charging a fully discharged car lead acid battery

After a couple of days (daytime only) at 1 amp charge, it is now reading

12 volts no load. Interesting that no matter where I dial in the current, it stays at 12.0 volts. The battery is acting like a voltage regulator of sorts.

It's just under two years old, original factory battery. When I topped it off with distilled water, tops of the plates looked great. Looked just like new finned aluminum heatsinks, clean and no gunk. There was some oil slicks on the electrolyte, no doubt from the red bearing grease someone (the factory?) had smeared all over the terminals. There was semi liquid red grease underneath the caps too.

Isn't there a better choice for corrosion protection than regular petro grease? In the 80's, I remember a cream colored paste for that purpose.

Well, yes. Think I've said that. Many times. ;-)

But this won't *damage* the car alternator. It simply won't charge the battery.

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*A cubicle is just a padded cell without a door.

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

Think you said the maximum voltage of the bench supply was 12 volts. You can set the 'current' to whatever you like, but without the required voltage the battery won't get fully charged. You need near 14 volts to do this.

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*Remember not to forget that which you do not need to know.*

    Dave Plowman        dave@davenoise.co.uk           London SW
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Some auto repair experts and manufactures state that trying to charge a fully discharged car battery with an alternator can damage it. (note: it does not say WILL damage it but CAN damage it)

Boschusa.com: Q. Can I use my alternator to recharge a discharged battery? A. No! When installing an alternator, the battery should be fully recharged before vehicle use. In many cases, depending upon how thoroughly discharged the battery is, it can take 4-8 hours. Most technicians and DIYers don't want to wait that long so they just get the vehicle running, and figure that by driving the car around the alternator will charge the battery. In some cases with weather extremes the battery never gets fully charged, and in all cases the alternator is being overly stressed asking it to do a job it was not designed to do. This leads to premature failure.

popularmechanics.com: Use a battery charger until the open-circuit voltage is 12.6 volts. Avoid quick-charging, as the high current can warp the plates. If the battery is deeply discharged, don't use the engine's alternator to charge it by jump-starting and running the vehicle--the alternator is not designed to produce that amount of current for that long and may be damaged.

Given the high cost to replace an alternator and the not so do-it yourself friendly of replacing one on a front wheel drive car, it would be better when possible to go on the side of caution. The problem arises in not knowing which vehicle charging systems can or cannot handle running at the higher current, or which ones limit the current to levels that will not possibly cause damage.

I was wrong about the supply. It is 12 volts nominal, but it adjusts up to 14.0 volts. It is not a variable current supply, it is a variable voltage supply.

Without having followed the whole thread - I am somewhat confused!

You drove a car 50 miles with a flat battery? Either the battery has a low internal resistance (as it should have), and the depleted battery would keep the actual system voltage low. The car would not run (car management / ignition does not operate)

-or the internal resistance is very high (battery totally ruined), in which case the alternator is not "buffered" and voltage spikes way above 30V may occur. This usually blows all sensitive electronics.

(thus the advise never to unhook a battery in a running car)

Possibly the battery was not flat at all, just not powerfull enough for a start? (radio would work, as would lights?)

I take it the car in this case is an diesel powered oldtimer? :-) A damned robust car anyway!

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 - René

I must avoid long journeys with headlights ablaze, wipers going, heated rear window on heated seats, high powered stereo blaring, etc etc etc. Perhaps that's why my alternator is water cooled?

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*Dancing is a perpendicular expression of a horizontal desire *

    Dave Plowman        dave@davenoise.co.uk           London SW
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With a heavily discharged battery, the regulator in the alternator acts to keep the voltage at a maximum of about 14 volts. And although the internal resistance of a battery does change with state, it's always extremely low unless knackered. Otherwise it would not be capable of delivering the several hundred amps needed to start an engine.

Only engine electronics on that car was the ignition unit. It had a radio, etc.

Totally flat when I got to the car. Not even a glimmer from interior lights or engine warning ones etc at switch on. Even the clock had stopped.

No - carburettor V-8

A '74 Rover 3500S. Great fun.

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*I wonder how much deeper the ocean would be without sponges.

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

Charge it using a charger, rate isn't that important unless you do have alot of sulfation. Then you need to use a really high amp charger, 40amp or higher, to burn off that sulfation. You could have it tested at a decent battery shop for sulfation levels.(and any possible shorted or dead cells as well.) They'd have a charger designed for reviving problematic batteries as well. Jumping it off from flat dead is a no-no, especially with later model cars with loads of electronics and mainly an electronic altenator.( You can really do a number on the electronic regulator internalized in most late model altenators. Burnt diodes, fried control chip etc... trying to jump start and run with the battery that low.) Better to remove the battery and get it charged up before running the electronics off it. One big reason to go with "old school" auto's if possible, less to go wrong and rock solid reliability.( a heavy duty marine grade altenator with a competitive ignition coil and double duty external voltage regulator. If it's a stick you can just give it a push and you're off and running.)

I get the impression that this is "common knowledge" but I think I can persuade you that it's counterproductive.

The battery works by taking sulfate ions in and out of solution: sulfuric acid goes to lead sulfate, etc. Lead sulfate which is shed off the plates will fall to the bottom of the case and stay there as an insoluble precipitate. In this process, it removes sulfate ions from the process. It also removes lead from the plates.

The buildup of this precipitate may eventually short out the cell, plus the permanent loss of sulfate ions weakens the sulfuric acid and weakens the battery. The loss of lead may eventually lead to degradation of the plate.

If you take your time and reverse the sulfation process slowly, you won't have any of these problems.

How'd I do? Are you convinced?

In my opinion, there is really only one real stumbling block with reversing sulfation and that is time. If you have time, it can be fixed. If you don't, you'll just have to replace the battery.

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----------------------------------------------- Jim Adney snipped-for-privacy@vwtype3.org Madison, WI 53711 USA

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Right, it's six. Charging systems run at 14.1-14.4V. I'm guessing that the old 13.8V "standard" was actually what you could depend on at the load end. I gather that modern batteries use a slightly different chemistry (something about a bit of calcium added to the lead in the plates) which makes them able to tolerate slightly higher voltages without hydrolysis. I'm not really clear on this.

I agree completely. If you have time this is not at all difficult.

Keep in mind that for most applications, you don't have to completely reverse the sulphation, all you have to do is get the battery back to a state where it can be put back in service. Once back in service, normal usage will continue the restoration process.

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----------------------------------------------- Jim Adney snipped-for-privacy@vwtype3.org Madison, WI 53711 USA

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Yes, it's just like a big capacitor which you're slowly charging up.

There is one thing that you should check occasionally, and that is to verify that you don't have a shorted cell in there, which would make this a 10V (or 8V) battery. To test for this, just leave it off the charger overnight and check the open circuit voltage in the morning. It should be above 12V.

I know you did this earlier, and at that time it was still only up to

11 volts. At that time it looked like this was reasonable, but by now, I think you should be back up to "normal." Haven't you put ~50 Amp-hrs into this thing so far?

If the voltage drops to ~10V, then you have a shorted cell, and I really don't think that is ever repairable.

I'm surprised that you're not higher in voltage by now, so maybe some caution is worthwhile. Your 1 A charging is still fine; that won't hurt anything.

But wait! Isn't your charger a 12V CC/CV lab supply? In that case, I think you just need to switch to something higher in voltage. Just keep the voltage under 14.1 V.

The + and - plates will be grey and brown once it is fully charged. When it is discharged, they will both be grey. Don't be fooled by the paper separator in there. You'll know you're done with the reversal of the discharged state when half of the plates have turned brown.

The color change won't occur uniformly. First you'll see brown peaking out from under the grey, they just grey flakes on the brown, then all brown.

Wish I knew. ;-)

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----------------------------------------------- Jim Adney snipped-for-privacy@vwtype3.org Madison, WI 53711 USA

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I always disconnect it for overnight. It has been reading 12.0 volts the last two mornings.

Well, it's more like 32 amp hours. The built in hygrometer is starting to show green, so it is progressing. I can wait it out, no problem ;)

I was wrong about the supply. It is 12 volts nominal, but you can dial it up higher. To push 1 amp into it, the open circuit voltage is 14. But when loaded onto the battery, it is rock solid at 12.0 volts.

Okay, good. This looks just fine and "normal" so far.

Okay, completely normal progress. Exactly what you want to see.

That's just the battery loading it down. Also perfectly normal for a current limiting supply.

Whatever you did to this battery didn't seem to hurt it, but you REALLY pulled it down flat. That's actually pretty hard to do, but you're doing exactly the right thing to recover it.

At this point, I don't think you could do any harm by just leaving it connected 24/7. You're only putting 12 Watts into it, with the potential of going up to 14 Watts. That's not enough power to do any harm under any circumstances.

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----------------------------------------------- Jim Adney snipped-for-privacy@vwtype3.org Madison, WI 53711 USA

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All done, recharge was successful. It was on a slow 1 amp charge for 7 days. On the last day, it seemed to be completely charged. I could not push any more current into it. Raising the voltage merely caused bubbles due to electrolysis (at around 14.5 volts as several had said).

Reconnected the battery, and it cranked up strongly. Maybe more strongly than before the incident ;) Took it on several more drives, same result. I'll occasionally measure the voltage while cranking, that seems like the best way to measure actual condition.

Thanks to all.

Jim Adney wrote in news: snipped-for-privacy@4ax.com:

Anything that isn't red or black. I hate the red stuff, since when I'm trying to jump a battery and only have a crappy flashlight handy, the last thing I need is two red terminals on the same battery.