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Reviving 'dead' sealed lead acid batteries?

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aonomus

Sun Mar 29 2009, 05:36PM

Registered Member #1497 Joined: Thu May 22 2008, 05:24AM
Location: Toronto, Ontario, Canada
Posts: 801

So my parents have handed me a (heavy) box of SLA batteries from UPS's, and if I revive them they will be thankful. We've already tried a commercial 'reconditioner' meant for SLA batteries (has several operating modes) and with minimal effect.... Most of the batteries measure 2 or 4V, meaning most of the cells are shorted out with only 1 or 2 being still good. The conditioner appears to only apply 12 to 14V with an unknown frequency to the battery, which brings me to this next step...

- Would it be possible to use the same high voltage pulse method that has been shown to work with NiCd batteries (ie: discharge a photoflash cap into a battery) on a SLA battery?
- What would the effect of a small HV pulse be on the good cells vs the bad cells?
- What about lower voltage high current pulses (eg: intermittent 12V at 200A at a higher frequency like

)

Arcstarter

Sun Mar 29 2009, 06:22PM

Registered Member #1225 Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253

I am not trying to do any thread hijacking, but i also have some fairly large SLA batteries. The one i am trying to revive came out of an electric scooter, and is now going to be used in a gas powered scooter for the starter. I need a battery that is very dead to in the end be able to supply around 20-50 amps for a few seconds at a time. The battery is 7AH iirc.

Dr. Dark Current

Sun Mar 29 2009, 06:51PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

Someone told me that when the batteries are dead, they are dead and nothing can be done with that, as the electrodes are eaten away.
Also, when the batteries are found in a condition so that their terminal voltage is below ~10V, you can just as well throw them away.

Proud Mary

Sun Mar 29 2009, 08:33PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

There are thirteen different failure modes for lead-acid accumulators, and if a single procedure could correct them all it would long ago have become a patented feature of lead-acid technology. Put them in the safe recycle bin.

Carbon_Rod

Mon Mar 30 2009, 05:51AM

Registered Member #65 Joined: Thu Feb 09 2006, 06:43AM
Location:
Posts: 1155

Indeed, Harry has the right solution...

if you want to know what is done in 3rd world countries:

1. Uncap cells and drain the Pb particulates and acid
2. Unseal the battery cell lid exposing the battery electrodes
3. Wash off the electrodes and toxic reservoir Pb sludge with rain water
4. If plates are still intact chemical strip, reassemble separators, and reseal cells
5. re-flood cells with new electrolyte
6. Recharge cells
7. Dispose of toxic sludge....

Most poor people around such a facility have never seen an MSDS, and can't read the warning label in another language. Neurological problems are quite common for the kids and adults.

In North America people pay $5 to recycle such batteries as it is illegal to put them in the bin.

kell

Wed Apr 01 2009, 07:08PM

Registered Member #142 Joined: Sat Feb 11 2006, 01:19PM
Location:
Posts: 102

If you had a flooded electrolyte battery that was just getting tired from sulfation, it would be worth trying to bring it back. And the sealed batteries that people call "gel" cells (mostly actually absorbed glass mat or "AGM" nowadays) are supposed to be harder to revive. But for batteries as far gone as yours, it's probably not even worth trying. You're talking about real damage, not just aging.
But since you are interested in the subject of reviving batteries, check out this desulfation forum:

aonomus

Sat Jul 18 2009, 12:51AM

Registered Member #1497 Joined: Thu May 22 2008, 05:24AM
Location: Toronto, Ontario, Canada
Posts: 801

So just as an update, today I popped the covers off the tops of the batteries, opened the cells (removed the rubber valve) and found all the cells to be bone dry. Upon some further research and common sense, after years in float charge mode, all the water has been electrolyzed off.

Taking a syringe and refilling all the cells to a happy amount of liquid seems to have remedied at least one cell, and it is now taking charge (slowly, as the acid in the glass matt mixes with the water).

The fact that the cells were actually dried out makes some sense as to why using a desulfator did not help the condition of the cells, as they were simply dried out and had nothing to conduct electricity. Now as the water mixes with acid and the sulfate is being removed from the plates its able to charge with an actual current.

Edit: Another interesting discovery is that when the battery is *this* badly drained, the cell closest to the -ve connection feels more voltage and is more prone to electrolyzing the water and venting. What probably should be done is charge at a reasonable rate (0.07C from what I've found empirically) and then verify all the cells are fine liquid wise, re-seal the lid, and then desulfate just to be certain.

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