Lead acid "smart" charger being weird or actually smart?

[paulca]

I bought a trickle charger for the car battery.  I was hoping to get one which would float the battery permenantly.

Instead the 0.5A charger when put onto a brand new battery, charged it to 14.50V and then disconnected itself.  I left it for days and the voltage came down to 12.85V and it didn't enable charge again.

However...  I then connected it to an old battery and it is behaving completely differently.  It's like it "knows" there is a dead cell or a low cell and it's pushing it up higher and higher towards 15V.  The battery status indicator says, "Charge"...  it's charging it.

The battery is knackered, but is the charger smarter than I give it credit for?  It didn't bother "equalisation charging" the "good battery", it just boosted and quit.

[Stray Electron]

    A 14.50 Volt charge?  That sounds way too high for a LA battery!  I always charge my flooded LA batteries at 2.2 to 2.25 volts per cell. But as they age they often won't even fully charge up to that voltage. 

    It would probably help if you posted a link to the charger that you're using.  But FWIW the 'smart charger" that I'm using does seem to detect a bad battery in just a few minutes and and it displays "bad battery" and stops charging. OTOH on a good battery it does continue to "float" charge the battery.  I checked one of the chargers (I have two) two days ago and it's still maintaining a float charge on a battery that I connected it to about three months ago. 

   This is the charger that I'm using https://www.amazon.com/Schumacher-SP1297-Automatic-Battery-Maintainer/dp/B0756PV96N/ref=sr_1_11?dib=eyJ2IjoiMSJ9.Dy_dSJGpOue_tzMr5nCNSxtI0gOSR5_Q-m9TWBwRCyuVPjW3Rs-ZqsIkHHsu6e8pJi_y4p6QOPeDnNxQQNJW217HxHqzXq7CmLH0Wme1PSl9IDcIBnXsdd9mfSLvSb505lIdBa3K9dmvUg4i8n3xr6p_RqIGKuL0SSrzA7L1o1YCsGV7mcklvQXo0bbcpHsYIUgN2yTibr8Nzp70p_Dh9RjhN2deGMEXG_7TfxddfmuAYgbS2gteIeGIQrXHNObYD_d8xfftXvlwphEyXcRdFZbmAHx7F9aAcvBG1xnVtRQ.R1m78lRbWpWpGLD5EX320Ypv-so_AnjU7DmK4Ylqjkk&dib_tag=se&keywords=schumacher%2Bbattery%2Bcharger&qid=1769097569&sr=8-11&ufe=app_do%3Aamzn1.fos.9fe8cbfa-bf43-43d1-a707-3f4e65a4b666&th=1


  Edit to add a bit more info:  When I connect my charger it asks if the battery is LA or Li-Ion. If I don't press the button then it assumes that it's LA and after about 30 seconds it starts charging and shows the percentage of the battery charge.  If the battery is good, it continues doing that until the battery reaches 100% charge and then it switches over to float and shows "floating" and that continues indefinitely..  If I press the button then it will shows "100% charge" and then "good".   But if the battery is bad then it will detect that is about a minute and displays "bad" and it appears to stop attempting to charge the battery.

[mtwieg]

A battery charger having "smart" in its description is completely meaningless IMO. In some contexts it might matter (for example, I think it has some well-defined meaning for EV chargers), but not for 12V PbA chargers.

14.5V isn't unreasonable for absorption mode, especially if the battery is cycled (i.e. not standby). If it's closer to 15V, then it's possibly trying to do an equalization cycle, but that should not last very long (less than an hour IIRC).

[SteveThackery]

    A 14.50 Volt charge?  That sounds way too high for a LA battery!

My car sometimes pushes 14.5V at its battery just after starting. I don't know how widespread it is, but some - maybe most - modern car alternators are controlled by the ECU, to provide "smart" charging. Years ago alternators were autonomous and looked after the charging voltage internally.

[Stray Electron]

A battery charger having "smart" in its description is completely meaningless IMO. In some contexts it might matter (for example, I think it has some well-defined meaning for EV chargers), but not for 12V PbA chargers.

  I completely agree!  A lot of devices are referred to as "smart" but all it really means is that they're controlled by software and often times, there's nothing smart about how they operate.  And with regard to how they control a battery charger every brand is probably different.  That's why I suggested that the OP list the brand and model charger that he's using. Maybe someone has experience with that model charger.

    FWIW I checked one of my batteries today that has been connected to a charger that I described earlier.  I haven't driven that vehicle in a few weeks and I neglected to put it on a charger until a few days ago and the battery was pretty well run down but today the battery measured 12.65 volts after I disconnected the charger and the charger said that it was fully charged. But when I reconnected the charger it said that it had a 92% charge.

   Just for comparison I had some work done on a different vehicle yesterday and they checked the battery and told me that it was weak and needed to be replaced.  I measure that battery today and it measured 12.47 volts.

[J-R]

I've had good results with this: https://no.co/genius1

[paulca]

So this is the charger:
https://www.maypoleltd.com/product/mp7402-0-5a-12v-dc-automatic-trickle-battery-charger/

I didn't buy it to be smart, but I notice it says that.  Next time I'm going to buy a 13.6V power supply instead.

I put it out of it's missery.  It's trying to equalisation charge a 70Ah Yassa starter battery that has been in service for 2 years and flattened 3 times.  After 24hours at 14.70V it has hit the point where 0.5A will make it charge no more.

[MrAl]

I bought a trickle charger for the car battery.  I was hoping to get one which would float the battery permenantly.

Instead the 0.5A charger when put onto a brand new battery, charged it to 14.50V and then disconnected itself.  I left it for days and the voltage came down to 12.85V and it didn't enable charge again.

However...  I then connected it to an old battery and it is behaving completely differently.  It's like it "knows" there is a dead cell or a low cell and it's pushing it up higher and higher towards 15V.  The battery status indicator says, "Charge"...  it's charging it.

The battery is knackered, but is the charger smarter than I give it credit for?  It didn't bother "equalisation charging" the "good battery", it just boosted and quit.

Hi,

You need to monitor both voltage and current to get an idea what is happening.  Some chargers have four stages.  You also need to monitor temperature.

14.5v is not unusual at all.  It's actually good.  If the internal resistance went up a little then you need more voltage in order to force enough current through it to charge it enough.  The voltage would usually gradually decrease to maybe 13.8v but might go lower depending on the charger.
The voltage can change significantly with temperature also so keep an eye on the battery temperature.

You can look up the four stage charger dynamics on the web to get some idea how they work.  They would be considered 'smart'.

For the simpler type, the charge current stays at some limit for a time and as the voltage rises the current becomes lower and lower.  The battery would be considered fully charged when the current drops to some lower cutoff level.

[paulca]

The battery was a 70Ah Yuassa starter battery.  It got left stood up for 3 weeks due to snow and ice on the driveway.  The car is notorious for waking up at the slightly hint of a key and draining it's battery.  So needless to say it went "chug, click, click" next time.  I kept it alive with a bench power supply so I could use the car until I bought a new battery.

I only bought the charger because I was hoping to avoid a next time and only need to slip this little charged under the bonnet in such occasions.

The old battery now goes onto the 50W unused solar panel and charge controller in the garage where it will be absorbed and floated every day with no load as the backup jump starter battery.  Should I break my actual battery again (it's likely) I can lift this one, use it to jump the car and then put it in the car and take it with me.

[golden_labels]

“Smart” is the old “AI” — a marketing term devoid of any real meaning. “Smart charger” might be anything from microcontroller charger with user-selectable options to a single comparator turning off charging and lighting up a LED.

But this is not the case here!

• Product description never uses term “smart”, only “automatic”.⁽¹⁾
• The description is very clear about implementing some kind of an algorithm to detect what state the battery is in.

So, contrary to some suggestions here and what would word “smart” alone indicate, there seems to be employing some decision process.

The page mentions charger is rated only for batteries up to 100 Ah. You say you use it on a pretty beaten up 70 Ah battery. Perhaps, being not far from its limits, from charger’s perspective it’s trying to fill a bottomless void?

⁽¹⁾ It’s in “smart chargers” category, but this is an established class of chargers. Encompassing all I mentioned in the first paragraph, contrasted with old-style uncontrolled chargers.

[paulca]

I scan read the instructions.  They don't mention an equalisation phase. 

But, no it wasn't able to get the battery up that high in voltage.

The battery itself has one of those fairly unreliable sight glasses.  It's meant to be Green for charged, black for needs charged and red for broken.  All it shows right now is black, even while it cooked at 14.7V.  I suspect at least one dead cell in there.

Those sight glasses...  my old solar battery, a marine starter battery shows green.  It couldn't start a kids toy it's been abused that much.  It used to be my starter backup, now it has expired from that purpose... still shows a green indicator though.  I expect this just means it doesn't have a dead cell, it just has all dead cells.

[radiolistener]

For lead-acid batteries, a typical cyclic (bulk/absorption) charge voltage is around 14.4 V, not 14.5 V, although the exact value depends on the specific battery type (flooded, AGM, gel) and temperature (!).

This voltage level is intended for cycle use, i.e. fully recharging a battery after a significant discharge.
It is not suitable for permanent connection.

For standby / float charging, the correct voltage is significantly lower — typically 13.6–13.8 V for lead-acid batteries. Maintaining a battery at 14.4–14.5 V continuously will cause accelerated aging due to excessive gassing, corrosion of the positive plates, and electrolyte loss. Such high voltage applied for a long time may lead to rapid battery damage even with low current.

It is also worth noting that even at a proper float voltage, a battery connected to a charger permanently will still age over time. The degradation process does not stop completely, it is merely slowed down enough to avoid rapid damage.

[radiolistener]

After 24hours at 14.70V it has hit the point where 0.5A will make it charge no more.

Charging a lead-acid battery above 14.4 V causes excessive gassing, which leads to internal damage such as electrolyte loss, positive plate corrosion, and accelerated aging. For this reason, raising the voltage to 14.7 V may lead to battery damage.

Some modern battery types (for example Ca/Ca lead-acid batteries) may specify a higher absorption voltage, but this must be confirmed in the manufacturer’s datasheet, and even then it applies only to cyclic (bulk/absorption) charging, not to continuous operation.

In float service, even 14.4 V is excessive and will damage the battery if the voltage is not reduced or disconnected after the battery reaches full charge.

A common end-of-charge criterion is when the charging current falls to approximately C/100 (1% of nominal capacity), or when the charge current stops decreasing and remains essentially constant for several hours at the absorption voltage.

[Heisen]

They don't mention an equalisation phase. 

I think equalization phase is done on flooded lead acid batteries not SLA (sealed lead acid) batteries, the ones where you can't top up the liquid.

I left it for days and the voltage came down to 12.85V and it didn't enable charge again.

That is odd, it should stay at 13.5V or 13.6V, unless there is some load connected or the battery is old, degraded or has high internal resistance or that charger is not entering float mode.

[paulca]

My car always puts 14.50V across the battery.  Most of the batteries with datasheets or it actually printed on them, says 14.50V.  These are specifically LA starter batteries.

Weirdly.  Yuasa ... I can't find any charge voltages on their datasheets or their website in general.  The best they can do is say, "Use a compatible charger".

The solar panel controller for the LA is however set to 14.40V for a 1 hour absorb and 13.6V float.

[paulca]

I left it for days and the voltage came down to 12.85V and it didn't enable charge again.

That is odd, it should stay at 13.5V or 13.6V, unless there is some load connected or the battery is old, degraded or has high internal resistance or that charger is not entering float mode.

I found in the manual it will watch the battery drop down to 12.8V when it will reset back to the 14.50V bulk charge again.

[shapirus]

My car always puts 14.50V across the battery.  Most of the batteries with datasheets or it actually printed on them, says 14.50V.  These are specifically LA starter batteries.

My car floats the battery at 14.35 V, at least at the temperature when I last measured it, and that was -10 C / 14 F, which is rather cold. It'll be interesting to compare it with summer time. I measured it many times in the past, of course, but forgot what it was.

At the same time, I have some batteries with liquid electrolyte lying around, and when I try to float them at about 14.2 V at room temperature, I can clearly hear the sound of electrolyte breaking down inside (known as "boiling"). So definitely not a good voltage to float the battery at. Perhaps whatever is used in UPS systems would be more reasonable, and that is typically about 13.6 V.

[paulca]

My car has a voltmeter on the dash and it always sits just above 14V.  In the cenrtal console I have a auxilary socket with a USB quick charger in it and it has a voltmeter (not exactly accurately reliable) which always read 14.50V while the engine is running.

Except the last time the old battery was in the car, last friday evening.  The soldenoid did not even click.  The dash computer reset though.  The USB charger volt meter said 8.3V and rising.  When I pressed the start button again the car just ignored me. I switched it off, waited for a few minutes, switched it back on and got, 11.6V.  Turned the ignition on without cranking and it began to fall.  "The battery has left the building."

[SteveThackery]

The solar panel controller for the LA is however set to 14.40V for a 1 hour absorb and 13.6V float.

I've worked on electrical clock systems in the past. Those with battery back-up would often use 12V LA batteries, or multiples thereof.

The batteries were not "managed" - that is, they didn’t get any absorption charging or equalisation charging. Rather, they were invariably floated at 13.8V. That is 0.2V above what @paulca reports, presumably because of the lack of management. Batteries were typically changed every five years.

[tautech]

So this is the charger:
https://www.maypoleltd.com/product/mp7402-0-5a-12v-dc-automatic-trickle-battery-charger/

I didn't buy it to be smart, but I notice it says that.  Next time I'm going to buy a 13.6V power supply instead.

I put it out of it's missery.  It's trying to equalisation charge a 70Ah Yassa starter battery that has been in service for 2 years and flattened 3 times.  After 24hours at 14.70V it has hit the point where 0.5A will make it charge no more.

Which won't do any conventional LA battery any good at all.

In the many decades I have twisted spanners on engines, those with the old generators and electromechanical regulators were specified a charging range of 13.8-14.2V.
Today with alternators and using modern battery chemistries use 14.4-14.5V for max charging voltages.

Conventional flooded LA batteries like regular work to keep sulfation to a minimum something the old technology regulators helped with by their constant make-break of contact causing much electrical noise helping to break down the tougher sulfation bonds.
Gassing charges do this too but the loss of electrolyte in the modern sealed non-serviceable batteries can become a problem.

[floobydust]

0.5A charger is not enough for a car battery unless in perfect health. Basically a flea fart. Best sized for motorcycle batteries. You need at least 1%C.

Embrace the future. Management replaced by smart kode lol.

[MrAl]

The battery was a 70Ah Yuassa starter battery.  It got left stood up for 3 weeks due to snow and ice on the driveway.  The car is notorious for waking up at the slightly hint of a key and draining it's battery.  So needless to say it went "chug, click, click" next time.  I kept it alive with a bench power supply so I could use the car until I bought a new battery.

I only bought the charger because I was hoping to avoid a next time and only need to slip this little charged under the bonnet in such occasions.

The old battery now goes onto the 50W unused solar panel and charge controller in the garage where it will be absorbed and floated every day with no load as the backup jump starter battery.  Should I break my actual battery again (it's likely) I can lift this one, use it to jump the car and then put it in the car and take it with me.

Hi,

You mentioned a solar panel.  I used on to keep my car battery alive for a couple years.  I did not drive that car that much so the battery would run down over time, and I did not feel like going out there just to start the car and let it run for a few minutes to keep the battery charged, and it was parked a little too far from the garage so I could not really run an electrical cord out to the car for a plug-in charger.  I set up the solar panel on the roof and tied it down with some hefty straps, and wired it up to the battery through a diode.  It kept it charged, but I was worried about overcharging so I eventually hooked up a charge controller with the diode.  It kept the battery fully charged with no problems.  I think it was a 100 watt panel, and I needed a bracket to be able to mount it on the roof.
It worked surprisingly well.
At first I tried to keep the panel inside the car, but the windows blocked out too much of the sunlight so it would not charge enough.
At some point I designed a voltmeter for inside the car that would transmit to a receiver in the house so I could monitor the charging 24 hours a day 7 days a week by recording the readings on the computer that converted the received signals into voltage readings.
It worked out nicely and I could see how the charging worked when there was bright sun and when there was cloud coverage.  Very informative.

[paulca]

I have considered a proper "ambilical".  I even had a thread on here about it and got good advice.

There are many options for power about 5 meters away in the garage, two solar systems, a 24V.1kW rig with inverter and a 12V "Lead acid minder" 50W setup.

The "ideal" would be to just connect that 50W panel with it's charge controller to the car via an ambilical.

The practical aspects of this however just didn't give me enough of a "Yes!" feeling to bother.  I would cable that can carry at least 1A of current without more than 0.5V drop.  It can get "slung" over the garage ceiling beams, but when it gets outside it has to be clipped into the wall above the door, back down and have somewhere to hang it up when not in use.

I suppose as an interim, I do have a 25m reel of 20AWG twin core.  I can just drag it out of the garage when needed.  Put some croc clips on the end of it.

I have to be some what "nasty" to the car and battery in coming months as a new job requires me to be in the office one or two days a week.  That means the car gets abused with a 1 mile drive to the train station and another back in the evening, both cold starts in winter, not enough time to warm the car up (blue dash light still lit), not enough time to replace the cranking load in charge time either.

The new battery will be fine this winter while I sort something out.  At £120 or so a pop 1 battery a year isn't 'that' bad, could be better.  I could buy cheaper batteries, but having tried that already, they don't survive the first flattening, the premium brand batteries recover after mistakes better and will keep you going until you can source a new one.  (Mine requires swapped posts which means you have to order it usually).

[tautech]

I wouldn't sweat the short run if your car is an easy starter.
Modern alternators pile a heap of current into a battery.

A top-up charge every few weeks should keep it in good order.

[shapirus]

That means the car gets abused with a 1 mile drive to the train station and another back in the evening, both cold starts in winter, not enough time to warm the car up (blue dash light still lit), not enough time to replace the cranking load in charge time either.

That should be more than enough time to replenish the energy spent on cranking.

Let's make a very rough estimation based, for example, on my own recent measurements in cold weather (starting a 4-cyl 2L diesel engine):

- peak discharge current, 5 ms measurement window: 613 A
- peak battery charge current after the engine has started: ~60 A
- charge current after ~30 seconds (when still idling): settles at about 20 A

So let's say it takes 300 A on average during 5 seconds at 12 volts (much less in reality, I think, but let's make it an upper estimate) to get the engine started. Energy spent: 300 A * 12 V * 5 s = 18000 J.

Now, to replenish this during charging at 20 A (assuming the same 12 V) we need this much time: 18000 J / (20 A * 12 V) = 75 s. That's a pretty short time. Of course there are losses and all, but you get the idea about the order of magnitude of these things.