Battery rejuvenate

Bluntly :-

At 2 volts, and "removed from a UPS" they were probably already dead (overcharging, end of life) before they were killed again by leaving them discharged at such a ridiculously low voltage.

Your charger is a smart charger. Be smart. Take the hint. :)

Know anyone that needs some ballast?

Whenever I've had a "12v" battery fail like that, it's dropped to "10v" then "8V" then "6v" ... as one by one the cells die. They don't come back. No amount of injecting distilled water, or other popular "remedies" often more suited to flooded cells (including off the wall ideas like adding various alkalis ...) do much good.

Any fixes are low-reliability, short-duration, and not something to rely on. Ultimately, you'll find the cells bulging out of their case ... just scrap (recycle) them.

Water ? Your kidding right ?

KenW

[snip]

If, and that's a pretty big and unlikely if, the batteries can be restored to anything useful, you've got to try charging them up first.

Yeah, you hooked up a charger, but many of them are "smart units" that analyze the load (the battery)'s electrical characteristics to determine how much current to send across.

Since your batteries are dead, dead, dead (so to speak) with only 2 volts (probably less..), the chargers refuse to send any current across.

So... you've got to set up a "dumb" charger.

If you don't have one around, there are two simple ways to try:

a: find an old phone or similar wall wart charging block rated at 12V DC . Attach the wires to the battery and leave it on for ten hours.

Then measure again and try the smart charger.

b: use jumper cables from a known _good_ and _charged_ battery to feed the dead one. Then measure again, etc.

I've done this exact same procedure with, yes, dead UPS units.

In about 1/2 of the batteries I've been able to get them back up to some useful level of charge.

Note by "useful" I mean a fraction of the original, as I'm using these UPS'es for:

1: to filter out the 1/2 second glitches that would otherwise reset my tv and cable modem, requiring fifteen minutes (GRUMBLE!!) to come back up [a],

2: to give enough time to shut down whatever they're hooked to.

Every so often I get one that does, indeed, get close enough to original spec...

[a] plenty of those when, for example, a grid area 15 miles away goes dark or is turned back on...

I let a car sit too long with out starting and the battery was 'dead'. Smart charger would not charge it. Hooked up a dumb charger for a while and then the smart charger would work.

You're likely SOL on those batteries.

I have an old-school heavy duty 6/12/24V car battery charger. I'd hook that monster up to those batteries on full blast as a last resort, and just bake them. Don't over-bake, check the gauge. Worth a shot, I guess.

Well, there is all that. But consider the amount of energy within any sort of lead-acid battery, even a gel-cell. With all that in mind, while 'worth a shot', be sure to:

There is that. But, consider the amount of energy in any lead-acid battery, even one as 'slow' as a Gel-Cell. While 'worth a shot', be sure to:

a) Do it outside. Lots of hydrogen will be released if it works at all. b) Make sure that if anything lets loose (blows up), that the shrapnel will do no harm, or if it melts down, nothing will be damaged. c) Have the charger on a remote switch or some such so that one does not need to be standing nearby to turn it on or off - or, stand behind something. d) When finished with the process, give it time to cool down. e) All the while understanding that the actual chances of this working in any meaningful way are between slim and none.

Peter Wieck Melrose Park, PA

+1

Ok, here's my $.02 8-)

If they need to work well, replace them.

If you just want to play, here's what I'd try:

Get a dumb charger (I use a Schumacher with 2 and 6 amp ranges).

Get a tungsten filament bulb (I use an 1157 dual-filament auto taillamp bulb) for batteries of "normal" size, 2-20 amp-hour. Get a voltmeter that you trust, or can check against another similar battery.

Connect the voltmeter to the battery. Connect the negative side of the charger to the negative battery post. Connect the positive side of the charger to the base of the bulb. Identify the contacts on the bottom of the bulb, selecting the small filament for little batteries (~2 amp-hour) or the large filament for automotive-sized batteries and connect that terminal to the positive post of the battery. Set the charger to the upper, say 6 amp, range.

Get a sheet of notepaper, write down the time and the voltage, then turn on the charger and record both voltage and time over the next few hours. You'll have to decide how often, based on how fast the voltage changes.

What you're looking for is a fairly quick (hours) ramp to about 13 volts, a slow climb (days) to 14 volts and a leveling-off at less than 15 volts. If you see that pattern, the battery is taking a charge. If the voltage won't reach 13, turn up the charger or use the bigger filament. If the voltage goes over 15, turn down the charger or use the smaller filament.

Once the voltage has stabilized at 14-15 volts, let it stay there for a day, then disconnect the charger. Voltage should fall to

12.5-13.5 and stay in that range for a day. If it does, use the bulb as a test load and repeat the voltage/time measurement. An 1157 bulb passes about half an amp on the small filament and about 2 amps on the big filament, so that gives a crude measurement of capacity.

You might get 10% of rated capacity, most likely less.

Have fun,

bob prohaska