Recovering UPS batteries

[Th3_uN1Qu3]

I picked up a pair of UPS batteries today for $4. They are spec'd at 12v, 7.2Ah and made by "Kung Long Batteries Industrial Co Ltd". One of them is good, the other collapses under load. But i find it interesting that both charge at a ridiculously slow rate - 400ish mA. I've charged cellphone batteries with more current!

The current increases only if i increase the voltage beyond what is safe for those batteries - they need 16-17v to really get going. At this level i hear gas forming, and AFAIK if the cells are gassing it means they are good. I don't want to fill my floor with acid however.

I've read about pulsed charging restoring sulfated cells to useful life, so i dug out an old AT power supply (they are stupid easy to mod), and made it into a ghetto pulsed charger. I removed the 12v output capacitor, this oughta make enough pulse. I tried to jump the inductor as well but the PSU didn't like it - on AT PSUs the TL494 is fed from the 12v rail. With just the capacitor removed things work fine because the batteries themselves are acting like a huge cap.

I also wired a pot between the positive input of the TL494 error amplifier and ground, so i can set the voltage to whatever i like. Btw, on this particular supply the second error amp isn't even used - the 12v and 5v are resistively summed then sent to error amp 1. Group regulation at its best.

I set it so that the weaker battery doesn't exceed 14.8v, and let it do its thing. I noticed that the current increases briefly if the batteries have been put under load then immediately connected to the charger. This is reminiscent of NiCDs and NiMHs that had grown crystals - i used to zap those with a 100uF capacitor charged to 250 volts and they would start charging afterwards. But at the size of those batteries i'm not sure how much that would help.

I'll be letting them charge overnight and see what happens, trickle charging never hurt anything. Now i'm looking for an UPS to drop them in.

[Bubbanacious]

Re: Recovering UPS batteries

I picked up a pair of UPS batteries today for $4. They are spec'd at 12v, 7.2Ah and made by "Kung Long Batteries Industrial Co Ltd". One of them is good, the other collapses under load. But i find it interesting that both charge at a ridiculously slow rate - 400ish mA. I've charged cellphone batteries with more current!

The current increases only if i increase the voltage beyond what is safe for those batteries - they need 16-17v to really get going. At this level i hear gas forming, and AFAIK if the cells are gassing it means they are good. I don't want to fill my floor with acid however.

I've read about pulsed charging restoring sulfated cells to useful life, so i dug out an old AT power supply (they are stupid easy to mod), and made it into a ghetto pulsed charger. I removed the 12v output capacitor, this oughta make enough pulse. I tried to jump the inductor as well but the PSU didn't like it - on AT PSUs the TL494 is fed from the 12v rail. With just the capacitor removed things work fine because the batteries themselves are acting like a huge cap.

I also wired a pot between the positive input of the TL494 error amplifier and ground, so i can set the voltage to whatever i like. Btw, on this particular supply the second error amp isn't even used - the 12v and 5v are resistively summed then sent to error amp 1. Group regulation at its best.

I set it so that the weaker battery doesn't exceed 14.8v, and let it do its thing. I noticed that the current increases briefly if the batteries have been put under load then immediately connected to the charger. This is reminiscent of NiCDs and NiMHs that had grown crystals - i used to zap those with a 100uF capacitor charged to 250 volts and they would start charging afterwards. But at the size of those batteries i'm not sure how much that would help.

I'll be letting them charge overnight and see what happens, trickle charging never hurt anything. Now i'm looking for an UPS to drop them in.

Why not just buy new 12v 7.2ah's that will work for 5 years? They're not that expensive! Fixing old batteries is not so effective..

[Th3_uN1Qu3]

Re: Recovering UPS batteries

Why not just buy new 12v 7.2ah's that will work for 5 years? They're not that expensive! Fixing old batteries is not so effective..

True, they're quite cheap. But are they actually guaranteed to work 5 years? More like 2.

[Bubbanacious]

Re: Recovering UPS batteries

True, they're quite cheap. But are they actually guaranteed to work 5 years? More like 2.

So it's basically like this in the battery market:


1yr life batteries
- cheapest
- not labeled one year for obvious reasons
- with no load and use, can last up to 2 years

3-5yr life batteries
- More expensive, higher end of the market
- with small load and casual use will surpass 5yrs if good quality brand

10yr life batteries
- double the price of the 3-5yr batteries
- hard to justify cause most equipment will be garbage within 10 yrs


- Basically if you buy a dirt cheap battery you're getting the 1 year life cycle battery. They're not labeled that and the vendors get away selling junk. This all happened because the lead prices shot up 2 years back. Good vendors paid more for their batteries, crap vendors sank to selling junk batteries.

[Phaihn]

Re: Recovering UPS batteries

Speaking of UPS batterys i have one i dont know if its any good still i think its dead idk too bad i recycled the rest of the UPS unit.

[kc8adu]

Re: Recovering UPS batteries

those sound like junk.waste of time.
i just set up external batteries on the ups.helps i get 6 month old pulls from wheelchairs.

[cadillacman]

Re: Recovering UPS batteries

i have a ups on my fisht tank.. sounds dumb but ive dealt eith then dying a few times because of power outtages.


I have a old apc ups. It aso uses a 12v battery. I removed it and ran some wires with 25a fuises on each end.


I then out a marine deep cycle battery in a battery box and hooked it up.

works perfect, and the ups will run for days if the power goes out.

[japlytic]

Re: Recovering UPS batteries

You can't rejuvenate sealed lead-acid batteries with a battery zapper - it only works on flodded lead-acid batteries, such as those used in cars.
The charging and minimum voltage (at 'discharged' state) characteristics of flodded and sealed lead-acid batteries are different.
Remember that some UPS units have the battery connected to the mains side as well.

[Th3_uN1Qu3]

Re: Recovering UPS batteries

I found out sealed lead acid batteries aren't that sealed so i proceeded at prying the cover apart on the bad battery and adding some water to the cells.

Except for spilling mildly acidic water everywhere, i didn't achieve much. It only brought to my visual what i already knew - this battery has a dud cell. I left the rubber caps off so that excess water can boil, and while its five friends happily bubble away, there is one cell which just sits there looking at me. Not much that can be done about it i'm afraid.

[Th3_uN1Qu3]

Re: Recovering UPS batteries

Ah, edit time expired. I have news - i am now the owner of a Properly Shorted Battery (tm).

Since with the vent caps off i would easily notice activity before the thing would spit acid at me, i cranked up the power. The bad cell did start gassing a little, but at this point i was boiling the crap out of the others already. Then something happened but in the opposite direction of what i had expected - the current suddenly shot up, the activity in the bad cell ceased entirely, and the other 5 started boiling even harder. I immediately disconnected the charger.

Put under load, it sits steady at 10.2 volts. Before, it would drop down to 8.5... Current capability is also adequate now, and charging to 11 volts it seems happy. No more boiling on any of the cells and a healthy 2A of current going in. For what i'll be doing with those two batteries, it won't matter if it's 24 or 21 volts nominal... if they deliver enough current this way they're gonna be fine.