't say what kind of accuracy they were aiming for; they'll have to tell us this themselves.
But it seems like they want something a little better than a "go/no go" indicator.
I don't think the voltage drop caused by whatever wiring there is betwixt battery and cig-lighter socket would be significant here. The relative voltage indications between a battery in a known-good state and otherwise should be sufficient for their purposes.
I'll let them (the OP) speak for themself to clear this up.
Radiolistener's post below echoes my thoughts on the matter very well. If it is correct that there can be such variance as stated below then that can mean the difference between a battery that can start and one where you would be left stranded thus causing a false sense of confidence.
You mention better than "go/no go" well that doesn't seem much better if at all. The whole point is to not get a false positive/negative as with the battery light and with such variance it seems it would be a very similar situation.
I don't think the voltage drop caused by whatever wiring there is betwixt battery and cig-lighter socket would be significant here. The relative voltage indications between a battery in a known-good state and otherwise should be sufficient for their purposes.
the concern here lies in the precision required to meaningfully assess battery condition or charging voltage. Even a deviation as small as 0.2-0.5 V can lead to a completely incorrect interpretation. Typically you need < 0.1 V error for a good lead acid battery assessment.
For example, a resting voltage of 12.7 V typically indicates a fully charged and healthy lead-acid battery. In contrast, 12.0 V (as shown on cig-ligher voltmeter on the photo above) suggests the battery is significantly discharged, potentially even failing and requires immediate attention (charging or replacement). This seemingly small difference of 0.7 V represents a major shift in state of charge, easily over 70%.
So, if the voltage measurement method (through a cigarette lighter socket) introduces an error margin that large, it can render the reading unreliable and potentially misleading, making a good battery appear bad, or vice versa. In such cases, the convenience of the method doesn’t justify the risk of misinterpretation.
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Battery voltage *alone* is not a reliable indicator of condition, nor state of charge.
<SIGH>
Yes, yes, everybody knows this! The OP is not trying to ascertain the battery condition. He is trying to see whether it is being charged or not. A simple voltage measurement is entirely adequate for that purpose.
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2023 Tacoma
Accessories on
Fan full blast
1) Engine off, at battery
2) Engine off, at lighter socket
3) Engine running, at battery
4) Engine running, at lighter socket
Maximum of about 1% voltage drop between battery and lighter socket.
It is thoughtful of you to do that test however you must also accept that is not going to do much to prove any kind of rule. My vehicle is much different from yours and I imagine much less reliable being almost 20 years older and already given the many electrical issues stated! So your case does not automatically transpose to mine.
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Battery voltage *alone* is not a reliable indicator of condition, nor state of charge.
<SIGH>
Yes, yes, everybody knows this! The OP is not trying to ascertain the battery condition. He is trying to see whether it is being charged or not. A simple voltage measurement is entirely adequate for that purpose.
indeed.
its funny to see how some get lost in a non-discussion.
it how's what their (lack of) practical experience is worth.
And even more funnier, the TS fell into that hole also.
Like he did in his first topic.
People only see what they want to see.
As in politics |O
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I think you're pretty much in a minority of one here.
Still waiting to hear back from the OP.
Nope, it is a minority of 2 if that is the case. As I write above, radiolistener is my spokesperson and saying almost exactly what I am thinking but in a much more informed way. 8)
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As I write above, radiolistener is my spokesperson and saying almost exactly what I am thinking but in a much more informed way.
What, about the voltmeter, or about democracy?
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I just get a cheap battery powered DMM and the lghier plug. No mod and after a while if there is no problem you don't need it. With a 10 Megahohms input impdedance whatever resistance in the wiring harness is insignificant.
Hi,
I use the lighter plug too but it's better to wire direct to the battery terminals with an included inline fuse. There is no better way to monitor the battery voltage itself if you want the utmost accuracy.
The drop in voltage however is not related to the voltmeter current draw, it's due to the current draw from other items in the car such as the headlights, interior lights, etc. When the headlights turn on they could cause a drop in the harness voltage which would then mean the voltmeter could see less voltage also.
I've been using the lighter plug for some time now so I know how to interpret the readings. I make sure nothing else is turned on when I take the readings, and be sure to always do it that way. The readings I get are an indicator of how the electrical system is functioning because I know the history of all the readings I have taken over the years. If a problem comes up, it will still show up in the readings even though they may not be 100 percent accurate.
So the bottom line we can say is if you use the cigar lighter jack then build up a history, and it might be a good idea for the first readings to compare with readings taken directly at the battery terminals, at the very same time as the readings from the jack are taken. Once a couple weeks go by you should have a good idea what the readings SHOULD look like with nothing else turned on.
I also do not recommend keeping the meter connected to the battery. Use a switch if needed. That's because some panel meters do draw some significant current. Even a couple milliamps is not a good idea.
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But even a voltmeter will not tell you if there is enough charge in the battery.
I'm going to pull this out from page one, as it seemingly got lost in the noise.
Battery voltage *alone* is not a reliable indicator of condition, nor state of charge. Lead acid chemistry is 'complex', especially as batteries age and/or when they are damaged. I've two 45Ah lead acid AGM batteries in my garage, less than a year old. They have never been 'abused' but they have been frequently cycled. Both show ~13v off load (measured at the terminals), and ~12.7v when initially connected to a 4A DC electronic load. When measured using said load, one returns a capacity of ~4Ah, the other 10Ah i.e. they are 'done'. Both were 'fully' charged prior to testing.
Equally, about 13.5 to 14v or so (some regulators have temperature compensation) when your engine is running tells you only that the alternator and voltage regulator are doing their job. It says nothing as to whether the battery is actually accepting charge, and even less about how much it can retain.
If you're really concerned about charge and discharge rates, I think you'd be better off looking at something like this: https://www.victronenergy.com/battery-monitors/smart-battery-shunt (https://www.victronenergy.com/battery-monitors/smart-battery-shunt)
The measurement of battery voltage is a fairly complicated thing, but there are some ways to simplify this.
For one, a single measurement at any time is probably not a good indicator of anything. However, a history of readings, especially under known conditions, is very good.
For a car battery, a good indicator is to measure the voltage while charging, but also to measure after the car engine is turned off, then also after the car has been sitting for a day or longer. If the voltage when the car is turned off is say 12.9v and the voltage after a day is 12.4v, it's probably doing ok, as long as that repeats to some degree day after day for a few weeks. If the car voltage is 12.9v and then after a day of sitting is 12.0v, that may mean the battery is either getting old or needs a good charge with a good charger. This is especially true if it goes below 12.0v after a day or maybe a few days.
If you let it sit for one day and see it go to a certain voltage, then watch for that behavior again and again. The point is to look for a change in behavior while measuring in the same way.
As above, there are two ways the battery voltage can get lower than usual. Either the battery is getting old, or the battery has been drained too low by sitting for too long. If it is old then there's no good way to help it except to charge it with a good charger and then keep checking it. If it is just drained too low, then charge it with a good charger and that could get it back to normal.
If the alternator is a good one, then just driving the car for a longer time could help charge the battery back to normal. That would be one that can put out maybe 14.8v to start. If it is an alternator that can only put out 14.0 volts, then a good charger will be needed to help get the battery back to normal.
These notes come after years of testing and monitoring the battery right in the car, and testing and monitoring using (for a long time) a solar charger system.
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My primary reason for adding this meter is precisely to determine how much the voltage is depleted when the vehicle is parked. We travel a lot, and is not uncommon to be away from home 10 to 15 days.
Similar but opposite case for me. I live in my van full-time but travel as little as I can get away with! Which means about once per week.
I only got a new battery last year and the one I had since I bought the van second hand a couple of years ago would be very reluctant to start after one week stationary. It totally died a few days after getting the dc-dc charger and then would not hold a charge thereafter even on mains which precipitated the replacement.
Just looking at my notes I have saved from previous checks it seems it discharges about 40-50% not running for the week and having checked again before setting off.
This is why I think it would be useful to have those jumper cables to give it a blast with the leisure battery if I ever happened to leave it drop to an unstartable state but from what I have read it can take 6 weeks for that with a relatively new battery? In those cases though people I think are talking about when their vehicle has been parked in storage without them using it whereas there will be more drain in my case since I am constantly getting in and out of the van I guess due to the auxiliary crap. Better to prevent it happening but those jumpers would be a nice safety net.
It hasn't happened yet but if it did get to that, to prevent in future I would think about getting an easy battery terminal remover or battery isolator switch for the starter to stop the parasitic drain. I would not mind opening with the keys rather than central locking. It is a horrid waste of energy anyway to be draining the battery like that constantly for no good reason so maybe something to think about either way. Just unplug when I have done my weekly drive and connect again when wanting to go.
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Battery voltage *alone* is not a reliable indicator of condition, nor state of charge.
<SIGH>
Yes, yes, everybody knows this! The OP is not trying to ascertain the battery condition. He is trying to see whether it is being charged or not. A simple voltage measurement is entirely adequate for that purpose.
indeed.
its funny to see how some get lost in a non-discussion.
You mean, like the dozen or so pissing contest / ego clash posts that preceded it?
Heaven forbid someone add something actually germane to a discussion in the beginners section.
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In fact, by attempting to prove that the minority is always wrong, you fall into a trap yourself - appealing to the majority opinion as an authority. Logic is not determined by the number of opinions supporting it but is founded on sound reasoning. The quantity of people endorsing a particular idea is irrelevant, what truly matters is the validity of the logic, which remains constant regardless of how many individuals support or reject it. It seems obvious to me, doesn't it?
While I retract my statement that you are my spokesperson as it has veered into this political discussion, I am not against the subject matter as I happen to have become very interested in political philosophy lately and having very in depth discussions on other more relevant forums.
I would not assent to much of what you are saying or at least it is not being put in a very good way but the general idea the majority doesn't = right then sure. An easy example of this would be how the german people were swept up with Nazism. The party were the majority then, did that make everything they said and did right? Countless other examples of tyrannical governments.
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lets keep off the politics please.
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The OP can see for himself what the typical readings are between charging and not charging. Switch on the ignition and read the meter. Then start the engine and read the meter. The fault is intermittent, so the OP can see for himself what the typical "charging" voltage is.
I have done this several times already and also as I have noted in my various posts about it the battery light being on seems to have no bearing on the state of charge as I have been able to check at the battery terminals directly when it is on and the engine is running and saw 13/4+ volts and the alternator running happily.
This is why I suspect it is a false positive hence why I would like a standalone voltmeter. Even if it is a false positive there is nothing to say it would not genuinely be lighting up at some point in the future and if I got used to ignoring it then it would be a case of the boy who cried wolf.
Now I don't really have a horse in this race about cigarette lighter or not but I do think I would prefer to rule out possible discrepancies compared to a direct connection. Just 'belt and braces' and I am skeptical there being an inconsequential difference and I don't care to do the testing to find out if it is the case or not and since it isn't that hard to setup directly and not that much cost then why not. Also a dedicated circuit leaves the lighter socket free and want this reading to be a constant fixture for the foreseeable.
I don't want it to be 'try for a few times then put it away' as someone else says. It has to stay there for the duration of the weird electrical issues which don't seem to be going anywhere any time soon. :-DD
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The OP just wants some indication of whether the battery is still being charged when the warning light comes on. A voltmeter plugged into the cigarette lighter socket would be fine for that purpose. We are talking about a minimum of 1V difference between charging and not charging, and most likely 1.5V or more.
When I need to verify if the battery is actually charging, I use a current clamp on the wire at the battery terminal and check the current direction and magnitude. I wouldn’t trust any conclusions based on a cigarette lighter voltmeter. :)
The OP can see for himself what the typical readings are between charging and not charging. Switch on the ignition and read the meter. Then start the engine and read the meter. The fault is intermittent, so the OP can see for himself what the typical "charging" voltage is.
No. What the OP will see on a voltmeter connected to the cigarette lighter doesn’t confirm whether the battery is charging at all. It only shows the voltage level at the vehicle’s electrical net at some point, which reflects a redistribution of potentials after starting the engine. This voltage increase doesn’t guarantee that current is actually flowing into the battery. Only a current measurement at the battery terminal can reliably confirm actual charging.
The OP is not trying to ascertain the battery condition. He is trying to see whether it is being charged or not. A simple voltage measurement is entirely adequate for that purpose.
Not necessarily. A voltmeter in the cigarette lighter cannot reliably indicate whether the battery is actually being charged. See description above.
Likewise, it does not indicate the actual state of charge of the battery. For example, in the photo above, the voltmeter shows 12.0V, and I seriously doubt this is the actual battery voltage. Such a low voltage would typically occur if the car had been left unused for 2-3 months and the battery had self-discharged. However, according to the author comments, the photo was taken after just a couple of days of downtime.
If the vehicle has only been parked for a week and shows this reading, something is clearly wrong - either with the battery itself or with the cigarette lighter voltmeter. I would suspect the problem is with the cigarete lighter voltmeter.
In fact, verifying that the battery is charging correctly is not as simple as it seems, and it certainly can't be done based on voltage readings taken somewhere in the vehicle's electrical system or even at battery terminals. To confirm proper charging, a current clamp on the battery terminal wire is required.
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I think you're pretty much in a minority of one here.
Still waiting to hear back from the OP.
Nope, it is a minority of 2 if that is the case. As I write above, radiolistener is my spokesperson and saying almost exactly what I am thinking but in a much more informed way. 8)
It is not that difficult to find 2 people that make up their own truth.
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One suggestion, to get most benefit from your effort, look into one of the inexpensive USB charging ports that includes a voltage monitor. Almost every needs/can use another charging port and you end up with a permanently installed voltmeter with adequate resolution. They are quite inexpensive.
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Yes, I do consider the act of voting - particularly without a deeper understanding of what is being legitimized - to be a sign of very stupid people.
Everyone knows that democracy is the worst system of government, except for all the others, which are even worster. <sic>
So, @radiolistener, if you think people are stupid to partake in democracy, what form of government do you advocate?
I too am interested in this. They have said what they don't like, I am keen to see them put their money where their mouth is and propose what system they would endorse.
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As I write above, radiolistener is my spokesperson and saying almost exactly what I am thinking but in a much more informed way.
What, about the voltmeter, or about democracy?
I hadn't gotten that far in the thread yet unfortunately and have disavowed them on the latter point in a post above.
I have spent all morning reading through this thread and I am not sure if I have gotten anything out of it. :-DD It has been entertaining at least.
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But even a voltmeter will not tell you if there is enough charge in the battery.
I'm going to pull this out from page one, as it seemingly got lost in the noise.
Battery voltage *alone* is not a reliable indicator of condition, nor state of charge. Lead acid chemistry is 'complex', especially as batteries age and/or when they are damaged. I've two 45Ah lead acid AGM batteries in my garage, less than a year old. They have never been 'abused' but they have been frequently cycled. Both show ~13v off load (measured at the terminals), and ~12.7v when initially connected to a 4A DC electronic load. When measured using said load, one returns a capacity of ~4Ah, the other 10Ah i.e. they are 'done'. Both were 'fully' charged prior to testing.
Equally, about 13.5 to 14v or so (some regulators have temperature compensation) when your engine is running tells you only that the alternator and voltage regulator are doing their job. It says nothing as to whether the battery is actually accepting charge, and even less about how much it can retain.
If you're really concerned about charge and discharge rates, I think you'd be better off looking at something like this: https://www.victronenergy.com/battery-monitors/smart-battery-shunt (https://www.victronenergy.com/battery-monitors/smart-battery-shunt)
The measurement of battery voltage is a fairly complicated thing, but there are some ways to simplify this.
For one, a single measurement at any time is probably not a good indicator of anything. However, a history of readings, especially under known conditions, is very good.
For a car battery, a good indicator is to measure the voltage while charging, but also to measure after the car engine is turned off, then also after the car has been sitting for a day or longer. If the voltage when the car is turned off is say 12.9v and the voltage after a day is 12.4v, it's probably doing ok, as long as that repeats to some degree day after day for a few weeks. If the car voltage is 12.9v and then after a day of sitting is 12.0v, that may mean the battery is either getting old or needs a good charge with a good charger. This is especially true if it goes below 12.0v after a day or maybe a few days.
If you let it sit for one day and see it go to a certain voltage, then watch for that behavior again and again. The point is to look for a change in behavior while measuring in the same way.
As above, there are two ways the battery voltage can get lower than usual. Either the battery is getting old, or the battery has been drained too low by sitting for too long. If it is old then there's no good way to help it except to charge it with a good charger and then keep checking it. If it is just drained too low, then charge it with a good charger and that could get it back to normal.
If the alternator is a good one, then just driving the car for a longer time could help charge the battery back to normal. That would be one that can put out maybe 14.8v to start. If it is an alternator that can only put out 14.0 volts, then a good charger will be needed to help get the battery back to normal.
These notes come after years of testing and monitoring the battery right in the car, and testing and monitoring using (for a long time) a solar charger system.
You clearly don’t know how car electronics work and their impact on a battery.
As if a battery with low voltage is by default defective.
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I also do not recommend keeping the meter connected to the battery. Use a switch if needed. That's because some panel meters do draw some significant current. Even a couple milliamps is not a good idea.
Can you explain what the problem is here?
What would happen if I connect it on the connection between starter battery and leisure batter, with dc-dc charger in between of course? Will the high amps of 40A+ blow the voltmeter? If so then why is it you can connect things direct to a battery and it doesn't blow in the same way?
Also if it is the case can I not regulate the offshoot circuit so that the voltmeter would no receive too much power? I am focusing on this just because, as mentioned, there are existing battery cable runs from the starter battery engine bay into the van habitation space, so it would be much simpler to tap into this somehow, if it can be done practically.
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Battery voltage *alone* is not a reliable indicator of condition, nor state of charge.
<SIGH>
Yes, yes, everybody knows this! The OP is not trying to ascertain the battery condition. He is trying to see whether it is being charged or not. A simple voltage measurement is entirely adequate for that purpose.
indeed.
its funny to see how some get lost in a non-discussion.
You mean, like the dozen or so pissing contest / ego clash posts that preceded it?
Heaven forbid someone add something actually germane to a discussion in the beginners section.
My remark wasn’t addressed to you.
Is yours to me?
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Can you explain what the problem is here?
What would happen if I connect it on the connection between starter battery and leisure batter, with dc-dc charger in between of course? Will the high amps of 40A+ blow the voltmeter? If so then why is it you can connect things direct to a battery and it doesn't blow in the same way?
You must be joking.,.
You really should start thinking less and doing more what some of us here are telling you.
Once again it seems you are completely off track/reality.
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I’ve remember several automotive electricians who relied on a voltmeter to check if the battery was charging properly and, as a result, drew incorrect conclusions and missed actual faults. If I recall correctly, there were even heated discussions on one automotive forum about why it happens. Measuring voltage at the cigarette lighter socket is even less reliable for this purpose.
For example, you might see the voltage at the cigarette lighter increase with engine on, yet both the alternator and the battery could be faulty - with the battery degraded as a result of the alternator failure. This is a real issue that occurs quite often in practice.
Some vehicle owners replace their batteries frequently (once a year), unaware that the root cause of early battery failure is often a faulty alternator.
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Secondary battery showing voltage and charge current from solar panel(s). Trickle charging of primary battery (that is never used when parked). Refrigeration box (high efficiency compressor) means fresh food even after many hot summer days out in "the sticks". Solar panels (2x50 W) mounted low between roof rails, no noise or drag. Bed & Breakfast for free wherever you want.
I know this is very OT so now you can go back to discussing tariffs, Agent Orange and politics.
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I’ve remember several automotive electricians who relied on a voltmeter to check if the battery was charging properly and, as a result, drew incorrect conclusions and missed actual faults. If I recall correctly, there were even heated discussions on one automotive forum about why it happens. Measuring voltage at the cigarette lighter socket is even less reliable for this purpose.
For example, you might see the voltage at the cigarette lighter increase with engine on, yet both the alternator and the battery could be faulty - with the battery degraded as a result of the alternator failure. This is a real issue that occurs quite often in practice.
Some vehicle owners replace their batteries frequently (once a year), unaware that the root cause of early battery failure is often a faulty alternator.
how many contradictions can you make in 1 sentence?
Voltage going up while alternator failed??
Please, don't talk about practice : you have none.
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how many contradictions can you make in 1 sentence?
Voltage going up while alternator failed??
Please, don't talk about practice : you have none.
There are zero contradictions in that sentence. If you don’t see this, I’d recommend reviewing basic physics and electrical principles theory before dismissing practical experience with comments like “you always wrong” or similar.
Yes, in many alternator/battery failure scenarios, you can still observe a voltage increase, especially if you measure voltage at some random electric network point of the vehicle instead of battery terminals. The mere fact that voltage rises cannot be taken as proof of a healthy alternator or battery. That’s precisely the point.
An alternator failure doesn’t necessarily mean it’s producing zero current, just as a battery failure doesn’t mean there’s no voltage at its terminals. If you don’t understand this, it suggests you lack sufficient experience with automotive electronics.
I apologize for the harsh tone, but I’m genuinely frustrated by amateurs presenting themselves as professional technicians and damaging vehicles due to their incompetence - I catch it several times in official service center, so I tend to respond to such behavior quite sharply. :-//
I’m not a professional automotive electric, but I often work with batteries in practice, as electronics is my field of interest and a personal hobby and I’ve repeatedly dealt with battery and wiring issues in vehicles, and had to study both the causes and practical repair methods to diagnose and resolve them myself. What you’re describing reminds me of my own early misconceptions, before I gained hands-on experience. Back then, I also didn’t consider where exactly voltage of the battery should be measured, nor was I aware of many potential issues. Simply because I wasn’t yet aware of the potential pitfalls involved and this is pretty usual for someone who don't have experience in the field. That’s why your simplistic reasoning leads me to believe you’re not a professional technician.
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yep always measure at battery terminals
had problems with bad contacts on relays, old cars with mechanicals on /off lights switches and others, because you may have carbon deposits, oxydation and other factors
now you have so many gadgets who do that, even cheap bluetooth ones ... they consume very little, and if your car runs at least once a week, no major battery drain occurs
a cigarette lighter can be useful, but not for real troubleshooting and battery drain problems, they can occur elsewhere
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how many contradictions can you make in 1 sentence?
Voltage going up while alternator failed??
Please, don't talk about practice : you have none.
There are zero contradictions in that sentence. If you don’t see this, I’d recommend reviewing basic physics and electrical principles theory before dismissing practical experience with comments like “you always wrong” or similar.
Yes, in many alternator/battery failure scenarios, you can still observe a voltage increase, especially if you measure voltage at some random electric network point of the vehicle instead of battery terminals. The mere fact that voltage rises cannot be taken as proof of a healthy alternator or battery. That’s precisely the point.
An alternator failure doesn’t necessarily mean it’s producing zero current, just as a battery failure doesn’t mean there’s no voltage at its terminals. If you don’t understand this, it suggests you lack sufficient experience with automotive electronics.
I apologize for the harsh tone, but I’m genuinely frustrated by amateurs presenting themselves as professional technicians and damaging vehicles due to their incompetence - I catch it several times in official service center, so I tend to respond to such behavior quite sharply. :-//
I’m not a professional automotive electric, but I often work with batteries in practice, as electronics is my field of interest and a personal hobby and I’ve repeatedly dealt with battery and wiring issues in vehicles, and had to study both the causes and practical repair methods to diagnose and resolve them myself. What you’re describing reminds me of my own early misconceptions, before I gained hands-on experience. Back then, I also didn’t consider where exactly voltage of the battery should be measured, nor was I aware of many potential issues. Simply because I wasn’t yet aware of the potential pitfalls involved and this is pretty usual for someone who don't have experience in the field. That’s why your simplistic reasoning leads me to believe you’re not a professional technician.
It’s obvious why specialized car centers and you are not compatible.
Just because it is a hobby of you , you pretend to know better than those ( engineers in electronics, not technicians as you like to call them) who work daily on cars with electrical issues and are trained by the best of manufacturers (like Bosch).
You lack the basics and like you said it yourself, you’re not a professional automotive electrician.
Your just pretentious.
Anyway: TS should know buy now what to do, although he doesn’t know the basic differences between voltage and current either so maybe he should consult a dealer.
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Measuring the voltage at the battery terminals is obviously the most accurate way to measure the battery voltage. Measuring the current in the battery lead is obviously the best way to check if the battery is being charged.
HOWEVER, what I and others are saying is that measuring the voltage at a convenient point, such as the cigarette lighter, definitely will allow the OP to determine whether a lower battery voltage is associated with the battery light coming on.
That is what the OP wanted to ascertain. It works. Voltage drops in the loom are too small to affect the binary result required.
Anybody who says this cannot be done and the only way to make the measurement is connecting directly across the battery terminals has obviously never worked on car electrics. I can tell when someone is speaking from theory or conjecture, rather than from practical experience. I'm almost certain that most of the contributors to this thread fall into the first category.
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My vehicle is much different from yours and I imagine much less reliable being almost 20 years older and already given the many electrical issues stated! So your case does not automatically transpose to mine.
I would disagree. Cigarette lighters are on high current circuits in all cases. Always have been, always will be.
Battery > main fuse box > accessory relay > cigarette lighter fuse > cigarette lighter socket.
The only difference with my first car, a 1966 Valiant, and today is that it skipped the accessory relay. Otherwise the wiring was the same. My 1977 Civic came without one, but I wired it in much like my 1966 Valiant utilizing a spare fuse location in the main fuse box.
Of course you are entirely welcome to make things harder on yourself and further mess up your wiring situation by adding direct connections to the battery terminals, ad-hock random fuses, a hole in your firewall, and unharnessed random wiring. I mean, what could go wrong?
I wonder why you asked the question in the first place, since you are soundly rejecting the consensus response.
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My vehicle is much different from yours and I imagine much less reliable being almost 20 years older and already given the many electrical issues stated! So your case does not automatically transpose to mine.
I would disagree. Cigarette lighters are on high current circuits in all cases. Always have been, always will be.
Battery > main fuse box > accessory relay > cigarette lighter fuse > cigarette lighter socket.
The only difference with my first car, a 1966 Valiant, and today is that it skipped the accessory relay. Otherwise the wiring was the same. My 1977 Civic came without one, but I wired it in much like my 1966 Valiant utilizing a spare fuse location in the main fuse box.
Of course you are entirely welcome to make things harder on yourself and further mess up your wiring situation by adding direct connections to the battery terminals, ad-hock random fuses, a hole in your firewall, and unharnessed random wiring. I mean, what could go wrong?
I wonder why you asked the question in the first place, since you are soundly rejecting the consensus response.
I’m happy with the free option to order a car without the cigar lighter. I don’t use it but instead you get a nice small box to put some coins in it. (Or your pills)
I wonder if all car brands give you that choice or if I was just lucky.
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Diagnosing a fault is a different problem than detecting a fault.
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I’m happy with the free option to order a car without the cigar lighter. I don’t use it but instead you get a nice small box to put some coins in it. (Or your pills)
I wonder if all car brands give you that choice or if I was just lucky.
The last 4 vehicles my wife and I bought here in Canada came with the "cigarette lighter" sockets, but they could not be used for cigarette lighters, just as accessory sockets. No ash trays either and no option to either have a real cigarette lighter or to eliminate the the socket. All these were either Hondas or Toyotas, so I'm not sure if other brands have different offerings. Smoking has been pretty well banned except out doors and in your own home since 2006 here in Ontario including public places, workplaces, restaurants, and their patios. No where that people can gather. There are all sorts of private bans too, like in some camping areas, motocross tracks, etc. You are not even allowed to smoke in your own car if you are carrying a baby or a non-smoker.
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It’s obvious why specialized car centers and you are not compatible.
Just because it is a hobby of you , you pretend to know better than those ( engineers in electronics, not technicians as you like to call them) who work daily on cars with electrical issues and are trained by the best of manufacturers (like Bosch).
You lack the basics and like you said it yourself, you’re not a professional automotive electrician.
Your just pretentious.
The problem with those technicians wasn’t that I lacked basic knowledge - it was that they were simply not competent enough in their work. Yes, they were used to dealing with customers who know nothing about electronics, allowing them to make mistakes, damage vehicles, charge for it, and still be thanked for their “help”. But unfortunately for them, in my case, they encountered a medical devices engineer, for whom electrical theory wasn’t a challenge and who was accustomed to much stricter quality standards and regulations, which made it easy to quickly identify their mistakes.
The same applies to this discussion. While I’m not a professional automotive electrician, I’ve dealt with issues you likely haven’t even encountered, either due to limited knowledge or rigid thinking. That’s why I immediately recognized that you’re not a practicing automotive professional. Because these are fairly common faults, and it’s hard to imagine that someone working professionally in automotive repair hasn’t encountered them and learned from experience to avoid such basic mistakes like you do. Yet, even after detailed clarifications, you still didn’t grasp the basic concepts. :-//
If you aim to become a professional technician, you should focus not on arguing but on analyzing potential fault causes and refining your diagnostic methods to avoid wasting time on ineffective procedures, such as measuring voltage at the cigarette lighter socket.
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That’s why I immediately recognized that you’re not a practicing automotive professional - because someone working with such systems daily would have understood the point instantly, without needing further explanations. Yet, even after detailed clarifications, you still didn’t grasp the basic concepts. :-//
Well, the difference between me and you is that I did work on car electronics after my engineering studies and this for well over 20 years at a Bosch car specialist and trained by Bosch at their headquarters as well training other dealerships at Bosch headquarters and as a consultant for BMW for specific electronic issues with the 850.
So I’m pretty sure I grasped the basic concepts…
As others said, you clearly have no experience whatsoever.
So, over and out.
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Well, the difference between me and you is that I did work on car electronics after my engineering studies and this for well over 20 years at a Bosch car specialist and trained by Bosch at their headquarters as well training other dealerships at Bosch headquarters and as a consultant for BMW for specific electronic issues with the 850.
So I’m pretty sure I grasped the basic concepts…
That’s another mistake on your part - trying to compare credentials instead of focusing on the technical discussion. In that case, you’ve lost again. Just FYI, I hold two engineering degrees - in electronics and in software development, one awarded with cum laude honors, and have worked in companies where certification, regulatory compliance, and regular audits were far stricter than anything you’ve likely experienced at Bosch. As for the companies themselves - they rank in the top 10 of Fortune 500 list. In addition, I’ve been passionate about radio electronics since childhood and hold amateur radio operator license. My hobby is developing SDR radios and DSP systems based on high-speed ADC/DAC and FPGA.
So, please don’t lecture me about professional engineering standards. Your recommendation to assess battery voltage by connecting to any random wire in the vehicle already says enough about your level of technical understanding. And your further arguments have only reinforced my conclusions. :-//
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A temporary voltmeter hook-up direct to the battery isn't too difficult in most vehicles, and can be done dirt cheap. Take some low current double-insulated flat twin mains flex, a couple of crimp ring terminals to fit your battery terminals, an inline fuseholder and a pair of 4mm banana plugs, and wire as previously described, leading the wire out from under the hood near the hinge, and in through the passenger door to a cheap DMM (preferably without auto-poweroff) in a cell-phone holder on the dash. Drill a couple of 4mm holes in a small block of wood or plastic to have something to 'safe' the plugs with if you disconnect the DMM. Do check where the cable is pinched by the hood and door frequently to make sure it isn't chafing.
If you want the convenience of a lighter socket voltmeter, it wont take long to see if it matches the DMM's reading of the voltage at the battery closely enough to be useful. Note that if a connection goes high resistance, a previously good lighter socket voltmeter may become significantly inaccurate *WITHOUT* *WARNING*, so its best *NOT* used for fault diagnosis but only for monitoring a known working charging system that is slightly inadequate, or monitoring how much 'juice' you've got left when off-grid. If it gives even slightly unexpected readings, you need to check the actual battery terminal voltage.
One of the things I keep in the electrical toolkit for any vehicle I am responsible for is a spool of hookup wire long enough to reach the length of the vehicle, with a 4mm plug on one end and a large alligator clip on the other. It is extremely valuable for tracking down mystery voltage drops in the wiring loom as it lets you easily do a binary search - first determining whether the drop is (mostly) in the positive or negative side, then tracing the affected side of the circuit in order of ease of access to localise the fault.
And for the record, last time I had a persistent battery warning light, I traced the problem to a couple of blown diodes in the alternator, and rebuilt it with a new diode plate* and changed the internal regulator to resolve it, testing the alternator on the bench charging a battery till I was certain it was reliably repaired, so I'm not *just* an armchair theorist!
* The diode plate was reasonably affordable vs individual press-fit diodes, which I didn't have the proper tooling to install + I had peace of mind that the other four diodes that had been significantly stressed were also being replaced. The regulator was more of a PITA as the original was discontinued and the replacement had a different pinout.
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. Your recommendation to assess battery voltage by connecting to any random wire in the vehicle already says enough about your level of technical understanding.
How many times do all of us have to explain this and what the issue of TS is?
You better went for a degree in reading.
And a second one in understanding :-DD
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How many times do all of us have to explain this and what the issue of TS is?
TS wants to check whether the battery is actually charging. Measuring voltage at the cig-lighter using a Chinese gadget is an even more stupid way for that than tesiting battery voltage through cig-lighter, even for a rough assessment.
As I’ve already explained earlier, the correct way to verify charging is to measure the charging current with a current clamp, ensuring that the current is within normal range and direction, and to monitor the voltage periodically directly at the battery terminals. This approach provides both accurate and meaningful results.
cig-lighter gadget cannot show you if battery is properly charging.
Voltage at the cigarette lighter can increase even when the battery is being charged incorrectly, due to faulty alternator or issues with connections and contact resistance within the vehicle’s wiring. Alternator faults are also a common problem - the alternator may still operate but supply incorrect charging current, which typically leads to premature failure of the battery, even if it’s new.
If you were a professional technician working in a service center, you would be well aware of this. Because such issue happens pretty often.
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How many times do all of us have to explain this and what the issue of TS is?
TS wants to check whether the battery is actually charging. Measuring voltage at the cig-lighter using a Chinese gadget is an even more stupid way for that than tesiting battery voltage through cig-lighter, even for a rough assessment.
As I’ve already explained earlier, the correct way to verify charging is to measure the charging current with a current clamp, ensuring that the current is within normal range and direction, and to monitor the voltage periodically directly at the battery terminals. This approach provides both accurate and meaningful results.
cig-lighter gadget cannot show you if battery is properly charging.
It seems you need a third degree:
Reread what we all wrote and tried to explain you.
We never talked about measuring current with a CT.
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It seems you need a third degree:
What I need or don’t need is something I’m fully capable of determining myself. I didn't asked your advice.
I have no need for advice from someone who recommends checking battery charging via the cigarette lighter socket. :-//
Reread what we all wrote and tried to explain you.
We never talked about measuring current with a CT.
Yes and that’s precisely the problem. You’ve been discussing how to determine whether the battery is properly charging with Chinese gadget through cig-lighter without mentioning the only reliable method - measuring the actual charging current. This clearly highlights the depth of misunderstanding. Without verifying actual current flow into the battery, any conclusions based solely on voltage readings are incomplete at best and misleading at worst, especially when you do it through cig-lighter. That’s exactly what I’ve been trying to explain to you.
What’s even more surprising is that you continue insisting on using the cigarette lighter for measurements, even after being repeatedly corrected in this discussion that voltage should be measured directly at the battery terminals, and charging should be verified by measuring current. This demonstrates a truly remarkable level of ignorance.
It might be a good idea to share a link to this discussion with your management.
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Those who really are involved in automotive electronics know how to determine if a battery is charging or not by measuring voltage anywhere and knowing how to interpret it.
You’re just not one of them.
Accept it.
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Those who really are involved in automotive electronics know how to determine if a battery is charging or not by measuring voltage anywhere and knowing how to interpret it.
Is that your personal opinion or the official position of Bosch?
Out of curiosity, we could escalate this question through an official inquiry to Bosch: does their diagnostic protocol really recommend assessing whether the battery is being properly charged by measuring voltage at the cigarette lighter, instead of using a current clamp near the battery terminal?
Which department you're worked for?
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You made it painfully clear you’re not able to accept others knowledge nor experience.
You even think you’re smarter than your own dealership.
They surely had a good time when you were trying to counter them.
Have fun explaining TS what and how to proceed.
:bullshit:
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You made it painfully clear you’re not able to accept others knowledge nor experience.
You even think you’re smarter than your own dealership.
They surely had a good time when you were trying to counter them.
Have fun explaining TS what and how to proceed.
:bullshit:
I did not ask for your opinion about my knowledge or your judgment of me. I posed a straightforward question: is it your personal opinion that verifying proper battery charging should be done by measuring voltage at the cigarette lighter instead of using current clamp meter near the battery terminal, or is this an official Bosch company protocol?
I’m starting to get the impression that you’re deliberately misleading people and damaging the company’s reputation by attributing such questionable practices to them. Fortunately, verifying this is simple - we can submit an official inquiry and see how Bosch responds on the matter. Let’s see then who’s actually writing bullshit.
I’m waiting for your confirmation: if you insist that this is truly Bosch’s official protocol, I will submit a formal inquiry to Bosch on this matter and share their response here. :popcorn: ;)
PS: By the way, it appears that I’ve previously contacted Bosch regarding a battery-related issue, so I already have their official contact information. :)
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This entire thread has been distorted, demolished and almost totally destroyed by one poster, @radiolistener.
I offer as a data point for evidence this reply (https://www.eevblog.com/forum/beginners/voltmeter-for-vehicle-battery-to-monitor-inside-of-cab/msg5977135/#msg5977135) earlier in the thread:
2023 Tacoma
Accessories on
Fan full blast
1) Engine off, at battery
2) Engine off, at lighter socket
3) Engine running, at battery
4) Engine running, at lighter socket
Maximum of about 1% voltage drop between battery and lighter socket.
I don't know about you, but I'd be quite happy with 1% accuracy.
Yeah, yeah; we can't be sure if this would be the case with your car. But it's easily ascertained by simple voltmeter tests at the battery and cig lighter socket.
Suggestion for the OP (with the understanding that this is free advice, which they are free to decline):
Do what the poster above did. Measure the voltage at both the battery and cig lighter socket.
If the cig-lighter socket reading is close enough to the battery reading for you, go ahead and use the lighter socket for voltage measurement.
If it's low for some reason, you could check the wiring between battery and lighter socket.
Just so you know, there's nothing that mysterious about car electrical wiring: all devices in the car are connected together to the 12-volt source (the battery). No in-line resistors or anything like that to drop the voltage.
Yes, yes: as @radiolistener has been obsessively pointing out, the best place to measure battery voltage is at the battery. However, that is a problematic way to measure it; as others have pointed out, if your meter draws any significant current and it's permanently connected to the battery, it can drain it over time. (Plus the problem of a much longer connection if you want the meter to be inside the car.)
Why don't you just get a meter that fits into the lighter socket and try it? It can't hurt anything, probably won't cost that much, and will be much better than the "idiot light" you have now.
Then you can report back to us how it worked.
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yep always measure at battery terminals
had problems with bad contacts on relays, old cars with mechanicals on /off lights switches and others, because you may have carbon deposits, oxydation and other factors
now you have so many gadgets who do that, even cheap bluetooth ones ... they consume very little, and if your car runs at least once a week, no major battery drain occurs
a cigarette lighter can be useful, but not for real troubleshooting and battery drain problems, they can occur elsewhere
Now we are getting some more support for team battery terminals! :-+
Could it be we aren't just fringe crazies after all like the 'majority' have made us out to be?
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Your just pretentious.
Lol you really lack the self-awareness to not see anything wrong with that accusation?
I tried to simply ignore your posts but this I could not ignore any more.
You spend most of your time belittling beginners on this subforum. You have a serious inferiority complex. You claim to be some world class engineer however you lack even basic social skills it is clear.
A guarantee you lack self-esteem in real life and this is the only place you can exert some little control to feel what you are unable to get in the real world.
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You claim to be some world class engineer however you lack even basic social skills it is clear.
You can’t be both ;D
But I’m old enough to know I’m not a world class engineer, on the contrary.
And I do have some decades of automotive experience as a job.
Anyway, good luck trying to find the culprit.
( it’s probably not even car related)
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A temporary voltmeter hook-up direct to the battery isn't too difficult in most vehicles, and can be done dirt cheap. Take some low current double-insulated flat twin mains flex, a couple of crimp ring terminals to fit your battery terminals, an inline fuseholder and a pair of 4mm banana plugs, and wire as previously described, leading the wire out from under the hood near the hinge, and in through the passenger door to a cheap DMM (preferably without auto-poweroff) in a cell-phone holder on the dash. Drill a couple of 4mm holes in a small block of wood or plastic to have something to 'safe' the plugs with if you disconnect the DMM. Do check where the cable is pinched by the hood and door frequently to make sure it isn't chafing.
If you want the convenience of a lighter socket voltmeter, it wont take long to see if it matches the DMM's reading of the voltage at the battery closely enough to be useful. Note that if a connection goes high resistance, a previously good lighter socket voltmeter may become significantly inaccurate *WITHOUT* *WARNING*, so its best *NOT* used for fault diagnosis but only for monitoring a known working charging system that is slightly inadequate, or monitoring how much 'juice' you've got left when off-grid. If it gives even slightly unexpected readings, you need to check the actual battery terminal voltage.
One of the things I keep in the electrical toolkit for any vehicle I am responsible for is a spool of hookup wire long enough to reach the length of the vehicle, with a 4mm plug on one end and a large alligator clip on the other. It is extremely valuable for tracking down mystery voltage drops in the wiring loom as it lets you easily do a binary search - first determining whether the drop is (mostly) in the positive or negative side, then tracing the affected side of the circuit in order of ease of access to localise the fault.
And for the record, last time I had a persistent battery warning light, I traced the problem to a couple of blown diodes in the alternator, and rebuilt it with a new diode plate* and changed the internal regulator to resolve it, testing the alternator on the bench charging a battery till I was certain it was reliably repaired, so I'm not *just* an armchair theorist!
* The diode plate was reasonably affordable vs individual press-fit diodes, which I didn't have the proper tooling to install + I had peace of mind that the other four diodes that had been significantly stressed were also being replaced. The regulator was more of a PITA as the original was discontinued and the replacement had a different pinout.
We have yet another one in favour of direct to terminals too. Is this good person an idiot too who doesn't know what they are talking about?
Soon we may even win a majority! 8)
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A temporary voltmeter hook-up direct to the battery isn't too difficult in most vehicles, and can be done dirt cheap. Take some low current double-insulated flat twin mains flex, a couple of crimp ring terminals to fit your battery terminals, an inline fuseholder and a pair of 4mm banana plugs, and wire as previously described, leading the wire out from under the hood near the hinge, and in through the passenger door to a cheap DMM (preferably without auto-poweroff) in a cell-phone holder on the dash. Drill a couple of 4mm holes in a small block of wood or plastic to have something to 'safe' the plugs with if you disconnect the DMM. Do check where the cable is pinched by the hood and door frequently to make sure it isn't chafing.
If you want the convenience of a lighter socket voltmeter, it wont take long to see if it matches the DMM's reading of the voltage at the battery closely enough to be useful. Note that if a connection goes high resistance, a previously good lighter socket voltmeter may become significantly inaccurate *WITHOUT* *WARNING*, so its best *NOT* used for fault diagnosis but only for monitoring a known working charging system that is slightly inadequate, or monitoring how much 'juice' you've got left when off-grid. If it gives even slightly unexpected readings, you need to check the actual battery terminal voltage.
One of the things I keep in the electrical toolkit for any vehicle I am responsible for is a spool of hookup wire long enough to reach the length of the vehicle, with a 4mm plug on one end and a large alligator clip on the other. It is extremely valuable for tracking down mystery voltage drops in the wiring loom as it lets you easily do a binary search - first determining whether the drop is (mostly) in the positive or negative side, then tracing the affected side of the circuit in order of ease of access to localise the fault.
And for the record, last time I had a persistent battery warning light, I traced the problem to a couple of blown diodes in the alternator, and rebuilt it with a new diode plate* and changed the internal regulator to resolve it, testing the alternator on the bench charging a battery till I was certain it was reliably repaired, so I'm not *just* an armchair theorist!
* The diode plate was reasonably affordable vs individual press-fit diodes, which I didn't have the proper tooling to install + I had peace of mind that the other four diodes that had been significantly stressed were also being replaced. The regulator was more of a PITA as the original was discontinued and the replacement had a different pinout.
We have yet another one in favour of direct to terminals too. Is this good person an idiot too who doesn't know what they are talking about?
Soon we may even win a majority! 8)
On the contrary ; you should read it again and accept there is a relation between the voltage reading and knowing if there is somehow an issue with either battery or the generator.
Those who are into automotives have that experience , that knowledge.
It seems you have forgotten your own question.
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Anyway, good luck trying to find the culprit.
Thank you for your kind wishes.
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Your just pretentious.
You spend most of your time belittling beginners on this subforum. You have a serious inferiority complex. You claim to be some world class engineer however you lack even basic social skills it is clear.
Um, is it possible that you missed something here? They were responding to @radiolistener (who is definitely not a beginner), not you.
I don't think anyone here has belittled you, have they?
BTW, what do you think about my suggestions above?
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Your just pretentious.
You spend most of your time belittling beginners on this subforum. You have a serious inferiority complex. You claim to be some world class engineer however you lack even basic social skills it is clear.
Um, is it possible that you missed something here? They were responding to @radiolistener (who is definitely not a beginner), not you.
I don't think anyone here has belittled you, have they?
Yes they have been condescending many times towards me in this post and others.
BTW, what do you think about my suggestions above?
Good suggestions, which is why I thanked you on that post. :-+
EDIT: Btw I give respect to the moderators in their hands off approach on this forum. They dropped in and despite the wild ride of shittalking they only commented gently to lay off the politics. :-DD If it was reddit the whole thing would have been locked at the first 'micro-aggression'.
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yep always measure at battery terminals
had problems with bad contacts on relays, old cars with mechanicals on /off lights switches and others, because you may have carbon deposits, oxydation and other factors
now you have so many gadgets who do that, even cheap bluetooth ones ... they consume very little, and if your car runs at least once a week, no major battery drain occurs
a cigarette lighter can be useful, but not for real troubleshooting and battery drain problems, they can occur elsewhere
Now we are getting some more support for team battery terminals! :-+
Could it be we aren't just fringe crazies after all like the 'majority' have made us out to be?
I don't even think there is 1% difference between the battery terminal and the cigarette lighter socket. The DMM has input impedance of 10MOhms how much resistance between the battery terminal and the lighter socket it has to be in order to drop 1%? About 100KOhms.
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This entire thread has been distorted, demolished and almost totally destroyed by one poster, @radiolistener.
Not at all. What’s really happening here is an attempt by some to promote dodgy technolgy methods or promote cig-lighter gadgets as the best way to check a battery. That would be one thing, but what’s truly surprising is their persistence in rejecting proper testing approaches and insisting on questionable dodgy methods instead.
Initially, there was pressure claiming that this is the crowd opinion, and now the assertion is that Bosch’s official protocol involves checking charging status via a voltmeter at the cigarette lighter. From my opinion not a smart approach :)
Maximum of about 1% voltage drop between battery and lighter socket.
The problem is that this “about 1%” applies only to a specific vehicle under specific conditions. In a different vehicle and different conditions, the voltage difference may be significantly different, and there’s no reliable way to predict exactly what it will be in your case and how it will vary over time.
Do what the poster above did. Measure the voltage at both the battery and cig lighter socket.
If the cig-lighter socket reading is close enough to the battery reading for you, go ahead and use the lighter socket for voltage measurement.
That approach can be used, but only with the understanding that the voltage difference you observed earlier can change at any time due to various factors like corrosion, vibration, etc. Therefore, relying on such measurements isn’t advisable - you should always verify directly at the battery terminals using a proper multimeter.
I use voltage readings from security system via a remote control unit in the same this way, periodically cross-checking them against direct measurements at the battery terminals. This allows me to monitor the voltage remotely. And with periodic check at the battery terminals I can see difference and observe its fluctuations of that difference over time. The difference is usually about ±0.1-0.2 V depending on some factors, probably temperature.
But note, while this method allows you to measure battery voltage and estimate its level of charge, it does not verify whether the battery is being properly charged. Generator components often fail - such as the regulator, windings, or belt, resulting in improper charging that can also quickly lead to fail the battery. Although a voltmeter can sometimes help detect this, it’s not straightforward and not easy. The simplest and most reliable method is to use a clamp meter like UT210 to measure the direction and magnitude of the current while the alternator is running, comparing these results with the battery’s charge level and alternator specification.
The most problematic situation is that a faulty alternator can damage a new battery, and conversely, a failing battery can cause alternator failure. Therefore, it’s important to check both components together.
I know of cases among acquaintances where they frequently replaced the battery without realizing the underlying issue was the alternator. There was even an instance where someone replaced the alternator but kept the old battery that had existing problems, which ultimately led to the failure of both the new alternator and the old battery.
Just so you know, there's nothing that mysterious about car electrical wiring: all devices in the car are connected together to the 12-volt source (the battery). No in-line resistors or anything like that to drop the voltage.
I would not agree, this information is not accurate. Automotive wiring is quite complex, even for experienced professional electricians. Every wire has inherent resistance, it’s not a superconductor, so there will always be some voltage drop depending on the current flowing through it. Moreover, modern vehicles have thousands of wires interconnected in complex network, making it quite challenging to trace and analyze voltage drops accurately, even for seasoned specialists.
The situation is further complicated by the fact that automotive wires and contacts are exposed to harsh environmental conditions and strong vibrations, which negatively affect contact reliability and increase resistance, including leakage currents through insulation damaged by vibration.
I am quite confident that even the most skilled wiring technician cannot instantly identify all connection details without consulting the technical documentation specific to that vehicle.
Yes, yes: as @radiolistener has been obsessively pointing out, the best place to measure battery voltage is at the battery. However, that is a problematic way to measure it; as others have pointed out, if your meter draws any significant current and it's permanently connected to the battery, it can drain it over time. (Plus the problem of a much longer connection if you want the meter to be inside the car.)
I disagree that this is problematic. It’s quite simple - just place a DMM in the trunk. You already need to open the hood periodically to check fluid and oil levels, so measuring voltage directly at the battery terminals is no more complicated.
If you have doubts about alternator and charging, get a clamp meter like the UT210, diagnostics will take only a couple of minutes. There’s no need to connect any dodgy technology gadgets that would constantly and unnecessarily drain the battery.
I perform this check regularly and have no need for additional gadgets.
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This entire thread has been distorted, demolished and almost totally destroyed by one poster, @radiolistener.
Not at all. What’s really happening here is an attempt by some to promote dodgy technolgy methods or promote cig-lighter gadgets as the best way to check a battery.
No.
That's your misrepresentation of the issue here.
Nobody has said, nor would they say, that using the lighter socket is the best way to check a battery. Nobody.
What we're saying is that in most cases, absent any significant wiring deficiencies, checking the battery voltage at the lighter socket is good enough for most purposes (and evidently for the OP's purposes, which is the important thing here, as we're dealing with their question). As in within 1%.
You're the one with the anal fixation on only ever using a test directly at the battery terminals as acceptable.
It's up to the OP now. If they follow my (and others') suggestions, they'll do some measurements of their own; if they're really curious they can test both at the battery terminals and at the lighter socket. If the latter is within 1% of the former, then Bob's your uncle, as they say.
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You made it painfully clear you’re not able to accept others knowledge nor experience.
You even think you’re smarter than your own dealership.
They surely had a good time when you were trying to counter them.
Have fun explaining TS what and how to proceed.
:bullshit:
I did not ask for your opinion about my knowledge or your judgment of me. I posed a straightforward question: is it your personal opinion that verifying proper battery charging should be done by measuring voltage at the cigarette lighter instead of using current clamp meter near the battery terminal, or is this an official Bosch company protocol?
I’m starting to get the impression that you’re deliberately misleading people and damaging the company’s reputation by attributing such questionable practices to them. Fortunately, verifying this is simple - we can submit an official inquiry and see how Bosch responds on the matter. Let’s see then who’s actually writing bullshit.
I’m waiting for your confirmation: if you insist that this is truly Bosch’s official protocol, I will submit a formal inquiry to Bosch on this matter and share their response here. :popcorn: ;)
PS: By the way, it appears that I’ve previously contacted Bosch regarding a battery-related issue, so I already have their official contact information. :)
Then just contact Bosch instead of using it as a threat that you are right, maybe while you wait for the answer you will stop derailing the thread!
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No.
That's your misrepresentation of the issue here.
Nobody has said, nor would they say, that using the lighter socket is the best way to check a battery. Nobody.
No, there is no misrepresentation, I'm talking about these claims:
I knew someone would bring this up, but I think it only complicates things. He just needs some idea of if and when the battery is being charged. That's why I suggested the cigarette lighter socket. It will be more than sufficient to do the job.
I have been analyzing car electronics and car battery issues for more than 20 years.
You can reliably measure the battery voltage at any point in the car.
And try to understand why I’m telling its better to measure somewhere down the road instead of next to the battery.
It seems I have to explain some basics too.
Reviewing the discussion from the beginning, I am increasingly convinced that all these claims about measuring through the cigarette lighter are part of a coordinated marketing campaign by trolls, apparently aimed at promoting questionable gadgets designed for the cigarette lighter socket. :)
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No.
That's your misrepresentation of the issue here.
Nobody has said, nor would they say, that using the lighter socket is the best way to check a battery. Nobody.
No, there is no misrepresentation, I'm talking about these claims:
I knew someone would bring this up, but I think it only complicates things. He just needs some idea of if and when the battery is being charged. That's why I suggested the cigarette lighter socket. It will be more than sufficient to do the job.
"More than sufficient" ≠ "better".
So far as those other two go, they were saying that it's better to measure at the lighter socket not because it's more accurate but because it's more practical to the OP's purpose and would be accurate enough.
You seem to completely lack an understanding of the concept "accurate enough for my purposes".
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Then just contact Bosch instead of using it as a threat that you are right, maybe while you wait for the answer you will stop derailing the thread!
Yes, I intend to contact Bosch, but first I would appreciate clarification on whether the claim about measuring via the cigarette lighter reflects Sorama’s personal opinion, which may not align with Bosch’s official protocol, or if it is indeed a practice genuinely followed by Bosch engineers. The scope and nature of my inquiry will depend on this distinction.
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the cigarette lighter is is rated for 10-15A, if it doesn't show battery voltage something else is seriously wrong
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"More than sufficient" ≠ "better".
So far as those other two go, they were saying that it's better to measure at the lighter socket not because it's more accurate but because it's more practical to the OP's purpose and would be accurate enough.
You seem to completely lack an understanding of the concept "accurate enough for my purposes".
The phrase "accurate enough" applies only when the chosen measurement method is technically appropriate for the diagnostic goal. In this case, the TS asked how to verify whether the battery is being charged correctly - not merely whether some voltage is present in the system or whether the alternator activation causes a shift in potential distribution across the vehicle’s wiring.
Voltage measurements alone, particularly at auxiliary points such as the cigarette lighter socket, cannot provide reliable or meaningful information about the charging process. Without direct assessment of the actual charging current flowing into the battery, voltage readings are insufficient and potentially misleading when evaluating charging quality.
Presenting such indirect measurements as "sufficient" risks misinforming users and promoting incorrect diagnostic practices.
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Not at all. What’s really happening here is an attempt by some to promote dodgy technolgy methods or promote cig-lighter gadgets as the best way to check a battery.
Hey, wait, wait! Nobody said it was the best way! I, and others, have said it's a perfectly adequate way - and probably the easiest - to check for a correlation between a lower battery voltage and the battery light coming on.
I stand by that.
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The phrase "accurate enough" applies only when the chosen measurement method is technically appropriate for the diagnostic goal. In this case, the TS asked how to verify whether the battery is being charged correctly - not merely whether some voltage is present in the system or whether the alternator activation causes a shift in potential distribution across the vehicle’s wiring.
Voltage measurements alone, particularly at auxiliary points such as the cigarette lighter socket, cannot provide reliable or meaningful information about the charging process. Without direct assessment of the actual charging current flowing into the battery, voltage readings are insufficient and potentially misleading when evaluating charging quality.
Presenting such indirect measurements as "sufficient" risks misinforming users and promoting incorrect diagnostic practices.
Good grief! :palm:
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The phrase "accurate enough" applies only when the chosen measurement method is technically appropriate for the diagnostic goal. In this case, the TS asked how to verify whether the battery is being charged correctly - not merely whether some voltage is present in the system or whether the alternator activation causes a shift in potential distribution across the vehicle’s wiring.
Voltage measurements alone, particularly at auxiliary points such as the cigarette lighter socket, cannot provide reliable or meaningful information about the charging process. Without direct assessment of the actual charging current flowing into the battery, voltage readings are insufficient and potentially misleading when evaluating charging quality.
Presenting such indirect measurements as "sufficient" risks misinforming users and promoting incorrect diagnostic practices.
Good grief! :palm:
Obviously he'd only be satisfied with a dedicated, permanently-installed voltage monitor (7.5 DMM?) and a shunt in line with the battery to measure current, accurate to 0.01%.
Something the OP never remotely asked for, BTW.
Talk about missing the point ...
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the cigarette lighter is is rated for 10-15A, if it doesn't show battery voltage something else is seriously wrong
If you're specifically interested in measuring the battery voltage itself, even mentioned 1-2% error means approximately 0.25V at 12.7V, which translates to about a 25% error in estimating the battery level of charge - quite significant. When you know average difference with real battery voltage you can live with it depending on your "accurate enough" interpretation.
However, this isn’t the main issue here. The TS asked how to verify whether the battery is charging correctly, meaning whether the alternator and its regulator are functioning properly - not how to check the level of charge. And that cannot be determined either through the cigarette lighter socket or even by measuring voltage directly at the battery terminals. Proper charging assessment requires monitoring the actual charging current flowing into the battery. It requires current clamp meter.
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Obviously he'd only be satisfied with a dedicated, permanently-installed voltage monitor (7.5 DMM?) and a shunt in line with the battery to measure current, accurate to 0.01%.
Something the OP never remotely asked for, BTW.
Talk about missing the point ...
Please don’t project your assumptions onto me. As I’ve explained multiple times, for alternator diagnostics I use a simple UT210 clamp meter, which is more than sufficient and takes just a couple of minutes. It can measure voltage either. For monitoring battery charge level, even a basic DT830 multimeter with 3 digits fully meets my needs.
So kindly stop attributing to me false demands I never made.
PS: That said, I do own a 6.5-digit DMM either and occasionally use it for automotive measurements. In fact, when charging a car battery, I usually monitor the voltage using my 6.5-digit DMM, not for the sake of precision, but simply because it’s positioned right next to the power supply I use for charging. I see nothing wrong with using higher-grade equipment. :)
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Obviously he'd only be satisfied with a dedicated, permanently-installed voltage monitor (7.5 DMM?) and a shunt in line with the battery to measure current, accurate to 0.01%.
Something the OP never remotely asked for, BTW.
Talk about missing the point ...
So kindly stop attributing to me false demands I never made.
It was, it was a, a, it was a joke, son.
Apparently your irony detector is badly in need of recalibration.
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There’s one important consideration when checking the alternator using the UT210 - starter current exceeds its measurement range, so it’s important to remove the clamp from the cable during engine start to avoid clamp meter damage. But as a plus it works very well for measuring standby current with the engine off and all consumers switched off.
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I disagree that this is problematic. It’s quite simple - just place a DMM in the trunk. You already need to open the hood periodically to check fluid and oil levels, so measuring voltage directly at the battery terminals is no more complicated.
If this is your main reasoning then you actually have totally missed the point of the OP!
The whole thing is about doing it conveniently in real time. I stated I have already done it several times by popping the hood and now don't want to do that any more and rather have a more convenient way to monitor it on the fly, while driving.
If the cigarette port method will do that, albeit at a little less accuracy, then I am with those guys. It is not about extreme accuracy, just to know that the alternator is working and charging so then I can feel I can not pay attention to the battery light being on when it does decide to illuminate.
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This entire thread has been distorted, demolished and almost totally destroyed by one poster, @radiolistener.
Not at all. What’s really happening here is an attempt by some to promote dodgy technolgy methods or promote cig-lighter gadgets as the best way to check a battery.
No.
That's your misrepresentation of the issue here.
Nobody has said, nor would they say, that using the lighter socket is the best way to check a battery. Nobody.
What we're saying is that in most cases, absent any significant wiring deficiencies, checking the battery voltage at the lighter socket is good enough for most purposes (and evidently for the OP's purposes, which is the important thing here, as we're dealing with their question). As in within 1%.
You're the one with the anal fixation on only ever using a test directly at the battery terminals as acceptable.
It's up to the OP now. If they follow my (and others') suggestions, they'll do some measurements of their own; if they're really curious they can test both at the battery terminals and at the lighter socket. If the latter is within 1% of the former, then Bob's your uncle, as they say.
As per my post above, I believe I may have broken out of the radiolistener spell now when I read their reply that they had no consideration for convenience in this, which is the whole point of my post!
I think in that case their name might better be radiosilence as they have not listened to anything I was saying in hammering only at the terminals point. ;D
If the cigarette lighter socket is good enough for the task I actually want it for, which is only to give a gross indication of voltage spiking to indicate that the alternator is charging, then I agree they have wasted everyone's time arguing about something that is absolutely besides the point.
I am not experienced enough to know one way or the other whether their point is salient or not as to whether the cig socket is too inaccurate to be useful but I leave that to you guys to slug it out. :D
As you mention though, Analog Kid, I can test myself with my DMM. I apologize for ignoring your patient advice but please cut me some slack as I was in a cult and could not see outside of it for that time.
Getting back to actual practical matters which may help my situation then...I have since gone and bought a cheap digital meter which only has the bare wires. As such how could you guys advise I connect it up now, considering it has not cigarette port socket? Buying a socket would probably make it cost as much as a ready made one. If you are all saying that it doesn't matter where on the vehicle electrical system it goes, is there some other place I could wire it up without having to run cables out anywhere and it was mentioned earlier that wiring to my dc-dc charger with 40A would be a no go. :D
EDIT: Actually probably better to just buy a cigarrette insert as I guess only a couple of pounds and probably easier than rummaging around looking for wires to piggy back to and still cheaper. I have bought the little voltmeter now so might as well make use of that and make my own one for the cig port.
I agree now the thread was hideously derailed by radiolistener. :-DD
Ok I am doing some research and just reading the wiki on the DC power plug the answer was revealed to me right in this sentence!:
The voltage of the power outlet is usually near 12 V DC, and may be elevated between 13.5 V to 15 V while the engine is running. On trucks, the voltage of the power outlet may be near 24 V DC.
https://en.wikipedia.org/wiki/Automobile_auxiliary_power_outlet
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Can someone explain to me why I can't add another wire on the dc-dc charger line? It was told 'no' without explanation.
Yes there will be 40A amps but can't I somehow make another circuit on that line and limit the amps going through just the side circuit? Is it simple or not to do that? Btw I was told by the charger manufacturer when fault finding that I shouldn't be worried about putting the DMM on the positive and negative while it is running as it won't cause the current to go through it so why would it be different in this case?
As I want to use it for the foreseeable future I don't want the 12v plug always in use so I couldn't plug in other things, preferably. So I would prefer it had its own dedicated circuit.
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You can. As long as you are careful routing said wire past metal edges there are no reasons except possibly cosmetic not to. Depending on the meter you attach you might want to put some sort of voltage clamp to protect it from the sometimes surprisingly large voltage spikes which can occur in auto electric systems. Not likely to be a huge problem, but.something to think about.
As has been pointed out endlessly in this thread, it won't be a perfect diagnostic. How you use the information is up to you. I believe that it will provide useful information, though it will require some thought.
Many people agree, it is why a voltmeter is built into the dash instrumentation of a huge number of vehicles. The reason it is omitted from many others is cost savings, cosmetic reasons, and possibly a belief that the information won't be of use to the target purchaser of their vehicles. Tachometers are another example of such an instrument.
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You can. As long as you are careful routing said wire past metal edges there are no reasons except possibly cosmetic not to.
Will it only take the amps it wants then and the whole 40+ when the charger is running won't go to it?
EDIT: Hmm as I think about it, if we forget about the cable run, it is the equivalent to having both plugged right into the starter battery terminals isn't it? So whether both are wired direct at the terminal or at the end of a long run of wire, it is the same right? So it should be the same case that the voltmeter would not pull more amps when the dc-dc charger is running, than if it were also connected at the battery terminal posts itself. Is that right?
Can you explain what being careful about routing past metal edges means in this context? Is it anything different from normal circuits of not having exposed wires touching metal? If the worst happened and they did touch what would happen? Won't the ground to the metal chasis make it safe? Not that I intend for it, just to know the safety parameters.
I already have this (https://www.12voltplanet.co.uk/marine-battery-isolator-switch-with-removable-actuator-2-positions-200a-continuous.html) battery isolator switch in place between the start battery positive and dc-dc charger positive input so I can disable it when I don't want it in use. I was thinking I could just connect the positive for the voltmeter to the positive terminal on the starter battery side there. Would that work?
In this case I would not be making any kind of junctions or routing and just adding the little voltmeter wire to that existing terminal which would be a safe bet right?
Then just run the negative to the common negative busbar for the leisure battery.
Can you explain to me, if this is ok, why the amps would not burst into the voltmeter too when the charger is running?
Depending on the meter you attach you might want to put some sort of voltage clamp to protect it from the sometimes surprisingly large voltage spikes which can occur in auto electric systems. Not likely to be a huge problem, but.something to think about.
It is just this (https://www.switchelectronics.co.uk/products/blue-led-digital-voltmeter-4-5-30v) little thing.
As has been pointed out endlessly in this thread, it won't be a perfect diagnostic. How you use the information is up to you. I believe that it will provide useful information, though it will require some thought.
Yes we don't have to waste any more time on that. :-DD Good enough for the purpose of giving a rough idea of if the alternator is working when the engine is running.
Many people agree, it is why a voltmeter is built into the dash instrumentation of a huge number of vehicles. The reason it is omitted from many others is cost savings, cosmetic reasons, and possibly a belief that the information won't be of use to the target purchaser of their vehicles. Tachometers are another example of such an instrument.
Well that is a debate which is besides the point here. Most consumers I don't think care a hoot about looking at that stuff. It is more an enthusiasts thing or when there is a specific reason for knowing on a real-time basis, like in my case with the intermittent battery light. I would not even think about it if the battery light has not started this behavior and I imagine most normal road users are the same. If it is not a problem they won't care.
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just plug the damn voltmeter into the cig socket and then take it from there! It's got it's own fused spur from the distribution board so is almost as good as putting it on the battery. The charge current to the battery is low as the alternator runs the electrics when the engine is running so minimal voltage drop back to the terminals. What on earth is all the fuss about? we are not trying to split the atom.
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yep always measure at battery terminals
had problems with bad contacts on relays, old cars with mechanicals on /off lights switches and others, because you may have carbon deposits, oxydation and other factors
now you have so many gadgets who do that, even cheap bluetooth ones ... they consume very little, and if your car runs at least once a week, no major battery drain occurs
a cigarette lighter can be useful, but not for real troubleshooting and battery drain problems, they can occur elsewhere
Now we are getting some more support for team battery terminals! :-+
Could it be we aren't just fringe crazies after all like the 'majority' have made us out to be?
I don't even think there is 1% difference between the battery terminal and the cigarette lighter socket. The DMM has input impedance of 10MOhms how much resistance between the battery terminal and the lighter socket it has to be in order to drop 1%? About 100KOhms.
I don't think you are reading all the replies such as post #83.
The difference in voltage between the battery terminals and the cigar lighter socket does NOT depend on the current draw of the voltmeter when the voltmeter draws an insignificant current like 1ma but even 10ma. It's the other devices in the car that make a difference because some of them draw a lot of current like 10 amps or more. That causes a drop in the wiring which the voltmeter could pick up as a lower voltage.
You could try measuring the battery voltage and the cigar lighter voltage and turn the headlights on to see if that makes any difference. Depending on the wiring under the hood, it may or may not affect the readings. Some cars will be affected a lot more than others. That's why people recommend measuring at the battery terminals which is always accurate.
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just plug the damn voltmeter into the cig socket and then take it from there! It's got it's own fused spur from the distribution board so is almost as good as putting it on the battery. The charge current to the battery is low as the alternator runs the electrics when the engine is running so minimal voltage drop back to the terminals. What on earth is all the fuss about? we are not trying to split the atom.
That's what I do too even though I know better. It's because I have a history of what the readings should be so I always have something to compare new readings to.
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I know better as well, but it's a first step. If the voltage is about right then the alternator is working. If it's low then investigate further with a more inconvenient but more accurate method.
If the best way is the hard way and something that will give some good pointers while not definitive is easy then start with the easy. 7 pages, ok including a load of political crap.
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The whole thing is about doing it conveniently in real time. I stated I have already done it several times by popping the hood and now don't want to do that any more and rather have a more convenient way to monitor it on the fly, while driving.
Real-time monitoring while driving isn’t practically necessary. Using a simple multimeter and clamp meter, you can fully diagnose both the battery and alternator in 5-10 minutes: check the charge level, confirm the presence and check strength of charging current, perform load testing, and assess internal resistance - all of which provide a clear picture of battery health and charging performance.
If you really want live readings while driving, you could install voltage and current sensors directly at the battery terminals and run wires into the cabin. But these readings won’t offer much practical value during driving and will only distract you. Real diagnostics should be performed while stationary. In practice, real-time monitoring makes sense only as a visual gimmick for dashboard display, not as a meaningful diagnostic tool.
If the cigarette port method will do that, albeit at a little less accuracy, then I am with those guys. It is not about extreme accuracy, just to know that the alternator is working and charging so then I can feel I can not pay attention to the battery light being on when it does decide to illuminate.
You’ve been misled - a voltmeter in the cigarette lighter cannot indicate whether your charging system is functioning correctly. Even for basic voltage monitoring, this method is highly unreliable (especially with Chinese gadgets) and should not be considered a proper diagnostic tool.
Of course, you can install a voltmeter in the lighter socket and enjoy watching its display shining, but relying on those readings for assessing your alternator or battery condition is a mistake. That’s why I don’t use such gadgets at all, recognizing their practical uselessness.
I do monitor system voltage via my remote alarm control, but only as a convenience to remotely observe battery status during long idle periods. I don’t trust those readings and periodically perform proper diagnostics directly at the battery using accurate instruments.
Also keep in mind: if your vehicle’s cigarette lighter remains powered when the ignition is off, you risk forgetting to remove the device, which can completely drain the battery. Deep discharge is harmful to automotive batteries and often leads to permanent damage, requiring replacement.
Good enough for the purpose of giving a rough idea of if the alternator is working when the engine is running.
No, no and no! Absolutely not good enough!
Voltage measurement alone cannot confirm that your alternator is functioning correctly, even if you measure it directly on the battery terminals. I’ve personally seen experienced auto electricians overlook charging system faults (failed alternator) by relying solely on voltage readings, unable to understand why the battery kept failing prematurely. And this isn’t an single mistake - many experienced auto electricians fall into this trap. Not to mention ordinary users, for whom this risk is even higher.
Alternator failure doesn’t necessarily mean it stops generating power or affecting the vehicle’s system voltage.
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:horse:
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No, no and no! Absolutely not good enough!
^^^^ Heels dug in. ^^^^
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with a modern car can get much more complicated, the voltage can be all over the place because the ECU controls the alternator to only charge there is high consumption, medium engine load, overrun, not too hot, SOC low, etc. etc.
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just plug the damn voltmeter into the cig socket and then take it from there! It's got it's own fused spur from the distribution board so is almost as good as putting it on the battery. The charge current to the battery is low as the alternator runs the electrics when the engine is running so minimal voltage drop back to the terminals. What on earth is all the fuss about? we are not trying to split the atom.
This has nothing to do with what I am asking though. I guess you have only skimmed bits of the thread.
I already know what is going on by having checked at the terminals (the holy grail :-DD) many times over different periods.
The whole purpose of the post is to have something installed to be on all the time when driving to monitor while driving.
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:horse:
You did not answer the direct question.
Is it your personal opinion that verifying proper battery charging should be done by measuring voltage at the cigarette lighter instead of using a current clamp near the battery terminal? Or is this an official Bosch diagnostic protocol?
Please clarify explicitly, without evasions.
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The whole thing is about doing it conveniently in real time. I stated I have already done it several times by popping the hood and now don't want to do that any more and rather have a more convenient way to monitor it on the fly, while driving.
Real-time monitoring while driving isn’t practically necessary. Using a simple multimeter and clamp meter, you can fully diagnose both the battery and alternator in 5-10 minutes: check the charge level, confirm the presence and check strength of charging current, perform load testing, and assess internal resistance - all of which provide a clear picture of battery health and charging performance.
This makes me see you haven't grasped through the whole thread why I want this.
Others who have followed my previous posts about the intermittent battery light issue will understand, I hope.
I am not concerned whether the alternator is working or not at this time. I want to install this to be able to make sure I can check whenever I am driving that it is continuing to do so, over time. It is not about diagnosing a current problem with it but rather to keep an eye on the voltage in case it ever should but rather to know that it continues to be working.
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The whole purpose of the post is to have something installed to be on all the time when driving to monitor while driving.
So what are you still arguing about? go and put your cigarette lighter voltmeter in and be done with it. If you don't like that then you need to work out how to get cables from the battery to the cab. You can then test the voltage any time you fancy and if you install a shunt with amplifier and send a reading back to the cab you can see that too. What is 7 pages about?
Of course I have skim read, I keep getting reports about this ridiculous thread! Soon I will just close it!
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The whole purpose of the post is to have something installed to be on all the time when driving to monitor while driving.
So what are you still arguing about? go and put your cigarette lighter voltmeter in and be done with it. If you don't like that then you need to work out how to get cables from the battery to the cab. You can then test the voltage any time you fancy and if you install a shunt with amplifier and send a reading back to the cab you can see that too. What is 7 pages about?
Of course I have skim read, I keep getting reports about this ridiculous thread! Soon I will just close it!
I also already covered that. I don't want the cig port to be occupied all the time as I want it free for other stuff and I want the voltmeter working all the time when driving so have its own circuit.
It is a shame if you close it because it is not my fault that it got destroyed with politics and dick measuring BS and I still want to work out how best to wire it which is a strictly practical matter and the only reason I made the post in the beginning!
I had the idea from the start to use a dedicated connection and that is why I was not interested in the 12v port suggestion for the reason stated above.
Not sure what you mean by arguing. I am merely trying to get my point across of what I was trying to ask from the beginning while others added on what I should be doing instead and that is where the 'arguments' come from. 12v port is simply not suitable for my use case and I want to know how best to wire up a dedicated circuit which is all I have ever been asking which got lost in the sea of other opinions.
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This has nothing to do with what I am asking though. I guess you have only skimmed bits of the thread.
I already know what is going on by having checked at the terminals (the holy grail :-DD) many times over different periods.
The whole purpose of the post is to have something installed to be on all the time when driving to monitor while driving.
Your question has already been answered regarding how to properly verify alternator performance and battery charging - there’s no point repeating the same explanations.
Regarding continuous monitoring while driving: such readings will be practically useless and will only serve as a distraction, which can be dangerous when driving.
If you simply wish to see some random numbers while on the move - you can connect a voltmeter to the cigarette lighter or run wires directly from the battery. But in both cases, the data you’ll get will have little real diagnostic value, its just useless.
For actual diagnostics, you still need to open the hood, check oil and fluid levels, measure voltage directly at the battery terminals, and check the actual charging current if you want to assess alternator performance correctly.
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No, no and no! Absolutely not good enough!
Back in the good 'owd days, cars came with an ammeter which showed whether current was flowing into or out of the battery.
Then one day alternators became too powerful - it wasn't practical to pipe 100A or more to the dashboard to operate an ammeter. So ammeters were dropped and for at least a couple of decades cars came with a voltmeter on the dashboard instead.
The voltmeter was usually marked with coloured bands, and the idea was that if the voltmeter was in the green band you could assume the battery and charging system were working OK. If not, then there was a problem.
Voltmeters only disappeared with the more recent trend to do away with gauges and instead use warning lights and written fault descriptions (for example, my car has neither type of meter nor even a warning light, but it says "CHECK ALTERNATOR" on the information screen) .
But for a long time, voltmeters were provided as a means of the driver monitoring the health of the battery and charging system. Of course it wasn't perfect, but the industry and most of the users considered it to be useful enough to include one. Articles were written in motoring magazines about how to interpret the voltmeter.
I can tell you this (and I've just checked with a retired car technician from that era): not a single one of those voltmeters had its own pair of wires going all the way back to the battery terminals.
I feel sorry for @radiolistener because he's got himself into an unfortunate position which he cannot back out of (let's be honest, we've all been there), but he is of course right in theory when he says a voltmeter cannot alone provide a complete analysis of the battery condition and charging system function. But in practice it can provide a very helpful - and usually sufficient - indication that something is amiss.
That is all the OP needs at this juncture: is the warning light associated with a drop in battery voltage (which usually implies a drop in charging current)? And a way of monitoring this as he is driving around. More detailed analysis might be required later, but for now a voltmeter will do the job.
@radiolistener's position is contrary to standard practice across the car industry for a good two decades or so. The suggestion to plug in a voltmeter has extensive precedent.
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:horse:
You did not answer the direct question.
Is it your personal opinion that verifying proper battery charging should be done by measuring voltage at the cigarette lighter instead of using a current clamp near the battery terminal? Or is this an official Bosch diagnostic protocol?
Please clarify explicitly, without evasions.
No, of course not.
Proper testing of a battery is done with a specific charger/tester on the battery (without connection to the car).
I have never ever said or even mentioned that a battery can be fully tested by using a dmm connected on the cigarette lighter.
What I did say - at least tried to say- is that when measuring the voltage anywhere, and with experience and knowledge of how car electricity is generated, one can determine if there is somehow an issue with the battery or the charging system.
That is what TS can do (and honestly, I think the only thing he could or should do).
Of course you can measure the current with a clamp and we did that also when there was an indication of an issue somewhere in the car regarding the voltage.
You can also take the battery apart and refill it and log its behavior but that are not things a normal person would or should do.
Its like escalating a ticket to a support team: first it goes to first level, if they cannot solve it or think it is not up to them, them put in in the queue for second level and they possibly forward it to third level.
The same goes for any problem with a car (although with less support levels).
If we got a car with strange behavior, that car already passed the local dealer and probably some other technicians, with or without proper knowledge.
Radiolistener is putting words in my mouth, while all I tried to tell, with respect to TS, is that measuring the voltage anyhow and anywhere will give you (or experienced automotive technicians), already a clue of what is going on.
Like things that should be checked or can already be ruled out.
consider it as a first level support.
But we never send a battery to Varta (which is the manufacturer of the Bosch batteries) for testing in a lab.
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No, no and no! Absolutely not good enough!
Back in the good 'owd days, cars came with an ammeter which showed whether current was flowing into or out of the battery.
Then one day alternators became too powerful - it wasn't practical to pipe 100A or more to the dashboard to operate an ammeter. So ammeters were dropped and for at least a couple of decades cars came with a voltmeter on the dashboard instead.
The voltmeter was usually marked with coloured bands, and the idea was that if the voltmeter was in the green band you could assume the battery and charging system were working OK. If not, then there was a problem.
Voltmeters only disappeared with the more recent trend to do away with gauges and instead use warning lights and written fault descriptions (for example, my car has neither type of meter nor even a warning light, but it says "CHECK ALTERNATOR" on the information screen) .
But for a long time, voltmeters were provided as a means of the driver monitoring the health of the battery and charging system. Of course it wasn't perfect, but the industry and most of the users considered it to be useful enough to include one. Articles were written in motoring magazines about how to interpret the voltmeter.
I can tell you this (and I've just checked with a retired car technician from that era): not a single one of those voltmeters had its own pair of wires going all the way back to the battery terminals.
I feel sorry for @radiolistener because he's got himself into an unfortunate position which he cannot back out of (let's be honest, we've all been there), but he is of course right in theory when he says a voltmeter cannot alone provide a complete analysis of the battery condition and charging system function. But in practice it can provide a very helpful - and usually sufficient - indication that something is amiss.
That is all the OP needs at this juncture: is the warning light associated with a drop in battery voltage (which usually implies a drop in charging current)? And a way of monitoring this as he is driving around. More detailed analysis might be required later, but for now a voltmeter will do the job.
@radiolistener's position is contrary to standard practice across the car industry for a good two decades or so. The suggestion to plug in a voltmeter has extensive precedent.
That is interesting background information but does not address what I am asking - how to wire it if I don't want to use the 12v port.
I asked earlier, can I wire it to the existing wires running from the starter battery into the van's dc-dc charger circuit to which CatalinaWOW noted that yes I can.
I would like further comment on: post #149 by me and the reply #150 by CatalinaWOW then my follow up questions in post #151.
I suspect the ego battles between other parties will rage on regardless, probably tarring the whole thread with the same brush and causing it to be locked, but that is all I am interested in discussing and yet my thread gets dragged into the mud due to the other BS that has nothing to do with me.
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No, no and no! Absolutely not good enough!
Back in the good 'owd days, cars came with an ammeter which showed whether current was flowing into or out of the battery.
Then one day alternators became too powerful - it wasn't practical to pipe 100A or more to the dashboard to operate an ammeter. So ammeters were dropped and for at least a couple of decades cars came with a voltmeter on the dashboard instead.
The voltmeter was usually marked with coloured bands, and the idea was that if the voltmeter was in the green band you could assume the battery and charging system were working OK. If not, then there was a problem.
Voltmeters only disappeared with the more recent trend to do away with gauges and instead use warning lights and written fault descriptions (for example, my car has neither type of meter nor even a warning light, but it says "CHECK ALTERNATOR" on the information screen) .
But for a long time, voltmeters were provided as a means of the driver monitoring the health of the battery and charging system. Of course it wasn't perfect, but the industry and most of the users considered it to be useful enough to include one. Articles were written in motoring magazines about how to interpret the voltmeter.
I can tell you this (and I've just checked with a retired car technician from that era): not a single one of those voltmeters had its own pair of wires going all the way back to the battery terminals.
I feel sorry for @radiolistener because he's got himself into an unfortunate position which he cannot back out of (let's be honest, we've all been there), but he is of course right in theory when he says a voltmeter cannot alone provide a complete analysis of the battery condition and charging system function. But in practice it can provide a very helpful - and usually sufficient - indication that something is amiss.
That is all the OP needs at this juncture: is the warning light associated with a drop in battery voltage (which usually implies a drop in charging current)? And a way of monitoring this as he is driving around. More detailed analysis might be required later, but for now a voltmeter will do the job.
@radiolistener's position is contrary to standard practice across the car industry for a good two decades or so. The suggestion to plug in a voltmeter has extensive precedent.
Well explained :-+
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Anyway I have just had a Bosch expert explain to me that I am ok to connect to the dc-dc circuit so fight away! :box:
I do now blame radiolistener as being the agent provocateur for this whole debacle.
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No, of course not.
Proper testing of a battery is done with a specific charger/tester on the battery (without connection to the car).
I have never ever said or even mentioned that a battery can be fully tested by using a dmm connected on the cigarette lighter.
What I did say - at least tried to say- is that when measuring the voltage anywhere, and with experience and knowledge of how car electricity is generated, one can determine if there is somehow an issue with the battery or the charging system.
That is what TS can do (and honestly, I think the only thing he could or should do).
Of course you can measure the current with a clamp and we did that also when there was an indication of an issue somewhere in the car regarding the voltage.
You can also take the battery apart and refill it and log its behavior but that are not things a normal person would or should do.
Its like escalating a ticket to a support team: first it goes to first level, if they cannot solve it or think it is not up to them, them put in in the queue for second level and they possibly forward it to third level.
The same goes for any problem with a car (although with less support levels).
If we got a car with strange behavior, that car already passed the local dealer and probably some other technicians, with or without proper knowledge.
Radiolistener is putting words in my mouth, while all I tried to tell, with respect to TS, is that measuring the voltage anyhow and anywhere will give you (or experienced automotive technicians), already a clue of what is going on.
Like things that should be checked or can already be ruled out.
consider it as a first level support.
But we never send a battery to Varta (which is the manufacturer of the Bosch batteries) for testing in a lab.
You’re now trying to deflect responsibility by suggesting your earlier recommendations were misinterpreted.
I didn’t "put words in your mouth" - I simply quoted your own statements. For clarity, here’s exactly what you wrote:
I have been analyzing car electronics and car battery issues for more than 20 years.
You can reliably measure the battery voltage at any point in the car.
I’m telling its better to measure somewhere down the road instead of next to the battery.
Those who really are involved in automotive electronics know how to determine if a battery is charging or not by measuring voltage anywhere and knowing how to interpret it.
So now you want to say that I put those words in your mouth?
These are your exact words, not my interpretation. If you now wish to clarify or revise your position - please do so directly.
But your original your statements were very clear:
- You insisted that “measuring voltage anywhere” can allow assessment of the battery and charging system condition.
- You presented this approach as practical advice, not as a theoretical "first-level triage"
Now you're framing this as just an initial step that can give "a clue" while avoiding responsibility for previously recommending such measurements as reliable.
To clarify once more: Is your position that voltage measurements from random points like the cigarette lighter are sufficient for reliable alternator/charging diagnostics without opening the hood and measuring charging current? Yes or no?
Please provide a clear, unambiguous answer. Avoid generalizations or metaphors like “support levels”.
This is not a helpdesk ticket - this is real-world diagnostics.
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Anyway I have just had a Bosch expert explain to me that I am ok to connect to the dc-dc circuit so fight away! :box:
He is not an expert, but a spreader of misinformation who first posts falsehoods, then avoids taking responsibility for what he wrote, and even tries to shift the blame onto those who disproved him - claiming "they put words in his mouth". It is highly unlikely he has any official connection to Bosch, and certainly his statements do not represent Bosch’s genuine recommendations.
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No, of course not.
Proper testing of a battery is done with a specific charger/tester on the battery (without connection to the car).
I have never ever said or even mentioned that a battery can be fully tested by using a dmm connected on the cigarette lighter.
What I did say - at least tried to say- is that when measuring the voltage anywhere, and with experience and knowledge of how car electricity is generated, one can determine if there is somehow an issue with the battery or the charging system.
That is what TS can do (and honestly, I think the only thing he could or should do).
Of course you can measure the current with a clamp and we did that also when there was an indication of an issue somewhere in the car regarding the voltage.
You can also take the battery apart and refill it and log its behavior but that are not things a normal person would or should do.
Its like escalating a ticket to a support team: first it goes to first level, if they cannot solve it or think it is not up to them, them put in in the queue for second level and they possibly forward it to third level.
The same goes for any problem with a car (although with less support levels).
If we got a car with strange behavior, that car already passed the local dealer and probably some other technicians, with or without proper knowledge.
Radiolistener is putting words in my mouth, while all I tried to tell, with respect to TS, is that measuring the voltage anyhow and anywhere will give you (or experienced automotive technicians), already a clue of what is going on.
Like things that should be checked or can already be ruled out.
consider it as a first level support.
But we never send a battery to Varta (which is the manufacturer of the Bosch batteries) for testing in a lab.
You’re now trying to deflect responsibility by suggesting your earlier recommendations were misinterpreted.
I didn’t "put words in your mouth" - I simply quoted your own statements. For clarity, here’s exactly what you wrote:
I have been analyzing car electronics and car battery issues for more than 20 years.
You can reliably measure the battery voltage at any point in the car.
I’m telling its better to measure somewhere down the road instead of next to the battery.
Those who really are involved in automotive electronics know how to determine if a battery is charging or not by measuring voltage anywhere and knowing how to interpret it.
So now you want to say that I put those words in your mouth?
These are your exact words, not my interpretation. If you now wish to clarify or revise your position - please do so directly.
But your original your statements were very clear:
- You insisted that “measuring voltage anywhere” can allow assessment of the battery and charging system condition.
- You presented this approach as practical advice, not as a theoretical "first-level triage"
Now you're framing this as just an initial step that can give "a clue" while avoiding responsibility for previously recommending such measurements as reliable.
To clarify once more: Is your position that voltage measurements from random points like the cigarette lighter are sufficient for reliable alternator/charging diagnostics without opening the hood and measuring charging current? Yes or no?
Please provide a clear, unambiguous answer. Avoid generalizations or metaphors like “support levels”.
This is not a helpdesk ticket - this is real-world diagnostics.
I’m here to help TS.
It seems you are not.
I have explained several times how I would approach the issue of TS.
If you don’t agree, fine.
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Anyway I have just had a Bosch expert explain to me that I am ok to connect to the dc-dc circuit so fight away! :box:
He is not an expert, but a spreader of misinformation. It is highly unlikely he has any official connection to Bosch, and certainly his statements do not represent Bosch’s genuine recommendations.
I feel honored you’re thinking I’m the guy that TS contacted.
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who said ya cant diagnose by reading a voltage,wot about measuring the voltage on the wire between the battery and alternator,that'll tell you if the alternator is chucking anything out and how much
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I’m here to help TS.
It seems you are not.
I have explained several times how I would approach the issue of TS.
If you don’t agree, fine.
I will submit an official inquiry to Bosch referencing this thread to verify whether you are an authorized Bosch representative and if your statements align with Bosch’s official position and guidelines on this matter. Lets see what they answer. :)
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I’m here to help TS.
It seems you are not.
I have explained several times how I would approach the issue of TS.
If you don’t agree, fine.
I will submit an official inquiry to Bosch referencing this thread to verify whether you are an authorized Bosch representative and if your statements align with Bosch’s official position and guidelines on this matter. Lets see what they answer. :)
You are, again, making your own truth.
It s getting annoying
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You are, again, making your own truth.
It s getting annoying
I am relying on facts, not “my own truth”. If you claim to represent Bosch, please provide official references or documentation supporting your statements. Otherwise, it’s difficult to take your claims seriously.
We will also wait for Bosch’s official response to verify whether their policies align with your statements and to confirm if you are indeed speaking on behalf of Bosch or merely posting misinformation while falsely invoking their name.
Such behavior raises doubts about your actual affiliation with Bosch. A genuine representative would communicate respectfully to uphold the company’s reputation.
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You can. As long as you are careful routing said wire past metal edges there are no reasons except possibly cosmetic not to.
Will it only take the amps it wants then and the whole 40+ when the charger is running won't go to it?
EDIT: Hmm as I think about it, if we forget about the cable run, it is the equivalent to having both plugged right into the starter battery terminals isn't it? So whether both are wired direct at the terminal or at the end of a long run of wire, it is the same right? So it should be the same case that the voltmeter would not pull more amps when the dc-dc charger is running, than if it were also connected at the battery terminal posts itself. Is that right?
Can you explain what being careful about routing past metal edges means in this context? Is it anything different from normal circuits of not having exposed wires touching metal? If the worst happened and they did touch what would happen? Won't the ground to the metal chasis make it safe? Not that I intend for it, just to know the safety parameters.
I already have this (https://www.12voltplanet.co.uk/marine-battery-isolator-switch-with-removable-actuator-2-positions-200a-continuous.html) battery isolator switch in place between the start battery positive and dc-dc charger positive input so I can disable it when I don't want it in use. I was thinking I could just connect the positive for the voltmeter to the positive terminal on the starter battery side there. Would that work?
In this case I would not be making any kind of junctions or routing and just adding the little voltmeter wire to that existing terminal which would be a safe bet right?
Then just run the negative to the common negative busbar for the leisure battery.
Can you explain to me, if this is ok, why the amps would not burst into the voltmeter too when the charger is running?
If you connect smaller wire rated at a lower current to a high current circuit, or direct to the battery terminals, and it chafes on a sharp metal edge somewhere or otherwise short-circuits, the worst that could happen is total loss of the vehicle due to an electrical fire. The resistance of the small wire can limit the short-circuit current sufficiently that it doesn't blow any fuse or other circuit protection on the high current circuit, but the very high overload current through the small wire can still get that wire red-hot, melting its insulation and igniting it and anything flammable nearby. If you short an un-fused circuit in a vehicle, you are *LUCKY* if you catch it quickly enough to limit the damage to having to replace a half-melted wiring loom (as even a few seconds shorted can get the wire hot enough to melt its own insulation and melt into the insulation of any wires its bundled with, compromising them). That's at least several hundred bucks damage in parts and labour as the *BEST* *POSSIBLE* outcome!
This id why I and a few others have said you need an inline fuse as close as possible to where you tap off from the positive battery terminal or other high current circuit. The short wire between the fuse and the high current circuit is much less at risk (but best practice would be to put it in sleeving for added protection) and everything in your new wiring downstream of the fuse is protected.
Whether or not you can and should tap into another circuit to connect your voltmeter depends on the accuracy you need and whether or not that circuit is heavily loaded when the vehicle is running. If your high current charger circuit is never used when driving, it could be an ideal way of getting the battery terminal voltage nearly as accurately as going direct to the battery. Note your voltmeter is only three digit with 0.1V resolution.
@ Sorama & Radiolistener.
(https://imgs.xkcd.com/comics/duty_calls.png)
https://xkcd.com/386/ (https://xkcd.com/386/)
Please consider taking a break from this topic. Neither of you is going to convince the other, and you've already got Simon wound up enough to be talking about possibly locking the topic! Thank you.
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Yes, at this point, there’s nothing more to add - let’s wait for the official Bosch response. It will be interesting to learn Bosch official position on this matter. :popcorn:
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You are, again, making your own truth.
It s getting annoying
I am relying on facts, not “my own truth”. If you claim to represent Bosch, please provide official references or documentation supporting your statements. Otherwise, it’s difficult to take your claims seriously.
We will also wait for Bosch’s official response to verify whether their policies align with your statements and to confirm if you are indeed speaking on behalf of Bosch or merely posting misinformation while falsely invoking their name.
Such behavior raises doubts about your actual affiliation with Bosch. A genuine representative would communicate respectfully to uphold the company’s reputation.
Sure.
You want me to wire you some money too?
Really, you should stop it.
You’re making a fool of yourself.
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If you connect smaller wire rated at a lower current to a high current circuit, or direct to the battery terminals, and it chafes on a sharp metal edge somewhere or otherwise short-circuits, the worst that could happen is total loss of the vehicle due to an electrical fire. The resistance of the small wire can limit the short-circuit current sufficiently that it doesn't blow any fuse or other circuit protection on the high current circuit, but the very high overload current through the small wire can still get that wire red-hot, melting its insulation and igniting it and anything flammable nearby. If you short an un-fused circuit in a vehicle, you are *LUCKY* if you catch it quickly enough to limit the damage to having to replace a half-melted wiring loom (as even a few seconds shorted can get the wire hot enough to melt its own insulation and melt into the insulation of any wires its bundled with, compromising them). That's at least several hundred bucks damage in parts and labour as the *BEST* *POSSIBLE* outcome!
This id why I and a few others have said you need an inline fuse as close as possible to where you tap off from the positive battery terminal or other high current circuit. The short wire between the fuse and the high current circuit is much less at risk (but best practice would be to put it in sleeving for added protection) and everything in your new wiring downstream of the fuse is protected.
Oh right, so it is just the usual considerations with wires and fusing, not anything special about this particular case of tapping the DC charger run?
Yes I have bought an inline fuse for the voltmeter wire at the same time I bought it.
Whether or not you can and should tap into another circuit to connect your voltmeter depends on the accuracy you need and whether or not that circuit is heavily loaded when the vehicle is running. If your high current charger circuit is never used when driving, it could be an ideal way of getting the battery terminal voltage nearly as accurately as going direct to the battery. Note your voltmeter is only three digit with 0.1V resolution.
It is the opposite, the dc-dc charger only charges when the engine is running as it is charge the leisure battery from the alternator, via the starter battery, by putting a load on it. The charger is rated at 60A.
Why would the charger running be an issue for the voltage? The device itself has a voltmeter to check the starter battery as well as the leisure battery, while running, but only for diagnostics, not for real-time checking as it is nestled deep in my van but when I have looked at it in the past it has not shown a difference of anything considerable to at the starter terminals itself. In fact in doing diagnostics in the past, nothing to do with this particular case, but when the charger itself was malfunctioning, I was told to check the voltages at the charger and the starter terminals were the same by using a multimeter on the starter and did not see any discrepancy. In fact the dc charger itself is woken up by the voltage on the starter battery itself when it goes above something int he 13v range which is the indicator the engine is running so it starts is charging process.
So why would it running or not have any bearing on the littler voltmeter I want to put on? Given the above I think it is designed to not interfere with the normal voltages of the starter.
Can you explain to me my other query on why the voltmeter circuit would not blow if put on this wire when the dc-dc charger was sucking 60A through that main line? Why doesn't any of that current go up the little voltmeter wire on the way to its destination?
@ Sorama & Radiolistener.
Please consider taking a break from this topic. Neither of you is going to convince the other, and you've already got Simon wound up enough to be talking about possibly locking the topic! Thank you.
Yea this was a good informative post and what I have been trying to tease out for so many pages. :scared: Not fair if my thread gets locked as I have had nothing, or very little, to do with all the garbage in it.
I don't personally mind the back and forth jousting as there have been some interesting anecdotes in the reparte too but it should not cause the thread to get locked on that account. I don't see why the thread should be locked due to that anyway. If people don't like it they can just go to another thread.
I am not encouraging it but don't see why it should be censored.
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That is interesting background information but does not address what I am asking - how to wire it if I don't want to use the 12v port.
I asked earlier, can I wire it to the existing wires running from the starter battery into the van's dc-dc charger circuit to which CatalinaWOW noted that yes I can.
I would like further comment on: post #149 by me and the reply #150 by CatalinaWOW then my follow up questions in post #151.
I suspect the ego battles between other parties will rage on regardless, probably tarring the whole thread with the same brush and causing it to be locked, but that is all I am interested in discussing and yet my thread gets dragged into the mud due to the other BS that has nothing to do with me.
Well what are you asking for? so you don't want to use the socket, ok so you could find a place somewhere else. Have you mentioned what vehicle it is? have you consulted its manual and electrical schematics? what is the purpose of this thread? Are you just trolling? looking at your email address and username I'd ban you as a spam account in a heartbeat normally.
Are you actually incapable of simply finding a suitable spur from your vehicles distribution board that is not loaded by much?
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Hahaha, what a sh*tshow of a thread. I haven't seen worse in a while :-DD
Just to add some real input here, from real life. I'm not a car technician, but use to fix my own cars a lot. A couple of weeks ago, my kid called that the car stopped while he was driving and didn't turn on again. I suspected the alternator (it's an old car). It was half an hour away, so I drove there and checked the battery voltage (happened to be from the battery terminals, but I don't care Correction, from the terminals in the engine bay; this car has the battery in the trunk). It showed about 12 V. Tried to start the car and it actually started. Now measuring the voltage again and saw that it dropped fast and within a minute the car stopped when the voltage dropped under 10 V or so. Alternator definitely broken.
Took out the battery, it's a good old 100 Ah (Mercedes petrol engine), took it home and charged it overnight. Drove back next day, BOUGHT a CHEAP 10 € CIGARETTE LIGHTER VOLTMETER for monitoring the battery, installed the battery and had him drive home while following in the other car. Lights turned off, of course and fan on lowest setting. Had him monitor the voltage on the cigarette lighter socket voltmeter and it stayed over 12.5 V or so all the way (about 40 km). I'm sure the battery could have lasted an hour without charging. Replaced the alternator and the car was back on the road again. It shows over 14 V when charging.
Point is, in majority of cases the alternator works, or it's broken, and a cheap voltmeter will show if it's broken or not. And that's what you want to know in these cases. Doesn't matter where you measure the voltage. Now I'm not saying there are other cases where you need more analysis, but that's done in a car garage or workshop, not on the road.
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That is interesting background information but does not address what I am asking - how to wire it if I don't want to use the 12v port.
I asked earlier, can I wire it to the existing wires running from the starter battery into the van's dc-dc charger circuit to which CatalinaWOW noted that yes I can.
I would like further comment on: post #149 by me and the reply #150 by CatalinaWOW then my follow up questions in post #151.
I suspect the ego battles between other parties will rage on regardless, probably tarring the whole thread with the same brush and causing it to be locked, but that is all I am interested in discussing and yet my thread gets dragged into the mud due to the other BS that has nothing to do with me.
Well what are you asking for? so you don't want to use the socket, ok so you could find a place somewhere else. Have you mentioned what vehicle it is? have you consulted its manual and electrical schematics? what is the purpose of this thread? Are you just trolling? looking at your email address and username I'd ban you as a spam account in a heartbeat normally.
Are you actually incapable of simply finding a suitable spur from your vehicles distribution board that is not loaded by much?
Why do you keep chastising me making accusations for things I answer in posts only a couple posts before?
Ye I use random names and emails for forum accounts because I don't want constant email spam to my main account so what?
Why am I getting the heat for all the argumentation that has gone in this thread already? I have been a model poster so far on this forum and I am getting in trouble due to this one thread of which the trouble has had nothing to do with me it just coincidentally happened in my thread.
If you actually took the time to read my post history you would see I am not a troll and have asked genuine questions for my posts yet for some reason you are trying to paint me as the ringleader just because you haven't bothered to read the thread properly. Fine if you don't want to to read it but don't make accusations about me doing bad when it has had nothing to do with me.
I don't get why you are directing all the blame on me while it is the other two that are going at each other.
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Sure.
You want me to wire you some money too?
Really, you should stop it.
You’re making a fool of yourself.
If your comment was intended as a joke about some kind of informal "arrangement" offer - let me clarify: I have no interest in any form of corruption or illegal practices such as bribery. My only goal is to receive clear, professional answers based on official information. Let’s wait for Bosch’s official response instead of engaging in pointless sarcasm.
Just to remind you - it was you who presented yourself as a Bosch expert with 20 years of experience. If you claim such credentials, it’s reasonable to expect clear, professional answers and accountability for your statements.
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Hahaha, what a sh*tshow of a thread. I haven't seen worse in a while :-DD
Just to add some real input here, from real life. I'm not a car technician, but use to fix my own cars a lot. A couple of weeks ago, my kid called that the car stopped while he was driving and didn't turn on again. I suspected the alternator (it's an old car). It was half an hour away, so I drove there and checked the battery voltage (happened to be from the battery terminals, but I don't care Correction, from the terminals in the engine bay; this car has the battery in the trunk). It showed about 12 V. Tried to start the car and it actually started. Now measuring the voltage again and saw that it dropped fast and within a minute the car stopped when the voltage dropped under 10 V or so. Alternator definitely broken.
Took out the battery, it's a good old 100 Ah (Mercedes petrol engine), took it home and charged it overnight. Drove back next day, BOUGHT a CHEAP 10 € CIGARETTE LIGHTER VOLTMETER for monitoring the battery, installed the battery and had him drive home while following in the other car. Lights turned off, of course and fan on lowest setting. Had him monitor the voltage on the cigarette lighter socket voltmeter and it stayed over 12.5 V or so all the way (about 40 km). I'm sure the battery could have lasted an hour without charging. Replaced the alternator and the car was back on the road again. It shows over 14 V when charging.
Point is, in majority of cases the alternator works, or it's broken, and a cheap voltmeter will show if it's broken or not. And that's what you want to know in these cases. Doesn't matter where you measure the voltage. Now I'm not saying there are other cases where you need more analysis, but that's done in a car garage or workshop, not on the road.
I have been telling this for euh…Pages.
:-+
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If your comment was intended as a joke about some kind of informal "arrangement" offer - let me clarify: I have no interest in any form of corruption or illegal practices such as bribery.
Ok.
I wasn’t going to do that anyway…
What country are you from ?
Or world…
:palm:
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Took out the battery, it's a good old 100 Ah (Mercedes petrol engine), took it home and charged it overnight. Drove back next day, BOUGHT a CHEAP 10 € CIGARETTE LIGHTER VOLTMETER for monitoring the battery, installed the battery and had him drive home while following in the other car. Lights turned off, of course and fan on lowest setting. Had him monitor the voltage on the cigarette lighter socket voltmeter and it stayed over 12.5 V or so all the way (about 40 km). I'm sure the battery could have lasted an hour without charging. Replaced the alternator and the car was back on the road again. It shows over 14 V when charging.
Oh that is another good use case, besides to see if the alternator is function with above 13v, for using one. Good point.
I had made other posts related to this...about linking the starter and leisure battery in parallel if the vehicle just 'stopped', as in the case of your son, so that I could get some charge back in the starter to drive it a way and then repeat the process. In this case the voltmeter would be very handy to check how much there was left while driving to tactically plan the next pitstop.
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Took out the battery, it's a good old 100 Ah (Mercedes petrol engine), took it home and charged it overnight. Drove back next day, BOUGHT a CHEAP 10 € CIGARETTE LIGHTER VOLTMETER for monitoring the battery, installed the battery and had him drive home while following in the other car. Lights turned off, of course and fan on lowest setting. Had him monitor the voltage on the cigarette lighter socket voltmeter and it stayed over 12.5 V or so all the way (about 40 km). I'm sure the battery could have lasted an hour without charging. Replaced the alternator and the car was back on the road again. It shows over 14 V when charging.
Oh that is another good use case, besides to see if the alternator is function with above 13v, for using one. Good point.
I had made other posts related to this...about linking the starter and leisure battery in parallel if the vehicle just 'stopped', as in the case of your son, so that I could get some charge back in the starter to drive it a way and then repeat the process. In this case the voltmeter would be very handy to check how much there was left while driving to tactically plan the next pitstop.
Oh oh…
I didn’t see that one coming.
I should stop drinking.
Or start drinking more.
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Point is, in majority of cases the alternator works, or it's broken, and a cheap voltmeter will show if it's broken or not.
That’s not entirely correct. In many cases, alternators don’t fail completely - they develop partial faults like bad current, regulator malfunctions, etc. These issues can’t be reliably detected with a simple voltmeter, especially when measuring "anywhere".
I’ve personally encountered such failures and they’re fairly common, though often go unnoticed, with people continuing to drive with a malfunctioning alternator. This typically leads to premature battery failure. Therefore, if a battery degrades unusually fast (for example, fail within 6-12 months), checking the alternator should be a priority.
The point is, if the alternator fails completely, you’ll likely notice it quickly even without any voltmeter. However, in case of a partial failure, identifying the problem can be much more difficult.
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Point is, in majority of cases the alternator works, or it's broken, and a cheap voltmeter will show if it's broken or not.
That’s not entirely correct. In many cases, alternators don’t fail completely - they develop partial faults like bad current, regulator malfunctions, etc. These issues can’t be reliably detected with a simple voltmeter, especially when measuring "anywhere".
I’ve personally encountered such failures and they’re fairly common, though often go unnoticed, with people continuing to drive with a malfunctioning alternator. This typically leads to premature battery failure. Therefore, if a battery degrades unusually fast (for example, fail within 6-12 months), checking the alternator should be a priority.
The point is, if the alternator fails completely, you’ll likely notice it quickly even without any voltmeter. However, in case of a partial failure, identifying the problem can be much more difficult.
Bad current?
So there is good current also?
Are we sure this ain’t some evil AI?
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Bad current?
So there is good current also?
"Bad" in this context means incorrect, insufficient, out of specification, etc.
"Good" means within specification, as expected.
Such nuances should be clear to an automotive engineer and Bosch battery diagnostics expert with 20 years of experience, as you introduced yourself here. Wouldn’t you agree?
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Bad current?
So there is good current also?
Are we sure this ain’t some evil AI?
Actually there could be "bad current" depending on your definition. It's where the diode-trio or a rectifier diode fails in the alternator.
It will have weak output current, or pulsating high-ripple voltage output. Not nice 3-ph rectified DC output.
Toyota Landcruiser, 13.8V at the battery but it could not charge the battery. Had me stumped but it was shorted rectifier(s). The regulator controlled to an average voltage, which is wrong when you have high ripple some AC present.
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Bad current?
So there is good current also?
"Bad" in this context means incorrect, insufficient, out of specification, etc.
"Good" means within specification, as expected.
Such nuances should be clear to an automotive engineer and Bosch battery diagnostics expert with 20 years of experience, as you introduced yourself here. Wouldn’t you agree?
English is not my language.
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I love this thread! I'm just popping out for some more popcorn...
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You're going to overdose on popcorn lol. :popcorn: :popcorn: :popcorn:
I don't know why people here on EEVblog have to be so hard ass, especially in a beginner's thread.
Of course many people speak different languages, use different terminology, different words. Different experience, education as well.
It's amazing to see one number- a voltage reading - cause so much mud to be slung around. And we still have no progress on OP's problem with the van, that I can read.
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To the OP:
The suspense is killing us here!
Please, if you would: either
- Connect a voltmeter to your lighter socket, or
- Connect a wire somewhere to the switched 12 volts (after the ignition switch) and connect that to a voltmeter
Either one will work as well. If you connect a wire, just be sure to make good connections at both ends.
Size doesn't really matter, as the voltmeter will draw pretty close to zero current.
If you want to use the lighter socket for something else, I think you can get cigarerette-lighter socket extenders to give you a 2nd (or 3rd) socket.
And of course, please report back your measurements.
We're counting on you!
In the meantime, more popcorn!
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May be I mount one of my DMM in the engine compartment connect the test lead to the battery and use fluke connect to my phone so I can take the reading in the car. Wire another to a cigarette lighter plug and check the voltage there. That way I can compare the reading in different conditions.
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You're going to overdose on popcorn lol. :popcorn: :popcorn: :popcorn:
I don't know why people here on EEVblog have to be so hard ass, especially in a beginner's thread.
Of course many people speak different languages, use different terminology, different words. Different experience, education as well.
It's amazing to see one number- a voltage reading - cause so much mud to be slung around. And we still have no progress on OP's problem with the van, that I can read.
Well, maybe soon we’ll see some professional recommendations and comments directly from Bosch...
:popcorn: :popcorn: :popcorn:
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In an indirect answer to the OPs questions.
1. There is no need to worry about the starter draw. A voltmeter has high impedance. At 12 volts only tiny fractions of n amp will flow through it. Use the water analogy for current. You can tap a large diameter pipe with a small straw size hole. While that large pipe may have hundreds of liters per minute flowing through it only relatively small volumes will escape through the small hole.
2. The caution about sharp edges relates to the possibility of chafing through the insulation causing a short circuit. That is a fire hazard.
3. While the best measurement would be a wire straight to the terminals, any connection will give quite usable information. First it is giving the voltage available to the system which is useful. Second, if the car starts there can't be much resistance in the connection to the battery. Usually much less than an ohm. So with normal current draws the voltage should be within a modest fraction of a volt from the actual battery voltage. Watching for voltage change when adding a significant load, like turning on the headlights will give insight.
As a final comment. If the OP is not trolling with a pretense of ignorance the following comment may be useful. There must be two connections to the voltmeter. The negative is commonly hooked to the chassis, but chassis connectionsare notorious for developing faults. It would be wise to measure resistance between your contemplated point of attachment and the negative terminal of the battery.
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Well, maybe soon we’ll see some professional recommendations and comments directly from Bosch...
I don't think anyone is bothered about what Bosch says, are they? You can get any answer you want just by phrasing the question appropriately.
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I believe relying on official sources is always better than accepting random personal opinions, especially when safety and proper diagnostics are involved. Bosch response will help clarify whether certain statements were personal interpretations or actual company recommendations.
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I'm waiting for the OP to actually connect up a voltmeter and report their results back to us.
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I remember 30 amp fuses to the cigarette lighter in the old days. I think most are just a few amp "power connector" now for a standard.
In newer cars i had to carry a can of freeze spray, until tolls went up over the cost of a dime or so that you could heat up in the lighter for the toll taker. At least the freeze spray coins "surprise" would not permanently burn their hand.
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I've used this with great results. When not charging, it acts as a volt meter:
https://www.amazon.com/dp/B0B1X6SS92?ref_=ppx_hzsearch_conn_dt_b_fed_asin_title_3 (https://www.amazon.com/dp/B0B1X6SS92?ref_=ppx_hzsearch_conn_dt_b_fed_asin_title_3)
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And we still have no progress on OP's problem with the van, that I can read.
There is some but it is painstakingly slow as my questions seems to get lost in the shuffle and I have to ask again and again to get a response to the issues I am actually asking.
If you look at posts: # 149, 150, 151, then jump to 179. Then post 182 for my current queries, specifically:
Can you explain to me my other query on why the voltmeter circuit would not blow if put on this wire when the dc-dc charger was sucking 60A through that main line? Why doesn't any of that current go up the little voltmeter wire on the way to its destination?
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To the OP:
The suspense is killing us here!
Please, if you would: either
- Connect a voltmeter to your lighter socket, or
- Connect a wire somewhere to the switched 12 volts (after the ignition switch) and connect that to a voltmeter
Either one will work as well. If you connect a wire, just be sure to make good connections at both ends.
Size doesn't really matter, as the voltmeter will draw pretty close to zero current.
If you want to use the lighter socket for something else, I think you can get cigarerette-lighter socket extenders to give you a 2nd (or 3rd) socket.
And of course, please report back your measurements.
We're counting on you!
In the meantime, more popcorn!
Suspense about what? I have already stated many times through the thread I know the alternator is working fine. I just want to install a voltmeter NOT on the 12v socket and rather on its own wired circuit and the question which I have been asking from the beginning is how best to do that and the post I wrote above is a summation of the recent few posts which finally delve into the relevant subject matter to my question.
The rest of the stuff about wanting me to read from the 12v port is the co-opted agenda of other members, not mine.
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I'm waiting for the OP to actually connect up a voltmeter and report their results back to us.
Umm as I have been saying time and time again if anyone actually read my posts I have done that loads of times already even before making the post.
It is nothing to do with whether my alternator is working at this present time. It is about having a gauge to check it is still in good working order while driving that I can refer to.
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I'm waiting for the OP to actually connect up a voltmeter and report their results back to us.
Umm as I have been saying time and time again if anyone actually read my posts I have done that loads of times already even before making the post.
It is nothing to do with whether my alternator is working at this present time. It is about having a gauge to check it is still in good working order while driving that I can refer to.
I’m still convinced you do not see nor understand the relevance of what we ( except for radio listener) have been saying, precisely your concern.
You think we are off topic but we are not: you just don’t see the underlying thinking and the importance of it.
As long as you don’t make that click in your head, it will be difficult for you to see all the help and solutions we are giving you.
If you can’t understand the technical reasoning behind it, then that is fine for me (really), but then you will have to literally accept and do exactly what we tell you to do.
The feedback we are asking you is to understand what is happening with your car so we can, again, give you some insights.
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I'm waiting for the OP to actually connect up a voltmeter and report their results back to us.
Umm as I have been saying time and time again if anyone actually read my posts I have done that loads of times already even before making the post.
It is nothing to do with whether my alternator is working at this present time. It is about having a gauge to check it is still in good working order while driving that I can refer to.
I’m still convinced you do not see nor understand the relevance of what we ( except for radio listener) have been saying, precisely your concern.
You think we are off topic but we are not: you just don’t see the underlying thinking and the importance of it.
As long as you don’t make that click in your head, it will be difficult for you to see all the help and solutions we are giving you.
If you can’t understand the technical reasoning behind it, then that is fine for me (really), but then you will have to literally accept and do exactly what we tell you to do.
The feedback we are asking you is to understand what is happening with your car so we can, again, give you some insights.
As I have repeated there is no problem with the operation of the vehicle that I am asking for help with.
All I have been asking for in this whole thread has been advice on wiring a new component.
THERE IS NO MALFUNCTION THAT NEEDS ADDRESSING. That is what you must understand. Therefore there there is no point getting diagnostics where there is no problem.
I have said over and over again the alternator is working fine. I just want to add a voltmeter to keep being able to monitor that it continues to run fine when driving.
It is merely a technical question about how best to wire the voltmeter. NOT a question about 'what is wrong with my vehicle/alternator?'
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If you don't want to tap directly from your car's
cigarette lighter power port, take a look at this.
These fuse taps are commonly used when adding a backup camera to an older car.
https://www.youtube.com/watch?v=zm0KRm7jy_g (https://www.youtube.com/watch?v=zm0KRm7jy_g)
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I'm waiting for the OP to actually connect up a voltmeter and report their results back to us.
Umm as I have been saying time and time again if anyone actually read my posts I have done that loads of times already even before making the post.
It is nothing to do with whether my alternator is working at this present time. It is about having a gauge to check it is still in good working order while driving that I can refer to.
I’m still convinced you do not see nor understand the relevance of what we ( except for radio listener) have been saying, precisely your concern.
You think we are off topic but we are not: you just don’t see the underlying thinking and the importance of it.
As long as you don’t make that click in your head, it will be difficult for you to see all the help and solutions we are giving you.
If you can’t understand the technical reasoning behind it, then that is fine for me (really), but then you will have to literally accept and do exactly what we tell you to do.
The feedback we are asking you is to understand what is happening with your car so we can, again, give you some insights.
As I have repeated there is no problem with the operation of the vehicle that I am asking for help with.
All I have been asking for in this whole thread has been advice on wiring a new component.
THERE IS NO MALFUNCTION THAT NEEDS ADDRESSING. That is what you must understand. Therefore there there is no point getting diagnostics where there is no problem.
I have said over and over again the alternator is working fine. I just want to add a voltmeter to keep being able to monitor that it continues to run fine when driving.
It is merely a technical question about how best to wire the voltmeter. NOT a question about 'what is wrong with my vehicle/alternator?'
Are you sure, because your own very first question when you started the topic is about a potential issue:
I just had the idea to get one of these due to not trusting the intermittent battery light so then I can monitor the actual voltage when driving without having to pop the hood at a layby and check manually when that light is coming on and off.
I have been monitoring it more regularly now after driving and so far have not seen any decline in voltage when I park up so doesn't seem to be an indicator of battery drainage.
Btw could the light coming on be an indication of the voltage being too high rather than too low? I did read in the manual and it did not indicate that as a reason it would come on from what I recall. .
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If you don't want to tap directly from your car's cigarette lighter power port, take a look at this.
These fuse taps are commonly used when adding a backup camera to an older car.
https://www.youtube.com/watch?v=zm0KRm7jy_g (https://www.youtube.com/watch?v=zm0KRm7jy_g)
Youtube is blocked for me, but the general term is fuse taps?
As was discussed the most straight forward for me will be to route it from the dc-dc charger battery cable circuit. Due to large size difference in wires I am thinking to just wrap the little wire around the terminal post of the battery isolator switch between starter battery positive and dc-dc charger input positive. Also with inline fuse. Sounds ok?
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Are you sure, because your own very first question when you started the topic is about a potential issue:
I just had the idea to get one of these due to not trusting the intermittent battery light so then I can monitor the actual voltage when driving without having to pop the hood at a layby and check manually when that light is coming on and off.
I have been monitoring it more regularly now after driving and so far have not seen any decline in voltage when I park up so doesn't seem to be an indicator of battery drainage.
Btw could the light coming on be an indication of the voltage being too high rather than too low? I did read in the manual and it did not indicate that as a reason it would come on from what I recall. .
Yes because I am not asking for a solution to that in this thread which I have already made other threads discussing. It was only mentioned to give background on why I am adding it. The point is that the light coming on is what I believe to be a false positive having checked at the terminals and the increase in voltage indicating charge and alternator spinning normally.
You will keep on that now of course to have some more material to argue about.
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I'm waiting for the OP to actually connect up a voltmeter and report their results back to us.
Umm as I have been saying time and time again if anyone actually read my posts I have done that loads of times already even before making the post.
It is nothing to do with whether my alternator is working at this present time. It is about having a gauge to check it is still in good working order while driving that I can refer to.
I’m still convinced you do not see nor understand the relevance of what we ( except for radio listener) have been saying, precisely your concern.
You think we are off topic but we are not: you just don’t see the underlying thinking and the importance of it.
As long as you don’t make that click in your head, it will be difficult for you to see all the help and solutions we are giving you.
If you can’t understand the technical reasoning behind it, then that is fine for me (really), but then you will have to literally accept and do exactly what we tell you to do.
The feedback we are asking you is to understand what is happening with your car so we can, again, give you some insights.
As I have repeated there is no problem with the operation of the vehicle that I am asking for help with.
All I have been asking for in this whole thread has been advice on wiring a new component.
THERE IS NO MALFUNCTION THAT NEEDS ADDRESSING. That is what you must understand. Therefore there there is no point getting diagnostics where there is no problem.
I have said over and over again the alternator is working fine. I just want to add a voltmeter to keep being able to monitor that it continues to run fine when driving.
It is merely a technical question about how best to wire the voltmeter. NOT a question about 'what is wrong with my vehicle/alternator?'
and I have already tod you, find a wire that carries power that is accessible in the cab, preferably one that is not heavily loaded and put your meter on it. I don't know how much you are willing to mess with the vehicle but you could go into the back of the power socket if all you are using it for is a satnav or phone charger etc. So once again, what do you want? talking about it won't make it happen, you need to do something.
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May be I mount one of my DMM in the engine compartment connect the test lead to the battery and use fluke connect to my phone so I can take the reading in the car. Wire another to a cigarette lighter plug and check the voltage there. That way I can compare the reading in different conditions.
I checked mine yesterday since we were all talking about this.
The reading from the cigar lighter went down by 50mv with the headlights turned on, not high beams just low beams. That's just 0.050 volts (around 0.5 percent), which is a small amount but since I take all the readings without the lights on I will continue to do it that way.
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So once again, what do you want? talking about it won't make it happen, you need to do something.
I have clearly said what I want in other posts, but you only read the latest one and then have a go at me based off of a tiny snapshot of the whole thread without context.
I know what I intend to do now and had been discussing it just a few posts up with other users.
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I know better as well, but it's a first step. If the voltage is about right then the alternator is working. If it's low then investigate further with a more inconvenient but more accurate method.
If the best way is the hard way and something that will give some good pointers while not definitive is easy then start with the easy. 7 pages, ok including a load of political crap.
Ha ha, I know what you mean about the political junk posts.
I checked mine from the cigar lighter yesterday. With the low beam headlights on the reading dropped by just 0.050 volts. Now with other cars it could be more or less.
I don't take readings with the lights on though so I will just continue to do it that way for my history log. I have logs that go back years now.
I almost forgot to mention that I used a meter made just for a cigar lighter socket. I've used that one for a long time and it has 10mv resolution.
If I do use another one, I first correlate the readings from the regular one to the next one in case they different by a few millivolts or more.
I've gotten really good results using a battery operated oscilloscope. That's really good for testing the battery because you can see how the battery behaves when you first start the car. You can see how deep the dip goes when the starter first starts to turn over to start the engine, then how it tapers back up to a more normal voltage.
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Can you explain to me my other query on why the voltmeter circuit would not blow if put on this wire when the dc-dc charger was sucking 60A through that main line? Why doesn't any of that current go up the little voltmeter wire on the way to its destination?
A voltmeter has high impedance and isn't affected by the current directly. You can have 1000 A in that "main line" and any voltmeter will still be able to measure the voltage in any point of the "main line". The current through the voltmeter itself is determined by the _voltage_ between its terminals and the internal resistance of the voltmeter. A typical DC voltmeter has 100 kΩ to 10 MΩ input resistance (cheap meters might have lower and expensive ones higher). You can calculate the current through it using Ohm's law. This is basic fundamental electrical theory. I suggest you read about how voltmeters work.
The above are the basics. High DC currents could induce voltage transients at power-on and power-off. A really cheap voltmeter might have bad protection circuitry and its internals could be damaged due to high voltage spikes. But most DC-DC converters are built to not cause large voltage spikes, or they would also damage other electronic equipment.
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Can you explain to me my other query on why the voltmeter circuit would not blow if put on this wire when the dc-dc charger was sucking 60A through that main line? Why doesn't any of that current go up the little voltmeter wire on the way to its destination?
A voltmeter has high impedance and isn't affected by the current directly. You can have 1000 A in that "main line" and any voltmeter will still be able to measure the voltage in any point of the "main line". The current through the voltmeter itself is determined by the _voltage_ between its terminals and the internal resistance of the voltmeter. A typical DC voltmeter has 100 kΩ to 10 MΩ input resistance (cheap meters might have lower and expensive ones higher). You can calculate the current through it using Ohm's law. This is basic fundamental electrical theory. I suggest you read about how voltmeters work.
The above are the basics. High DC currents could induce voltage transients at power-on and power-off. A really cheap voltmeter might have bad protection circuitry and its internals could be damaged due to high voltage spikes. But most DC-DC converters are built to not cause large voltage spikes, or they would also damage other electronic equipment.
Oh you misunderstand me. I am not asking about a handheld meter. I meant this digital voltmeter which I want to add to a circuit.
I am asking why, if I make an extra circuit out of my starter battery to dc charger circuit, why the other circuit would not have the larger amps go through it which I was told it wouldn't earlier.
Forget the voltmeter.
Say there is a main circuit where starter battery connects to dc-dc charger and has 60A current running through it when the charger is running.
I then put any additional circuit, say an LED light for simplicity, on a branch from that circuit, why would the LED light not blow? Would it only take the current it requires? If so why is that? That is what I am asking.
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Oh you misunderstand me. I am not asking about a handheld meter. I meant this digital voltmeter which I want to add to a circuit.
I am asking why, if I make an extra circuit out of my starter battery to dc charger circuit, why the other circuit would not have the larger amps go through it which I was told it wouldn't earlier.
Forget the voltmeter.
Say there is a main circuit where starter battery connects to dc-dc charger and has 60A current running through it when the charger is running.
I then put any additional circuit, say an LED light for simplicity, on a branch from that circuit, why would the LED light not blow? Would it only take the current it requires? If so why is that? That is what I am asking.
Your questions don't make much sense to me. But I'll try.
1. It's not good to put in parallel two batteries of different size. Yes, you could, but you would have to take precautions. But it doesn't sound like you have enough knowledge and it's hard to explain in a forum.
2. Why would 60 A current go to the starter battery? Normally its internal resistance will limit the charge current, unless its completely drained. It would be connected in parallel and current will flow according to the charge voltage applied (again, Ohm's law).
3. A LED light will have a series resistance to limit the current for the appropriate voltage (if it doesn't, you have to calculate and add one). Again, doesn't matter what other currents flow around it, if there is a series resistor calculated for 12V, then the correct amount of current will flow through the LED. Ohm's law, read up on it.
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Oh you misunderstand me. I am not asking about a handheld meter. I meant this digital voltmeter which I want to add to a circuit.
Any voltmeter is connected in the same way, it doesn't matter if it's handheld or a panel meter or whatever. Digital panel meters might require a separate power input, but it can be taken from the same circuit, or from another 12V line, doesn't really matter in a car. The voltage requirement for the power input for digital panel meters vary, but they will typically work down to e.g. 5 V (read the specs), so they will not be affected by the varying voltage of your high current application. Typically digital voltmeters may draw about 10 - 30 mA current to power their internals and the display.
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Oh you misunderstand me. I am not asking about a handheld meter. I meant this digital voltmeter which I want to add to a circuit.
I am asking why, if I make an extra circuit out of my starter battery to dc charger circuit, why the other circuit would not have the larger amps go through it which I was told it wouldn't earlier.
Forget the voltmeter.
Say there is a main circuit where starter battery connects to dc-dc charger and has 60A current running through it when the charger is running.
I then put any additional circuit, say an LED light for simplicity, on a branch from that circuit, why would the LED light not blow? Would it only take the current it requires? If so why is that? That is what I am asking.
Your questions don't make much sense to me. But I'll try.
1. It's not good to put in parallel two batteries of different size. Yes, you could, but you would have to take precautions. But it doesn't sound like you have enough knowledge and it's hard to explain in a forum.
That isn't what I'm doing. The dc-dc charger is designed to be in between the two and that is where it is.
2. Why would 60 A current go to the starter battery? Normally its internal resistance will limit the charge current, unless its completely drained. It would be connected in parallel and current will flow according to the charge voltage applied (again, Ohm's law).
Wrong way around.
The dc-dc charger puts a load request so that the 60A comes from the starter, through the dc-dc charger which then turns it to the appropriate voltage to charge the leisure battery. Look up Sterling power BB1260 if you want to see what device I mean. My idea is to put the voltmeter circuit on this wire run on the starter battery side so I don't have to make new wires through to the engine for the voltmeter.
3. A LED light will have a series resistance to limit the current for the appropriate voltage (if it doesn't, you have to calculate and add one). Again, doesn't matter what other currents flow around it, if there is a series resistor calculated for 12V, then the correct amount of current will flow through the LED. Ohm's law, read up on it.
Thanks, this is all I was really looking for an explanation for as people have mentioned it would be ok but did not explain why.
Also how do I know if a device has series resistance or not? I would imagine a commercial device would have that built in right?
I keep hearing about this Ohm's law. Might be time I take a look at it. ^-^
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Also how do I know if a device has series resistance or not?
If it says it's a LED made for 12V (or for car usage or something like that), then it probably has. Nowadays there are so many applications of Light Emitting Diodes around, so it's hard to know without seeing the actual device.
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You will keep on that now of course to have some more material to argue about.
No, I won't.
I'm not looking to argueing.
I want to make it simple and comprehensive for you.
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I just had the idea to get one of these due to not trusting the intermittent battery light so then I can monitor the actual voltage when driving without having to pop the hood at a layby and check manually when that light is coming on and off.
You need a voltmeter and two bistable multivibrator circuits.
Voltmeter you connect to where ever you have a reasonable long term reference value.
1st bistable you connect to parallel with intermittent untrusted light activator.
2nd bistable you connect to parallel with next connection point away from intermittent untrusted light activator.
Bistable flipping levels you adjust to same level as intermittent untrusted light activator has.
Bistable indicators and resetting you place comfortable.
You operate the triplet so that long term reference you monitor for general out of the intermittent untrusted light situation and bistable indicators for special out of the intermittent untrusted light situation.
Difference between general and special situation goes so that after special situation one or two bistables are indicating a special situation.
If both bistables are indicating you move the 2nd one a connection point further away from the activator.
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If you don't want to tap directly from your car's cigarette lighter power port, take a look at this.
These fuse taps are commonly used when adding a backup camera to an older car.
https://www.youtube.com/watch?v=zm0KRm7jy_g (https://www.youtube.com/watch?v=zm0KRm7jy_g)
Youtube is blocked for me, but the general term is fuse taps?
As was discussed the most straight forward for me will be to route it from the dc-dc charger battery cable circuit. Due to large size difference in wires I am thinking to just wrap the little wire around the terminal post of the battery isolator switch between starter battery positive and dc-dc charger input positive. Also with inline fuse. Sounds ok?
No Youtube in the UK?
From here on, I will just consider you a troll.
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I appreciate that you, the OP, have expressed some concern about the safety of connecting a voltmeter to your car's wiring, especially to circuits that draw high current (like, say, the starter or alternator).
Dunno if this'll help, and this has already been stated by others here, but rest assured:
There's no way you're going to damage any voltmeter--whether it's a high-impedance DMM or just a panel meter--by connecting it to any part of your car's wiring.
No way.
Doesn't matter how much current is flowing through a circuit: the voltmeter itself only draws a tiny amount of current. There's no way that high current can be "forced" into the voltmeter.
The only thing that could harm the voltmeter would be overvoltage, which is not a concern here.
An ammeter is a different story: if you place, say, a DC ammeter rated at 10 amps into your starter circuit and then crank the engine over, you're going to get smoke (or a blown fuse), because all of the current goes through the ammeter (or at least through its shunt resistor).
Not the case with a voltmeter. So go ahead and attach it, and let us know how it works.
Maybe this'll help:
Think about it this way: you can connect a voltmeter--any voltmeter that's rated for that voltage (120 or 240 volts, depending on where you live)--to your house's power wiring, and it won't harm the meter.
The house's wiring is certainly capable of turning any meter into a melted blob almost instantly, and yet it will not. That's because, again, only a tiny amount of current, which the meter is well capable of handling, goes through the meter. (In the case of a DMM it's almost non-measurable, with an input impedance of 10 megohms or so.)
HTH.
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If you don't want to tap directly from your car's cigarette lighter power port, take a look at this.
These fuse taps are commonly used when adding a backup camera to an older car.
https://www.youtube.com/watch?v=zm0KRm7jy_g (https://www.youtube.com/watch?v=zm0KRm7jy_g)
Youtube is blocked for me, but the general term is fuse taps?
As was discussed the most straight forward for me will be to route it from the dc-dc charger battery cable circuit. Due to large size difference in wires I am thinking to just wrap the little wire around the terminal post of the battery isolator switch between starter battery positive and dc-dc charger input positive. Also with inline fuse. Sounds ok?
No Youtube in the UK?
From here on, I will just consider you a troll.
Don't warp what I wrote. I didn't say anything about it not being in the UK. There are plenty of instances where it can be blocked - work or campus setting. So stop trying to push some agenda that I am a troll.
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I appreciate that you, the OP, have expressed some concern about the safety of connecting a voltmeter to your car's wiring, especially to circuits that draw high current (like, say, the starter or alternator).
Dunno if this'll help, and this has already been stated by others here, but rest assured:
There's no way you're going to damage any voltmeter--whether it's a high-impedance DMM or just a panel meter--by connecting it to any part of your car's wiring.
No way.
Doesn't matter how much current is flowing through a circuit: the voltmeter itself only draws a tiny amount of current. There's no way that high current can be "forced" into the voltmeter.
The only thing that could harm the voltmeter would be overvoltage, which is not a concern here.
An ammeter is a different story: if you place, say, a DC ammeter rated at 10 amps into your starter circuit and then crank the engine over, you're going to get smoke (or a blown fuse), because all of the current goes through the ammeter (or at least through its shunt resistor).
Not the case with a voltmeter. So go ahead and attach it, and let us know how it works.
Maybe this'll help:
Think about it this way: you can connect a voltmeter--any voltmeter that's rated for that voltage (120 or 240 volts, depending on where you live)--to your house's power wiring, and it won't harm the meter.
The house's wiring is certainly capable of turning any meter into a melted blob almost instantly, and yet it will not. That's because, again, only a tiny amount of current, which the meter is well capable of handling, goes through the meter. (In the case of a DMM it's almost non-measurable, with an input impedance of 10 megohms or so.)
HTH.
Thank you.
Just the simple facts and no accusations or attacks.
All I had been asking for all this time.
You explained definitively that it won't but could you also add the theory of why it won't? Why doesn't all the extra current flow to it? Is it this Ohm's law again that I keep seeing mentioned? :D
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You explained definitively that it won't but could you also add the theory of why it won't? Why doesn't all the extra current flow to it? Is it this Ohm's law again that I keep seeing mentioned? :D
The simple explanation is this:
A voltmeter is a (relatively) high-impedance device.
If we're talking about DC here (and we are--12 volts DC, nominal, for an automobile)--that means that it has a high resistance.
If we connect that voltmeter across some voltage--in this case, a 12-volt battery (never mind exactly where that happens, at the battery terminals, the cigarette lighter socket or somewhere else)--the voltmeter will only draw as much current as its resistance will allow it to.
So yeah, Ohm's Law covers this.
One of the 3 forms of that law is
I = E/Rmeaning that current equals voltage divided by resistance.
To show just how little current might flow, take the case of a DMM with a 10 megohm impedance. The current in this case will be 12/10,000,000, which is 0.00000012 amps, or 0.12 microamps.
Even a (mechanical) panel meter, which has a much lower resistance, will still draw very little current, in the milliamp range, far too little to harm it.
You cannot force current through a circuit; that circuit will only draw as much current as its resistance (or impedance in the case of AC) will allow it to.
Make sense?
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You explained definitively that it won't but could you also add the theory of why it won't? Why doesn't all the extra current flow to it? Is it this Ohm's law again that I keep seeing mentioned? :D
The simple explanation is this:
A voltmeter is a (relatively) high-impedance device.
If we're talking about DC here (and we are--12 volts DC, nominal, for an automobile)--that means that it has a high resistance.
If we connect that voltmeter across some voltage--in this case, a 12-volt battery (never mind exactly where that happens, at the battery terminals, the cigarette lighter socket or somewhere else)--the voltmeter will only draw as much current as its resistance will allow it to.
So yeah, Ohm's Law covers this.
One of the 3 forms of that law is
I = E/Rmeaning that current equals voltage divided by resistance.
To show just how little current might flow, take the case of a DMM with a 10 megohm impedance. The current in this case will be 12/10,000,000, which is 0.00000012 amps, or 0.12 microamps.
Even a (mechanical) panel meter, which has a much lower resistance, will still draw very little current, in the milliamp range, far too little to harm it.
You cannot force current through a circuit; that circuit will only draw as much current as its resistance (or impedance in the case of AC) will allow it to.
Make sense?
Yes cheers!
I will do some more reading into it now I see the relevance.
This is what the beginner sub should be about but from my little time here it is 90% belittling for not knowing already and trolling.
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Another way to think about this:
Imagine in your house you have 3 lamps that use old-fashioned incandescent light bulbs.
One has a 100-watt bulb in it.
One has a 60-watt bulb in it.
One has a 10-watt bulb in it.
When you plug in any of those lamps, you're connecting the bulb directly across your house's wiring, which in your case is 240 volts.
Why don't those bulbs go poof! when you plug them in? Your house wiring is capable of delivering an enormous amount of current, far more than those bulbs can take, so why don't they just burn out instantly?
Let's look at all 3 bulbs and how much current they use, using the formula for power:
P = V * A
(power in watts equals volts times amps)
We'll rearrange it to find current, since we know power and voltage:
A = P/V
The 100-watt bulb uses 100/240 or 0.416 amps;
The 60-watt bulb uses 60/240 = 0.25 amps;
The 10-watt bulb uses 10/240 or 0.041 amps.
The reason for this is that the higher the power (wattage) of the load, the lower the resistance.
The 100-watt bulb draws 0.416 amps because its resistance is about 577 ohms. It'll never draw more.
The 60-watt bulb draws 0.25 amps because its resistance is about 960 ohms. It'll never draw more.
The 10-watt bulb draws 0.041 amps because its resistance is about 5770 ohms. It'll never draw more.
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Another way to think about this:
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The 10-watt bulb draws 0.041 amps because its resistance is about 5770 ohms. It'll never draw more.
Ok, so high resistance means low current, but why is it that these small devices have high resistance? What makes them like that? Why doesn't a little device have low resistance? I am not saying all small devices must have high resistance but why is it that usually the piddly ones have high resistance?
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Another way to think about this:
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The 10-watt bulb draws 0.041 amps because its resistance is about 5770 ohms. It'll never draw more.
Ok, so high resistance means low current, but why is it that these small devices have high resistance? What makes them like that? Why doesn't a little device have low resistance? I am not saying all small devices must have high resistance but why is it that usually the piddly ones have high resistance?
Hmm; that's a little like asking "why is the sky blue?".
You're asking why some devices have high resistance: I guess the answer is ... because.
Do you mean small as in physically small?
A physically small resistor, like the one shown here, can have a resistance ranging from less than 1 ohm up to 10s of megohms, so physical size has nothing to do with it.
(https://buildyourcnc.com/cdn/shop/files/IMG_9501-800.jpg?v=1730085446&width=493)
A DMM has extremely high impedance (which is kinda-sorta the same thing as resistance but not really, but we can treat it the same in this discussion) because it uses electronic amplifiers inside, called opamps, which have extremely high input impedance, and therefore draw very little current.
Other than that, not sure what "piddly" devices you're referring to.
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Another way to think about this:
...
The 10-watt bulb draws 0.041 amps because its resistance is about 5770 ohms. It'll never draw more.
Ok, so high resistance means low current, but why is it that these small devices have high resistance? What makes them like that? Why doesn't a little device have low resistance? I am not saying all small devices must have high resistance but why is it that usually the piddly ones have high resistance?
Hmm; that's a little like asking "why is the sky blue?".
You're asking why some devices have high resistance: I guess the answer is ... because.
Do you mean small as in physically small?
A physically small resistor, like the one shown here, can have a resistance ranging from less than 1 ohm up to 10s of megohms, so physical size has nothing to do with it.
(https://buildyourcnc.com/cdn/shop/files/IMG_9501-800.jpg?v=1730085446&width=493)
A DMM has extremely high impedance (which is kinda-sorta the same thing as resistance but not really, but we can treat it the same in this discussion) because it uses electronic amplifiers inside, called opamps, which have extremely high input impedance, and therefore draw very little current.
Other than that, not sure what "piddly" devices you're referring to.
I just mean that in general if you buy a cheap little device like an LED light or a voltmeter in this case or any of those little appliances you know they are going to have a low current draw, so I am asking why is that? Small and cheap usually means low current. I mention cheap because I imagine there are exceptions of microelectronics with very high current or things like that so cheap is added to explain I only mean the common every day little items you will find on sale in shops.
Is it something to do with physics where the air is causing high resistance or something and the very little physical space taken up by the appliance cannot contain much of normal low cost raw materials that would give it a high current/low resistance?
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Wellll, let's look at "every day little items you will find on sale in shops" and classify them as to current draw:
- Anything that generates heat: moderate to high current (it takes power to generate heat from electricity)
- Little LED thingies like keychain lights, toys, etc.: very low current, since single non-super-bright LEDs draw very little current (typically about 20mA)
- Anything with a motor, like a fan, rotisserie motor, etc.: moderate current draw (motors have magnetic windings to drive them)
- Small audio products with speakers (not just headphones): moderate current, as it takes moderate power (say 1/2 watt to maybe 2-3 watts) to produce loud enough sound.
- Higher-powered audio things (like home-entertainment receivers): moderate to mid-high current.
Does that help any? Things that run on AA batteries and only display stuff on an LCD screen use very little power; things that do work like produce heat, move high volumes of air, saw through a 2x4 or produce very loud audio require more power, hence higher current.
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Does that help any? Things that run on AA batteries and only display stuff on an LCD screen use very little power; things that do work like produce heat, move high volumes of air, saw through a 2x4 or produce very loud audio require more power, hence higher current.
Well you actually just made a list of things with varying currents not why. Those other things you mention like hi-fi systems I no longer class as 'piddly'.
I just mean the tiny tacky stuff like LED lights and things with physical properties no larger hand your hand probably. I don't get why they almost necessarily have low current. I am not sure how to ask it but is it by design of the manufacturer or the natural laws of nature that something so small, without using some super rare material, will be low current?
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Does that help any? Things that run on AA batteries and only display stuff on an LCD screen use very little power; things that do work like produce heat, move high volumes of air, saw through a 2x4 or produce very loud audio require more power, hence higher current.
Well you actually just made a list of things with varying currents not why. Those other things you mention like hi-fi systems I no longer class as 'piddly'.
I just mean the tiny tacky stuff like LED lights and things with physical properties no larger hand your hand probably. I don't get why they almost necessarily have low current. I am not sure how to ask it but is it by design of the manufacturer or the natural laws of nature that something so small, without using some super rare material, will be low current?
Well, it's getting harder to answer your questions as they're getting pretty abstract, but I'll play along a little bit more:
It depends on what the thing does.
Does it produce heat? like enough to toast a piece of bread, dry your hair, microwave something? Lots of power (and therefore current).
Does it just light up a piddly little LED (flashlight), or show something on a little LCD display (thermometer, digital clock)? Very very little power; those things consume almost no power. My clock that runs on a single AA cell has run for more than 2 years now on the same battery.
Doing things like moving stuff (fans, drills, saws, etc.) takes a fair amount of energy, hence higher current.
Things like DMMs, where most of the device consists of microelectronics (chips) that drive a very low-power LCD display use very little current; semiconductors (transistors, diodes, MOSFETs) on a microscopic scale just inherently use very little power (and that's at least partly because they are physically small).
If you keep asking "why?", I'm afraid that's more of a metaphysical question that I really can't answer.
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Does that help any? Things that run on AA batteries and only display stuff on an LCD screen use very little power; things that do work like produce heat, move high volumes of air, saw through a 2x4 or produce very loud audio require more power, hence higher current.
Well you actually just made a list of things with varying currents not why. Those other things you mention like hi-fi systems I no longer class as 'piddly'.
I just mean the tiny tacky stuff like LED lights and things with physical properties no larger hand your hand probably. I don't get why they almost necessarily have low current. I am not sure how to ask it but is it by design of the manufacturer or the natural laws of nature that something so small, without using some super rare material, will be low current?
Well, it's getting harder to answer your questions as they're getting pretty abstract, but I'll play along a little bit more:
It depends on what the thing does.
Does it produce heat? like enough to toast a piece of bread, dry your hair, microwave something? Lots of power (and therefore current).
Does it just light up a piddly little LED (flashlight), or show something on a little LCD display (thermometer, digital clock)? Very very little power; those things consume almost no power. My clock that runs on a single AA cell has run for more than 2 years now on the same battery.
Doing things like moving stuff (fans, drills, saws, etc.) takes a fair amount of energy, hence higher current.
Things like DMMs, where most of the device consists of microelectronics (chips) that drive a very low-power LCD display use very little current; semiconductors (transistors, diodes, MOSFETs) on a microscopic scale just inherently use very little power (and that's at least partly because they are physically small).
If you keep asking "why?", I'm afraid that's more of a metaphysical question that I really can't answer.
Ok yes I think I get the gist now, thanks.
The components would be chosen by the manufacturer to do the specific job and whether it is low or high current is incidental to its intended purpose.
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The components would be chosen by the manufacturer to do the specific job and whether it is low or high current is incidental to its intended purpose.
Not completely incidental. Electricity costs money and demands infrastructure, and its annoying and costly to charge and change batteries. So throughout every technology field, there is an incentive to make devices use less power and draw less current (there are even laws about this). Or when certain power is really needed, use it in a more efficient way (waste less as heat, less friction, use heat pumps etc.). A practical example in electronics is big, clumsy transformers that have been replaced with SMPS (switch mode power supplies) that use smaller components, but can deliver power at a much higher efficiency (less electricity wasted as heat).
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The components would be chosen by the manufacturer to do the specific job and whether it is low or high current is incidental to its intended purpose.
Not completely incidental. Electricity costs money and demands infrastructure, and its annoying and costly to charge and change batteries. So throughout every technology field, there is an incentive to make devices use less power and draw less current (there are even laws about this). Or when certain power is really needed, use it in a more efficient way (waste less as heat, less friction, use heat pumps etc.). A practical example in electronics is big, clumsy transformers that have been replaced with SMPS (switch mode power supplies) that use smaller components, but can deliver power at a much higher efficiency (less electricity wasted as heat).
Yes I get your point, but it is different to what I wrote.
Sure I agree the companies will seek more efficient components when they are available. My comment though was that if they want to make an induction cooker for example which I do takes loads of power then their goal will not be let's make it efficient power wise. That might be a second or third goal but the number one goal is make an induction cooker. :)
Anyway that is splitting hairs. I get your point.
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Just the simple facts and no accusations or attacks.
Maybe you have missed a lot of the replies, but there have been many that have presented the facts without accusations or attacks. Not to take anything away from Analog Kid, but he's not the only one. In fact I applaud he persistence.
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Voltmeter is fine idea. I paid attention when you mentioned a DC to DC converter, as that presents a load to the 12V system. Maybe your trouble light indicates that the inverter load is too high ? Or other speculation maybe related, to having that inverter (??).
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Just the simple facts and no accusations or attacks.
Maybe you have missed a lot of the replies, but there have been many that have presented the facts without accusations or attacks. Not to take anything away from Analog Kid, but he's not the only one. In fact I applaud he persistence.
Well it is a case of that people will generally focus on the negative.
Yes I am not saying there were not others as well, but they were mixed up in the heat of battle. Now things have settled Analog Kid's posts shine like a beacon.
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Voltmeter is fine idea. I paid attention when you mentioned a DC to DC converter, as that presents a load to the 12V system. Maybe your trouble light indicates that the inverter load is too high ? Or other speculation maybe related, to having that inverter (??).
Thanks, it is a logical assertion going only from what I wrote however I was using it for a few months already without this issue arising. The light only started coming on consistently recently out of nowhere, which is why it has me stumped. If it happened soon after having installed a new part it would be easier to diagnose that as the likely culprit but it apparently comes out of the blue which is why I have had a hard time finding the root cause.
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Keep in mind that alternator can't or shouldn't cook the battery, for that you need an external charger.
So initial battery voltage can be higher than what it is after regular use of long enough.
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Voltmeter is fine idea. I paid attention when you mentioned a DC to DC converter, as that presents a load to the 12V system. Maybe your trouble light indicates that the inverter load is too high ? Or other speculation maybe related, to having that inverter (??).
Thanks, it is a logical assertion going only from what I wrote however I was using it for a few months already without this issue arising. The light only started coming on consistently recently out of nowhere, which is why it has me stumped. If it happened soon after having installed a new part it would be easier to diagnose that as the likely culprit but it apparently comes out of the blue which is why I have had a hard time finding the root cause.
So a meter is a good idea but I would just do the cigarette lighter and a DMM. It's not worth to wire and mount a panel meter in the van for troubleshooting purpose. Once you have the problem fixed you don't want the meter there do you?
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Keep in mind that alternator can't or shouldn't cook the battery, for that you need an external charger.
So initial battery voltage can be higher than what it is after regular use of long enough.
No idea what you mean here but I know that the setup is correct according to the dc charger install specifications.
Alternators do fail. It was old. The mechanic who looked at it said they can fail any time. Adding the charger would have put a massive load on an older alternator so makes sense why it would cause it to fail.
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Voltmeter is fine idea. I paid attention when you mentioned a DC to DC converter, as that presents a load to the 12V system. Maybe your trouble light indicates that the inverter load is too high ? Or other speculation maybe related, to having that inverter (??).
Thanks, it is a logical assertion going only from what I wrote however I was using it for a few months already without this issue arising. The light only started coming on consistently recently out of nowhere, which is why it has me stumped. If it happened soon after having installed a new part it would be easier to diagnose that as the likely culprit but it apparently comes out of the blue which is why I have had a hard time finding the root cause.
So a meter is a good idea but I would just do the cigarette lighter and a DMM. It's not worth to wire and mount a panel meter in the van for troubleshooting purpose. Once you have the problem fixed you don't want the meter there do you?
Yes I will always want it or I would have gotten the lighter port one instead.
It was discussed by some other users here they used to be mounted as standard on vehicles on the dashboard until they went out of fashion.
It is always useful to know and see that the voltage goes up when the engine starts. Do you not want a rev counter or speedometer just because there is no malfunction?
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The problem with a panel meter that most of them today are digital and you need power for them to work. So you need the ingition switch to both turn off the power to the meter as well as the power it measures otherwise you may drain your battery.
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The problem with a panel meter that most of them today are digital and you need power for them to work. So you need the ingition switch to both turn off the power to the meter as well as the power it measures otherwise you may drain your battery.
Ye I get that but I have some spare switches I will just use one of those but someone else also mentioned that elsewhere and it reminded me I had been thinking about adding a starter battery disconnect anyway at some point because as I live in my van the parasitic drain of opening and closing and central locking and whatever else wastes the battery too.
Been looking up disconnects and saw there are even remote control ones which look appealing so then I won't have to open the hood every single time. One big drawback I saw mentioned in reviews was that you could actually trigger it while driving which could cause serious damage to components. If it was on your keyring in your pocket I could see that happening very easily! However would not be too hard to avoid just putting it somewhere like in one of the shelves around the driver's area and could also take the battery out as still easier than going in to the hood each time.
I only drive once a week average and I have checked the battery before setting off before and looking at my notes it uses about 40-50% through the week while stationary. Haven't had any issue starting it so far but seems a horrible waste of battery charge on useless power draining components.
Do you techies have any better ideas to failsafe the remote disconnect beyond what I have suggested above?
It isn't such a big deal to open the hood each time once per week with a manual one when I park. Less to go wrong in this case.
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I wouldn't go for remote disconnect because the remote control circuit need constant power to work so another thing to drain your valuable power. Do everything manually. You have to run long wires but you can have the switch inside the van. However, if I were you and I only use the van once a week I would leave the large disconnect in the engine compartment and manual switch it on when I want to use the van. Once a week isn't all that much work.
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I wouldn't go for remote disconnect because the remote control circuit need constant power to work so another thing to drain your valuable power. Do everything manually. You have to run long wires but you can have the switch inside the van. However, if I were you and I only use the van once a week I would leave the large disconnect in the engine compartment and manual switch it on when I want to use the van. Once a week isn't all that much work.
It very difficult to lift the lid brother. I need to lay down after. :-DD
Btw I was just looking up low voltage disconnects for my leisure battery when I saw some lower price ones built on arduino or whatever smp thing and it looks like those could be used to disconnect the voltmeter once the engine stops. No way I am tapping the ignition line just for this and would be another cheap option if I am understanding those devices correctly. Looking at the reviews indeed it does look like people are using it for similar purposes:
https://www.amazon.co.uk/Battery-Voltage-Disconnect-XH-M609-Protection/dp/B08BCMH1FY (https://www.amazon.co.uk/Battery-Voltage-Disconnect-XH-M609-Protection/dp/B08BCMH1FY)
I could set it to shutoff below 13v as that would be when the alternator was off, and of course when the engine is off too.
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Keep in mind that alternator can't or shouldn't cook the battery, for that you need an external charger.
So initial battery voltage can be higher than what it is after regular use of long enough.
No idea what you mean here but I know that the setup is correct according to the dc charger install specifications.
Alternators do fail. It was old. The mechanic who looked at it said they can fail any time. Adding the charger would have put a massive load on an older alternator so makes sense why it would cause it to fail.
It means that battery voltage is not very stable definition.
Like a rest voltage and charge voltage where before charging the voltage is lower, but higher voltage is still not charging.
Cooking means that old lead acid battery was fully loaded after few days of caps open, over a boiling point charge voltage and water added when needed.
Your intermittent problem can be anything along the route of electricity.
It also has a general and special problem situations.
General situation is that you have a situation.
Special situation is that you try to pinpoint it.
Old cars have old fixes.
One of mine was a wire between intake manifold and engine block.
The wire had a voltage, but other way was completely unknown and one spot of plastic was melted away.
That exposed spot was also intermittently shorting to block and killing something vital.
Repair was a new insulation from a cut open wire guide tube.
Pinpointing the problem can be very difficult.
If it is intermittently disconnecting spot you can possibly fix it by adding a ring source.
Means that you add a wire from the beginning to the end.
But finally, if not a wire itself, all connections are away from that ring, somewhere is a T-junction.
If it is an overloading spot you need means to record that short moment of the happening.
You also need at least one control spot where the overloading happens a bit later or not at all.
Third possibility is that you swap parts and finally have a gained trust that the problem is gone.
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I wouldn't go for remote disconnect because the remote control circuit need constant power to work so another thing to drain your valuable power. Do everything manually. You have to run long wires but you can have the switch inside the van. However, if I were you and I only use the van once a week I would leave the large disconnect in the engine compartment and manual switch it on when I want to use the van. Once a week isn't all that much work.
It very difficult to lift the lid brother. I need to lay down after. :-DD
Btw I was just looking up low voltage disconnects for my leisure battery when I saw some lower price ones built on arduino or whatever smp thing and it looks like those could be used to disconnect the voltmeter once the engine stops. No way I am tapping the ignition line just for this and would be another cheap option if I am understanding those devices correctly. Looking at the reviews indeed it does look like people are using it for similar purposes:
https://www.amazon.co.uk/Battery-Voltage-Disconnect-XH-M609-Protection/dp/B08BCMH1FY (https://www.amazon.co.uk/Battery-Voltage-Disconnect-XH-M609-Protection/dp/B08BCMH1FY)
I could set it to shutoff below 13v as that would be when the alternator was off, and of course when the engine is off too.
The best setup I did was some years back when I owned a Volvo. It had a problem with charging the battery with low automobile use.
I used a 18 gauge wire pair from the battery to the inside cabin compartment, with fuse right at the positive battery terminal. I ran it though the firewall which was no easy task on that vehicle. I used a terminal block so I could use the battery for power as well as charging with a solar panel system.
It was easy to measure the voltage that way inside the car, and I designed a system to measure the voltage once every 10 minutes and transmit that reading to a receiver in the house. The computer (Windows) monitored the receiver and kept a log of all the voltage readings. Over time I got a good idea what the battery and charging system was doing as well as not doing. That led to the solar panel system which took care of all that. Then I could leave the car sit for weeks and not worry about the battery running down.
It was pretty cool getting voltage readings 24 hour a day 7 days a week. That gives you a lot of history data to work with.
The measurement system has to draw very little current from the battery however so it does not contribute much to the battery drain, unless of course you pair that with a solar charger system.
When I worked in the industry I worked in the power control field, so none of this was really that new to me. I do realize that there are nuances to some of this that require close attention and careful and concise explanations. First and foremost, we have to be able to understand each other as well as possible or else it leads to a lot of misunderstandings and back and forth text posts which can take days in forums like this. Patience is mandatory.
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As an alternative to this, to give the OP ideas maybe.
As soon as the engine starts all you will see on the voltmeter is the output voltage of your alternator/regulator. Around 14.40V.
If your battery is 25 years old and only has 2% capacity remaining, it will still show as 14.40V
The project I have never started was to place a small very low powered circuit that monitors the battery for "dips" in voltage. Like when you start the car.
So when you start the car the MCU is woken and begins datalogging the voltage into RAM. When the voltage returns high or goes up to 14.40V the MCU then provides the "Min Battery Voltage" to a BT app.
There are a lot of "ifs and buts" and unsolved questions, but the idea was that everytime you start the car it records the minimum battery voltage. You don't need to look if you don't want, if the minimum crank voltage drops below a level like 9V it will notify you that your battery may be weak and consider a replacement before winter.
It is in fairness a long way to just "listen", the count of cranks, the pitch of the motor, the "readiness" and "eagerness" to start from a fresh battery is very obvious. The downside is, the only time you notice is when you put a new battery in.
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As an alternative to this, to give the OP ideas maybe.
As soon as the engine starts all you will see on the voltmeter is the output voltage of your alternator/regulator. Around 14.40V.
If your battery is 25 years old and only has 2% capacity remaining, it will still show as 14.40V
The project I have never started was to place a small very low powered circuit that monitors the battery for "dips" in voltage. Like when you start the car.
So when you start the car the MCU is woken and begins datalogging the voltage into RAM. When the voltage returns high or goes up to 14.40V the MCU then provides the "Min Battery Voltage" to a BT app.
There are a lot of "ifs and buts" and unsolved questions, but the idea was that everytime you start the car it records the minimum battery voltage. You don't need to look if you don't want, if the minimum crank voltage drops below a level like 9V it will notify you that your battery may be weak and consider a replacement before winter.
It is in fairness a long way to just "listen", the count of cranks, the pitch of the motor, the "readiness" and "eagerness" to start from a fresh battery is very obvious. The downside is, the only time you notice is when you put a new battery in.
Didn't really understand that but the battery is new anyway. Within a year old.
The battery was another thing that died when I added the dc-dc charger. :-DD I know you guys will say it was my bad setup but I already knew the battery was weak and in need of replacement because it would struggle to start after being left parked for just a week. It finally totally conked out about the same time as the alternator and would no longer accept charge.
The new one is working nicely. No problems starting through winter. The old one would hardly be able to crank. Just a few chugs and give up if not careful about leaving it for too long but the new one on some cold days I recall it would crank happily for near to 5+ seconds before starting up the engine.
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Just to re-iterate what I think is a simple solution for OP.
1. Get a USB tap with voltage monitor.
A link for typical is
https://www.googleadservices.com/pagead/aclk?sa=L&ai=DChsSEwjJ2tLVw86OAxVpF60GHXRhG7UYACICCAEQAxoCcHY&co=1&ase=2&gclid=Cj0KCQjwyvfDBhDYARIsAItzbZGnEwWlFaOZgD_IAeX9i02FM680rVsNUG4lWBIjSC3RaIvEwHPga0EaAr10EALw_wcB&ohost=www.google.com&cid=CAESeOD29Mc41Jep0n25TZGwVUMSIBd83TF5sbWHETNnSuoJQiIvGrkgjDW9TJ7QT3C8MkBdrWhXrCHA_2c6qfd-vqOFGS4MJZFA5p4yQQUjQ5bwy-HRxXocbn1PmdOlXafuI1l7uWB9UYjduGzcLF-x0K-sP9H6cgSVlw&category=acrcp_v1_41&sig=AOD64_1jL2_TYzHZUFopoh9p4GFRzD2gMw&ctype=5&q=&nis=4&ved=2ahUKEwj5iM7Vw86OAxVzBjQIHXF0HSgQ9aACKAB6BAgFEBw&adurl= (https://www.googleadservices.com/pagead/aclk?sa=L&ai=DChsSEwjJ2tLVw86OAxVpF60GHXRhG7UYACICCAEQAxoCcHY&co=1&ase=2&gclid=Cj0KCQjwyvfDBhDYARIsAItzbZGnEwWlFaOZgD_IAeX9i02FM680rVsNUG4lWBIjSC3RaIvEwHPga0EaAr10EALw_wcB&ohost=www.google.com&cid=CAESeOD29Mc41Jep0n25TZGwVUMSIBd83TF5sbWHETNnSuoJQiIvGrkgjDW9TJ7QT3C8MkBdrWhXrCHA_2c6qfd-vqOFGS4MJZFA5p4yQQUjQ5bwy-HRxXocbn1PmdOlXafuI1l7uWB9UYjduGzcLF-x0K-sP9H6cgSVlw&category=acrcp_v1_41&sig=AOD64_1jL2_TYzHZUFopoh9p4GFRzD2gMw&ctype=5&q=&nis=4&ved=2ahUKEwj5iM7Vw86OAxVzBjQIHXF0HSgQ9aACKAB6BAgFEBw&adurl=)
This one has a power switch incorporated so you can assure yourself that the parasitic load is not a problem.
2. Mount same. Lots of options here, all dependent on the specific vehicle. Some have plugs in the dash for installing options on high end vehicles that aren't in yours. Some have blank dash space or space on the console. A step drill is your friend here. If nothing of that type presents buy or fabricate an L bracket which can screw to the bottom of the dash or other appropriate location.
3. Get a schematic for your vehicle. It will show which circuits are switched and unswitched by the ignition. I personally would go for a switched circuit to so as to have no worries about parasitic loads, but it is your vehicle and your choice. With this information you can easily access the appropriate circuit at the fuse block with the fuse taps mentioned before. If you actually use the USB charging port you will need to think about a circuit that is designed for enough current that this added load won't be an issue, but on most cars virtually all will be suitable. Just don't use one that has a 3 amp or possibly a 5 amp fuse. Note that if you can't find a schematic you can make a good choice based on the names and purposes of the fuses in the fuse block.
4. Start monitoring. The voltmeter in these taps is not laboratory grade, not calibrated, only one decimal point resolution, but in my experience they are fairly accurate and you are much more interested in changes than in the absolute voltage.
Anyway, good luck to you with your project.