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trendal
J♠



Registered: 04/17/01
Posts: 20,815
Loc: Ontario, Canada
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Sealed lead-acid batteries
#14563548 - 06/05/11 08:00 AM (12 years, 7 months ago) |
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I got my hands on a set of used UPS batteries, that I want to see if I can rejuvenate.
They are NPX-25 12V batteries, from EnerSys Inc.
All the batteries are extremely discharged, down to about 0.4 volts, and they still pass a fairly constant 70mA. The impedance of the batteries was too high to measure accurately, but was somewhere in the 100,000's. I figured the water level was low, so I added some distilled water to all cells on 2 of the batteries (10-11cc in each cell on one battery, the other only took 1-2cc per cell). Both batteries tested the exact same after a night of sitting.
I attempted to charge the batteries, with a wall wart rated at 12V and 800mA. The voltage goes up to about 14V at no current draw. I connected the charger expecting a little snap...but got nothing. The voltage with the charger attached is 14V, so I didn't expect much current...and sure enough it checked out at just 0.25mA.
Any ideas?
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Once, men turned their thinking over to machines in the hope that this would set them free. But that only permitted other men with machines to enslave them.
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argg
Stranger


Registered: 07/20/09
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Re: Sealed lead-acid batteries [Re: trendal]
#14563555 - 06/05/11 08:02 AM (12 years, 7 months ago) |
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crack them open and reprocess the lead and other items into new batteries. I think that is how the battery manufactures rejuvenate them at that point.
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SomeGuy
I feel better now :)


Registered: 04/18/10
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Re: Sealed lead-acid batteries [Re: trendal]
#14563562 - 06/05/11 08:07 AM (12 years, 7 months ago) |
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it sounds like you know more about batteries than I but it sounds like the acid has been neutralized, and the lead is probably ate up
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trendal
J♠



Registered: 04/17/01
Posts: 20,815
Loc: Ontario, Canada
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Re: Sealed lead-acid batteries [Re: SomeGuy]
#14563622 - 06/05/11 08:29 AM (12 years, 7 months ago) |
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Well I don't think the acid has been neutralized....I don't even see how that can happen in a sealed battery.
I was just playing around with one of the batteries. I hooked it up in reverse...and it started to draw a current of 800mA. The battery then tested at 4V reversed but that quickly dropped back to 0V. I then hooked the battery back up to the charger the right way...and it started taking a charge!! It's at about 7.5V and climbing.
WTF?
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Once, men turned their thinking over to machines in the hope that this would set them free. But that only permitted other men with machines to enslave them.
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SomeGuy
I feel better now :)


Registered: 04/18/10
Posts: 7,496
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Last seen: 9 years, 8 months
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Re: Sealed lead-acid batteries [Re: trendal]
#14563638 - 06/05/11 08:35 AM (12 years, 7 months ago) |
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the sulfuric acid reacts with the lead, releasing electrons, no? that's what I thought and how the acid would be neutralized. Reading what you just said, maybe the cathode was oxidized and by hooking it up backwards, you blew the oxidation off of it
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trendal
J♠



Registered: 04/17/01
Posts: 20,815
Loc: Ontario, Canada
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Re: Sealed lead-acid batteries [Re: SomeGuy]
#14563650 - 06/05/11 08:41 AM (12 years, 7 months ago) |
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Ahh, sorry, I see what you're saying now. The lead reacts with the sulfuric acid to create lead sulfide crystals.
I am quite sure that all the batteries are quite heavily sulfated, and plan on spending the next month desulfating them! However, I always thought that a sulfated battery would appear to take a full charge, but the charge wouldn't last very long.
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Once, men turned their thinking over to machines in the hope that this would set them free. But that only permitted other men with machines to enslave them.
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