Author Topic: Is there a way to safely charge a car battery with this equipment? If not, why?  (Read 1470 times)

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Offline epigramx

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I have a step-up module from the china shops on which I can adjust both the current(limit) and the voltage output and I can feed it with an old PC PSU's 12V (they're supposedly max 400W, both the module and PSU). Now, I wonder how can I figure out only with that equipment and a particular car battery and a multimeter(I also have a voltage + current monitoring device) how to charge it safely (under supervision). Say, can I just set the module to 14.4V and the current limit to something high-ish and then monitor if the current it draws is dropping, or is there another way (if there is even a way)?
« Last Edit: October 20, 2019, 09:32:52 am by epigramx »
 

Online Yansi

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Re: What's the safest way to "ghetto"-charge a car battery?
« Reply #1 on: October 20, 2019, 09:18:15 am »
Use a proper charger.
 

Offline Simon

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Re: Is there a way to safely charge a car battery with this equipment?
« Reply #2 on: October 20, 2019, 09:32:50 am »
If you want to charge a battery right up 14.4V but don't leave it too long. You can float charge at around 13.5V. i would not try to put 400W or nearly 40A into a typical 40A car battery. i think the charge rate is usually arout 5-10A.

as suggested how about a comercial charger? they would be as cheap as the whole combo you have.
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Offline epigramx

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Re: Is there a way to safely charge a car battery with this equipment?
« Reply #3 on: October 20, 2019, 09:37:49 am »
If you want to charge a battery right up 14.4V but don't leave it too long. You can float charge at around 13.5V. i would not try to put 400W or nearly 40A into a typical 40A car battery. i think the charge rate is usually arout 5-10A.

as suggested how about a comercial charger? they would be as cheap as the whole combo you have.
It's also for the lols because I kept one that is not dead yet, and for general interest about the technology of battery charging (I don't need it for anything particular yet, so it's mainly general research, if it was for a real project, I'd probably try to find an always-on charging system anyway).
So you seem to imply that the voltage of the battery will remain less than 14.4V if I feed it with a 14.4V input (unless I misunderstood) and at that point it can be considered full (or, it sounds more logical to me that the voltage will/should remain 14.4V (if the source can manage it) but the current will drop below what is first drawn).
Regarding the current limit, I would never use the max of that module anyway (I doubt it can survive itself that way), so I guess it would help to research what current that battery model usually draws (unless 5-10A you mentioned is universally true).
« Last Edit: October 20, 2019, 09:40:43 am by epigramx »
 

Online Yansi

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I do not think that you car alternator, let alone in cars equipped with start/stop system cares about your 5-10A charging limit, bhaha!
 

Offline Simon

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if you apply 14.4V the battery will charge to that voltage. once you remove a car battery from charging it will drop the valtage. A sitting battery with nothing connected will be at 12.6V when fully charged. the extra voltage you apply when charging is to make it charge. In a vehicle the battery is held at 13.5V
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Offline Simon

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I do not think that you car alternator, let alone in cars equipped with start/stop system cares about your 5-10A charging limit, bhaha!

that is for a manual charge. that is why the car alternator runs 13.5V not 14.4V
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Online Yansi

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The thing is, alternator is not set for 13.5V.   Be pretty sure it can output over 14V.
 

Offline Simon

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It can output anything within the limits of the magnetics and regulator. Probably easily 28V.....
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Online Yansi

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No, you don't understand, nor know.

Car alternator output is usually set to about 14.4V. There is no point in charging using 13.5 or 13.8V. That would take for ages to charge the battery.

You 5-10A charging current limit  is just a silly talking. Alternator is like "zero fucks given" to your current limits.
 

Offline Simon

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No, you don't understand, nor know.

Car alternator output is usually set to about 14.4V. There is no point in charging using 13.5 or 13.8V. That would take for ages to charge the battery.

You 5-10A charging current limit  is just a silly talking. Alternator is like "zero fucks given" to your current limits.

why does the alternator need to charge the battery that much? the battery is only used to start the engine and if the power demand is in excess of the alternator. The alternator will have a current limit but that is not what controls the battery charging it is to protect the alternator. The charge is controlled with the voltage and hene it is NOT 14.4V, go and measure your own vehicle if you don't beleive me!
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Online Yansi

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Why not you go first then?

 

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Offline Simon

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i did! i recently measure the output of a bus! even though it has a ot to drive the alternator is set at 27V or 13.5V per battery. Same for a tank i measured the supply voltage on: 27V / 2 - 13.5V last time I measured my car: 13.5 to 13.8V.
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Online T3sl4co1l

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FYI, last time I went through this (floating my car battery to top it up) I set it to 14.3V and went from about 20A initially down to a few 100 mA after 24 hours.  This is a little high for a proper (always-on) float, but fine for this duration, and as you can see there was very little if any overcharging.

Electrolysis starts at higher voltages; you can't really charge much faster (than whatever the peak rate is, C/2 or thereabouts?) because the plates load up with bubbles, greatly increasing resistance.  Dangerous, anyway (H2+O2).

OCV is around 13V and the extra voltage is required for charging, to overcome the overpotential of the electrode materials.  Basically the overpotential consumes charge efficiency: you have to charge so-and-so above the electrochemical potential to make anything happen, and the difference is lost as heat.

Which is what makes lithium ion so amazing, there's essentially no overpotential and the cell voltage is entirely due to concentration of ions in the electrodes.  So the charge and discharge efficiency is super high, it looks like a crummy nonlinear capacitor more than a cell.

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Online RoGeorge

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Say, can I just set the module to 14.4V and the current limit to something high-ish and then monitor if the current it draws is dropping, or is there another way (if there is even a way)?

Yes, it's possible, but you must:

- put a series diode in series with the battery (a high current diode, I put a double diode in parallel).  This is a must, because if there is a power outage, then the battery will start pumping current back into the PSU.  Depending on the PSU model, pumping current into the PSU might be dangerous or not, but better safe than sorry.  Put a series diode.

- limit the current, e.g. for the first few hours put a car light bulb in series with the battery.  After the battery voltage is 12-13V, the light bulb can be removed, but keep the protection diode in series with the battery.

- the 14.4V top charging voltage (measured on the battery) depends with battery temperature, I am using this table:
Code: [Select]
Lead Acid generic specs
-----------------------
At a comfortable temperature of 20°C (68°F), gassing starts at charge voltage of 2.415V/cell. When going to –20°C (0°F), the gassing threshold rises to 2.97V/cell.

Battery status -40°C (-40°F) -20°C (-4°F) 0°C (32°F) 25°C (77°F) 40°C (104°F)
Voltage limit on recharge 17.1 16.2 15.3 14.7 14.1
Float voltage at full charge 15.3 14.7 14.1 13.8 13.5
or lower or lower or lower or lower or lower

gasing at 20*C for V >= 14.4V
nominal, no load = 12.6V
floating charge = 13.5...13.8V

- do not let it unsupervised, and be careful with wiring, because a car battery can easily melt very thick wires and start a fire when short-circuited.

Later edit:
https://www.eevblog.com/forum/chat/charging-my-car-battery/
« Last Edit: October 20, 2019, 11:28:10 am by RoGeorge »
 

Offline BradC

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why does the alternator need to charge the battery that much? the battery is only used to start the engine and if the power demand is in excess of the alternator. The alternator will have a current limit but that is not what controls the battery charging it is to protect the alternator. The charge is controlled with the voltage and hene it is NOT 14.4V, go and measure your own vehicle if you don't beleive me!

Well, that was interesting. My 1989 Volvo setpoint at 21 degrees C is 14.3V. My 2008 Landrover starts with a setpoint from the ECU of at 15.3V! (real voltage from the alternator while putting 80A into the battery ~14V) and tapers back to 13.8 once the battery hits > 14.2V. A pair of Volvo TAMD70B diesels are set to 28.6V (14.3/battery) at 21C. Our Volkswagen Golf V (2005) starts at 14.4 and winds back to 13.9 once up to temperature (after 30 mins driving).

Calcium based batteries can be charged extremely hard. The alternator in the Landrover can put 80A into the battery after a particularly cold and hard start and the battery just laps it up until the charge current tapers off before the ECU turns the voltage down.

So there you go. Real data from 3 vehicles and a vessel. Initial charging current on all of the batteries is > 50A. The Landrover is particularly brutal but it's also a pretty big battery.
 

Offline mikerj

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why does the alternator need to charge the battery that much? the battery is only used to start the engine and if the power demand is in excess of the alternator. The alternator will have a current limit but that is not what controls the battery charging it is to protect the alternator. The charge is controlled with the voltage and hene it is NOT 14.4V, go and measure your own vehicle if you don't beleive me!

Pretty much all modern cars will regulate charging voltage to 14.2-14.5v, and even higher than this on start/stop equipped vehicles that use AGM batteries.
 

Offline Simon

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what vehicles use AGM batteries?
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Offline helius

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what vehicles use AGM batteries?
Motorcycles and scooters.
 

Offline Simon

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Wel they tend to be lower capacity so it's more vital to charge them up ready for the next start. I recently charged a collegue motorbike bttery after he left the lights on.
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Online Yansi

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AGM or not, chemistry is the same, voltage is the same.

AGM is just Absorbed Glass Mat, meaning the acid solution is wicked into a woven glass fiber rag, so it does not splash and you get a freedom in orienting of the battery in space whichever way you want.

 

Offline Simon

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Well you charge you batteries as you damn well please then  :horse:
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Online Yansi

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It is fun to watch you being angered when confronted with the truth.
 
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Offline Simon

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I'm not angry. I supplied my information above. i recently worked on a bus with a flat battery because of the electrical load we were putting on it. The alternators (yes 2 of them) were struggling at idle speeds and the battery voltage slowly fell. When I asked for the engine to be reved up hard the voltage spiked at 27.2V and immediately (millisecconds) settled at 27V despite the flat battery and load on the system. It could have gone higher but would not. This is a comercial vehicle. I think they know what they are doing........ You may have any opinion you like.....
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Online Yansi

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Guess what: 27V just tells you those alternators are probably shot, as with 27V (13.5V) you are NOT going to charge the battery, especially during the typical couple of hours of motor run time. Understood?  :-//
 

Offline Simon

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Online T3sl4co1l

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Ah, well there you have it, I left the lights on last night :-DD so I've got it indoors charging right now. Taking a good 12.3A at 13.63V right now, slowly rising (max 14.20).  Was about 12V OC, should be here most of the afternoon then I'll put it back good as new.

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Offline Simon

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shhhh don't tell Yansi you can charge with less than 14V, you will be on his naughty list too...
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Online T3sl4co1l

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Well, so what? It's taking current at a lower voltage because it's in a discharged state.  As the concentration of Pb-->PbO2 and PbSO4-->Pb rises, the cell potential also rises.  (In fact it's up to 13.74V already.)  When all surfaces are fully charged, the voltage levels off somewhere around there (when under some degree of charge, because again, overpotential).  I'm going to float it at 14.2 for a while (preferably 12-24 hr, not sure if I'll get that much time on it tonight) to ensure a full charge (desulfation, to the extent that it can be performed at all).

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Offline Simon

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Yea, and all a battery does these days is start an engine which takes less than 50Wh and is quikly replenished.
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Offline Nusa

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Yea, and all a battery does these days is start an engine which takes less than 50Wh and is quikly replenished.

Under ideal conditions, perhaps. It also has to be able to start a cold engine in adverse conditions. Try it at -18C. 60% of the battery capacity is gone because it's cold. The oil in the engine is a cold thick fluid, so every moving part takes way more energy to move. In fact, that's so important that those are the conditions car batteries are rated under. The CCA (cold cranking amps) is how much current a very cold charged battery should be able to deliver for up to 30 seconds. When it's new.

Now try it at -40C. Yes, I've really had to start vehicles at those temperatures. Better to stay inside if it's not important, to tell the truth. People who deal with such climates regularly have engine and battery heaters. And replace batteries much sooner than those in warm climates.
« Last Edit: October 20, 2019, 11:29:14 pm by Nusa »
 
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Online T3sl4co1l

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Heh, speaking of low car batteries and even lower temperatures -- last year we got some -20 days, one of which I had to go to work on.  Well, car wouldn't start the night before anyway, so I took the battery inside and floated it.  Next morning put it back in, I guarantee you my room temperature, fully charged battery gave me the easiest start of anyone in the whole city that morning.  It didn't seem to bog down from the cold oil at all. ;D

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Offline Simon

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Yea, and all a battery does these days is start an engine which takes less than 50Wh and is quikly replenished.

Under ideal conditions, perhaps. It also has to be able to start a cold engine in adverse conditions. Try it at -18C. 60% of the battery capacity is gone because it's cold. The oil in the engine is a cold thick fluid, so every moving part takes way more energy to move. In fact, that's so important that those are the conditions car batteries are rated under. The CCA (cold cranking amps) is how much current a very cold charged battery should be able to deliver for up to 30 seconds. When it's new.

Now try it at -40C. Yes, I've really had to start vehicles at those temperatures. Better to stay inside if it's not important, to tell the truth. People who deal with such climates regularly have engine and battery heaters. And replace batteries much sooner than those in warm climates.

In which case as Tim mentioned above the battery still charges at less than 14V. I think if a military vehicle can use 27-27.6V (13.5V-13.8V) despite having fuel fired battery and engine heaters for when it's really cold  then that's about good enough.
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Offline tautech

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Simon, you overlook a couple of things, automotive charging systems have been regulated to 13.8 - 14.2 since forever for FLA 12V batteries and the max voltage any charging system can deliver is also current regulated.

These 2 things control what a charge system can deliver and it's also governed by the SOC of the battery.

All that has changed in recent years is the battery chemistry and the max is more likely 14.4 - 14.5 V these days.
Still, any checks on auto charge systems need be done with a battery with a high SOC so that the charge system is NOT current limiting and then the charge cutoff can be accurately measured.
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Offline Simon

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If it's an actual battery management system like some modern cars have then fair enough, it takes care of itself like restarting the engine if you are sitting in traffic running you electric air conditioning and the battery gets low. But run-of-the-mill vehicles that just connect everything in parallel don't run that high. My last car ran 13.8V I had a constant display on it.
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Offline tautech

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If it's an actual battery management system like some modern cars have then fair enough, it takes care of itself like restarting the engine if you are sitting in traffic running you electric air conditioning and the battery gets low. But run-of-the-mill vehicles that just connect everything in parallel don't run that high. My last car ran 13.8V I had a constant display on it.
Understood, however I'd never trust a dashboard meter to be particularly accurate let alone the average vehicle owner having the knowledge to properly interpret it. Charge failures need prompt alert to the driver and I wouldn't care for anything other than a red charge light alert.

Still, that 13.8 V display is typically the lowest max you want to see a FLA charging system maintain.
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Offline Mechatrommer

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older battery having trouble reaching 13.8V let alone 14.4V. i monitored few battery and with 14.4V charger, some of them can constantly suck 0.25-0.5A and get hot. hot battery is not a good sign (hydrogen discharge) i boomed one of those 60AH'er right next to my ear while welding its rusty holder to a car with it sat right next, and being (over?) charged (13.8 - 14.4V) overnight. i got a warning of pissing smell, and read about hydrogen discharge a night before, and remember did a hydrogen pop experiment in school decades ago. a real stupid move i didnt take the hints, now i know and the puzzles now all connected together nicely and it will stick in my head pretty well i guess. sometime i believe a little bit of knock on our head or ringing bell echo from the ear can improve memory retention and attention, even on aging brain.
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Offline Simon

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If it's an actual battery management system like some modern cars have then fair enough, it takes care of itself like restarting the engine if you are sitting in traffic running you electric air conditioning and the battery gets low. But run-of-the-mill vehicles that just connect everything in parallel don't run that high. My last car ran 13.8V I had a constant display on it.
Understood, however I'd never trust a dashboard meter to be particularly accurate let alone the average vehicle owner having the knowledge to properly interpret it. Charge failures need prompt alert to the driver and I wouldn't care for anything other than a red charge light alert.

Still, that 13.8 V display is typically the lowest max you want to see a FLA charging system maintain.

It was a CAN bus display so it would have been either taking it from CAN bus data or i would hope that someone that can design a CAN bus device would be clever enough to measure voltages to 0.1V!
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Online T3sl4co1l

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Simon, about an hour later and battery voltage rose to the set 14.25V (as it turns out) and current started to decline.  After about three more hours, it was still taking 1.5A charge, where I decided to cut it.

Doing the full charge at 13.8V will certainly (for the wet lead acid formulation) result in an incomplete charge state, and getting there will take exponentially longer than doing it at a slightly higher voltage.

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Offline Simon

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well I expect cars err on the side of caution. You can't drive around indefinitely at 14.4V as you will knacker the battery. Given that the battery just works to start the car in most use cases 13.8V float is probably deemed to be a compromise. If i am manually charging i too will use in excess of 14V for speed with a current limit but unless the vehicle has a BMS they have to compromise. The alternator current limit is to protect the alternator not the battery. Modern Audi's have a load of BMS gear attached to the battery i am told and it looks after the battery to the point of restarting the engine if it's off and the ignition is on and the battery voltage is dropping.
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Offline tautech

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Well, so what? It's taking current at a lower voltage because it's in a discharged state.  As the concentration of Pb-->PbO2 and PbSO4-->Pb rises, the cell potential also rises.  (In fact it's up to 13.74V already.)  When all surfaces are fully charged, the voltage levels off somewhere around there (when under some degree of charge, because again, overpotential).  I'm going to float it at 14.2 for a while (preferably 12-24 hr, not sure if I'll get that much time on it tonight) to ensure a full charge (desulfation, to the extent that it can be performed at all).

Tim
You don't get a maintenance charge until 15V (gassing charge) where you'd get any benefit from desulphation and really you don't want to go there with the modern sealed FLA.

IMO the old noisy generators and their spikes where better at battery desulphation than the modern alternator.
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Offline Simon

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I thought the old "generators" or dynamos were supposed to be smooth DC. It's all you hear about from the old cranks that want to keep their dynamos that they are better because of the smooth output. In reality the 3 phase that get rectified are pretty good
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Offline soldar

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Old (dynamo) regulators were extremely simple. Two relays. One would close above a certain voltage and would disconnect the generator below that. This was to prevent the battery from discharging through the generator. A diode could do the same job today.

Another relay kicked in above a certain charging current and opened the NC contacts which put a resistor in series and this limited charging current.

That's it.

You could have all sorts of problems if contacts got stuck or voltage or current activation got out of whack.
« Last Edit: October 21, 2019, 03:48:57 pm by soldar »
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Offline Simon

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yea, but all the old farts still harp on about the good old days of dynamo's
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Online floobydust

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Any suggestions for equalize charge voltage on FLA? Trojan gives 2.7Vpc for 16.2V which seems pretty high.
I had 12.7V at rest and levelled off at 14.7V at 0.5A (2.45Vpc) overnight.

One particular car maker has ~135mA parasitic drain due to the ECU. The batteries would barely last 3 years. I think a firmware fix got it down to 70mA. An ECU typically does a fuel-pump run to cool the fuel rail (anti-percolation), a canister-purge after parked for hours, TPMS checks etc. - lots of stuff after key off which drains any surface charge.
 

Offline Simon

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Well my car tonight according to a cheapo USB charger went as high as 14.5V dropping to 14.3-14.4. However I did leave the dash cam on all weekend and do short journey's so assuming the alternator can be controlled maybe it knows that the battery is low (started at 12.3V). I'll see how it performs over the next week
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What car maker does have 100mA drain?  Such ECU would not pass even the basic LV124 tests.  ;D
 

Online Yansi

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Well my car tonight according to a cheapo USB charger went as high as 14.5V dropping to 14.3-14.4. However I did leave the dash cam on all weekend and do short journey's so assuming the alternator can be controlled maybe it knows that the battery is low (started at 12.3V). I'll see how it performs over the next week

So the car charges at over 14 volts after all?  :-DD 
 

Offline Simon

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Like i said the battery was low. And like I said this is not universal, my last car was 13.8V and commercial vehicles 27-27.5. Lets see how it goes over the week as the battery charges back up again from the weekend abuse.
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Offline tautech

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I thought the old "generators" or dynamos were supposed to be smooth DC.

Well as smooth as you can get with a carbon brush commutator and an electromechanical regulator.  ::)
Old vehicles often didn't have radios so when you fitted one all sorts of suppression was required so to not have to a crackling whistling mess varying with RPM.
Sure some of it was the ignition points but all of it, certainly not !
If you've every had the lid off one of the old points regulators to make a charging cutoff voltage adjustment the chattering points make it plainly clear where all the interference was coming from.

Quote
In reality the 3 phase that get rectified are pretty good
Especially when solid state regulation came in. Still, early alternators had electromagnetic regulation with all their EMI but to the greatest degree they were reliable until silicon technology advanced sufficiently to give reliable replacements.
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Offline Simon

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Yes i studied dynamo regulators closely when I cansidered designing a replacement.
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Online floobydust

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What car maker does have 100mA drain?  Such ECU would not pass even the basic LV124 tests.  ;D

Subaru are notorious for high parasite drain and mysterious dead batteries, across many models.

2015-2017 Subaru Legacy, Outback
TSB Number: 11-176-17, NHTSA ID: 10125883, TSB Date: Dec.15, 2017
Failing Component: Electrical System: Battery
Summary: This bulletin announces availability of reprogramming files to optimize the ECM for control of
battery charging functions.  Depending on vehicle use conditions, the battery state of charge value
may differ slightly from the actual value.  The new logic will enhance charging system control and
result in improved battery life.

TSB Number: 11-174-17R, NHTSA ID: 10131689, TSB Date: Aug.8, 2017
Failing Component: Electrical System: Battery
Summary: This bulletin announces the availability of reprogramming files to optimize the ecm and address the following customer concerns: * check engine light coming on (with DTC p05a0 stored in memory). * potential battery discharge (dead battery)
 

Offline Marck

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This isn’t really relevant to the original question but might be useful  And its nice to be able to contribute with something i actually know about and have some experience.

Some modern commercial vehicles will reduce charge voltages at idle to reduce emissions. This was a common issue 10 years ago when i was designing radio installations for emergency response vehicles. The best work around for this was to have the manufacture of the vehicle disable the feature either in the ECU or having the alternator modified to supply a normal charge voltage at idle.  More modern systems now will measure accessory current use to maintain acceptable charge profiles quite often we see problems where installers will connect accessories before the measurement point causing problems with charging. Simply moving the connection point can resolve some problems

Another problem this caused was very low voltages at start up which would cause problems with all sorts of equipment causing them to freeze up or worse.   The best work around in 24 volt systems was to use a dc-dc converter and run the radios / accessories at 12v.  This added another point of failure but was often the best bandaid fix where they wanted to keep the serviceability of the vehicles standard so no complexity was added to normal vehicle systems.

For 12v systems in cars and such the other option was to introduce a delayed power up of the accessories for about 30 seconds to allow voltages to stabilise post engine start.  Some of these vehicles would drop well below 10V during start up the issue here was that the voltage would cycle 8V - 11V - 8v during the couple of second start sequence and cause issues with the power up of the equipment.

Some vehicles will wake up ancillary systems when they detect the keys proximity to the vehicle so people that park their cars close to where they are moving around with keys in bags and pockets can see problems if the vehicles are not regularly driven and the batteries are getting older.  I have read about this being an issue  with some BMW models. 

I can tell you from experience with large vehicle fleets that charging systems in vehicles are not all that interested in the best charging profile for the batteries and the use of either solar or regular charging of batteries with a mains charger to make sure that the batteries regularly reach 100% SOC will increase the life of the batteries sometimes by 25%.

Another point of reference i have with battery charging in telecommunications dc systems i have is with sites that had unreliable power the batteries would last longer. Getting discharge / charge cycles as opposed to batteries that never or rarely got cycled.  Typically the batteries that where discharged to some extent would last 7 years vs 5 years for batteries that where on a float voltage consistently.  This obviously is on a curve batteries that where cycled regularly and to deep discharge had a shorter life.  We had a policy of not using automated discharge cycles to mitigate the risk of having reduced capacity if a power outage was to happen during that cycle. 


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Offline tautech

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I can tell you from experience with large vehicle fleets that charging systems in vehicles are not all that interested in the best charging profile for the batteries and the use of either solar or regular charging of batteries with a mains charger to make sure that the batteries regularly reach 100% SOC will increase the life of the batteries sometimes by 25%.
This ^  :-+
Also acquired from 45+ yrs of owning and operating several classes of vehicles.
I try to do an annual freshening charge right to the max charge V of that class of battery to where you can see the drawn current drop right away to a couple hundred mA or less.
Any cheap SMPS bench PSU with voltage and current metering is perfectly suitable for this.

Quote
Another point of reference i have with battery charging in telecommunications dc systems i have is with sites that had unreliable power the batteries would last longer. Getting discharge / charge cycles as opposed to batteries that never or rarely got cycled.  Typically the batteries that where discharged to some extent would last 7 years vs 5 years for batteries that where on a float voltage consistently.  This obviously is on a curve batteries that where cycled regularly and to deep discharge had a shorter life.  We had a policy of not using automated discharge cycles to mitigate the risk of having reduced capacity if a power outage was to happen during that cycle.

Interesting and it makes perfect sense.

Having done a recent solar powered installation for community data provision when setting up the charge controller for a series/parallel bank of four 165 Ahr SLA's there were several options for battery maintenance based on the battery type used.
https://2n1s7w3qw84d2ysnx3ia2bct-wpengine.netdna-ssl.com/wp-content/uploads/2014/02/150V-TS-MPPT-Operators-Manual.pdf
P12
It is important to select the battery type that matches the system battery to ensure proper charging and long battery life. Refer to the specifications provided by the battery manufacturer and
choose a setting that best fits the recommended charging profile.


DIP
Switches
4 - 5 - 6
                       Battery        Absorp.                   Float                  Equalize              Equalize
                        Type         Stage (Volts)          Stage (Volts)       Stage (Volts)         Interval (Days)
     
off-off-off 1 -     Gel               14.00                     13.70
off-off-on 2 - Sealed*            14.15                      13.70                14.40                        28
off-on-off 3 - Sealed*            14.30                      13.70                14.60                        28
off-on-on 4 - AGM/Flooded     14.40                      13.70                15.10                        28
on-off-off 5 - Flooded             14.60                      13.50                15.30                        28
on-off-on 6 - Flooded             14.70                      13.50                15.40                        28
on-on-off 7 - L-16                  15.40                      13.40                16.00                        14
on-on-on 8 - Custom            Custom                    Custom             Custom                   Custom
* “Sealed” battery type includes gel and AGM batteries
Battery Type - The most common battery type associated with the specified charging settings.
Absorption Stage - This stage limits input current so that the Absorption voltage is maintained.
As the battery becomes more charged, the charging current continues to taper down until the battery is fully charged.
Float Stage - When the battery is fully charged, the charging voltage will be reduced to the Float voltage setting.
Equalize Stage - During an equalization cycle, the charging voltage will be held constant at the specified voltage setting.
Equalize Interval - The number of days between equalization charges when the controller is configured for automatic equalizations (settings switch 7).


Then in addition there's Equalisation management as follows:
Switch 7: Battery Equalization
Choose between manual and automatic battery equalization charging. In the manual equalization setting, an equalization will only occur when manually started with the push-button or when
requested from the equalize menu on the TriStar meter. Automatic equalization will occur according to the battery program specified by settings switches 4, 5, & 6 in the previous step. In both settings (auto and manual), the push-button can be used to start and stop battery equalization. If the selected battery charging setting does not have an equalization stage an equalization will never occur, even if requested manually.


You'd hope it all works as expected as the price of the battery bank was $$$  :scared:
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Offline Marck

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Most of our DC systems are Eaton but we recently in the last few years used some Tristar gear for some solar installations.  We found them quite good but with a slightly higher failure rate than the mains powered Eaton equipment but the cause of those failures could be put down to the duty cycle being much higher with daily discharge cycles.  Don’t get me wrong we are only talking about 2 issues across 5 sites in 4 years.  We just started trialing  Victron inverter / chargers Thats because we also need inverters to run an air conditioner and one other piece of mains powered equipment along with the nice http based UI that we can access remotely to keep an eye on things and ease of gathering trends. This means that we only need to keep one spare device that replaces 3 seperate units a mains charger/inverter/solar charger. Set up in pretty much a plug and play setup.  By no means am i suggesting that the Tristar gear is not as good as the Victron stuff its just ease of serviceability for us. Time is the only real judge of performance for most of these things.

Most quality battery manufacturers will specify an ideal charge profile based on the battery and typical operating temps in sites that are not temperature controlled they quite often recommend  a change in charge voltages for temps outside a specific range.  Most of the better chargers will have a temp probe that can trigger a change in charge profile for excursions outside the optimum. 

Good luck with your service power is always a expensive and difficult thing to get spot on for long trouble free service.

Just another bit of advice on the batteries that claim much more than 150 AH capacity in the standard long tall form factor used in these installations.  Quite often these claimed capacity’s are at a lower discharge rate compared to the competition.  A reasonable rule of thumb is if the battery dose not weigh more the capacity may not be as claimed. On average a good quality 150AH battery will weigh around 47 kilograms each if the claimed capacity dose not come with extra lead in the battery unless they have some design advantage its time to dig into the spec sheet and see whats going on.

Its almost at the stage where Lithium is the correct choice for new installations.  The increase in available discharge capacity the increased cycle count and the huge weight savings the lifecycle cost is almost at breakeven point.  The only thing that is holding back the revolution is the cost of failures smudges the cost benefit line a bit.  A out of warranty replacement of a battery is double that of lead acid.  And at this point there is not quite enough long term data on any particular manufacturers lithium service life to adopt that risk.   For any existing installations that wont allow constant voltage charging and will require upgrades of chargers and such its a little further away.  But my personal opinion is that within 5-10 years we will not see many  lead acid battery installations being used in telecommunications.


Now we are way off topic.
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Offline Tomorokoshi

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what vehicles use AGM batteries?

What cars use AGM batteries? Mine do!

Just charged up some spare batteries using my HP 6114A power supply. Set to the recommended charging voltage of 14.4V and set the current limit to 1A. Then I slowly adjusted the voltage down to keep the trickle current to around 100mA.

This all started because one of the batteries stopped taking a charge after being used for around a month. That was maybe 3 years ago. Took it to the store where they used the battery tester, declared it failed, and so I was able to submit a warranty claim for a free replacement.

I never got around to getting rid of the failed battery, and before I got the coupon for the replacement I bought another one of a different brand and construction. Through a series of mishaps I now have all three batteries not installed in a car.

Anyway, as part of topping off the two known-good batteries I connected the failed battery to the HP 6114A. No current. Well, that being the case, I instead used the HP 6186C 300V / 100mA Current Source to charge it. At 10mA it drove to something like 100V.

Over the course of a few hours the voltage dropped to maybe 15V, so I charged with the HP 6114A instead. For the most part it topped off at the same voltage as the other two, and after 4 weeks the two good ones are 12.8V, and the "bad" one is 12.7V.

I don't know what the failure process was and I don't know what may have fixed it. I have not signficantly load tested it yet.
 

Offline tautech

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@ Marck
The installation we did was purposely kept all DC and powers just a DC POE switch that in turn powers all the Ubiquity data transmission HW. NO freaking inverters !
Here's a link to some pics of the installation with a link to the docs of the DC POE switch we used:
https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/msg2698096/#msg2698096

The 4 batteries are German SLA's and mighty heavy buggers @ some 55kg ea !  :scared:
Yep and we used the Tristar solar controller battery temp sensor.  ;)

Anyways, IMHO it's over designed to hell as any one bit of HW draws under 30W max ea and there's 900W capability from the panels for a measly ~100W max load.
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Offline Marck

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That Ubiquiti gear is good value for money. We recently used a couple of the Air fibre 24hd links for temporary coms over about 2Km.  A solid gigabit link and lets say very rough one eye closed  alignment.

That looks like a neat little switch.  Here that would probably cost hundreds of $$.  The US gets all the good cheep toys. 

M
 


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