[EVDL List]

Want to ask the list for some help.
I have a 12V battery of which one cell has been reversed
(likely multiple times) because it was the first thing to go
when the rest of the cells were still going strong.

I drilled a hole in the top of this battery and found that
one cell was going to 0V while the others were still above 2.1V
under 30A load, so the inverter (which I used to test it) did
not cut off its load (10.5V LVD) before that first cell was
entirely reversed and started in the negative voltages.

I have tried watering that cell and recharging it separately
but it looks like it does not hold much charge, therefor it
goes flat as the first of battery.
Is there anything that I can try to regain capacity?
This is an AGM battery and I went as far as squirting enough
water in the cell that it became a flooded cell (which I am
now converting back to AGM by continuous over-charging at
a slow pace so the redundant water will dissolve as H2 and O2
gasses.
All of my actions have shown a reduction of capacity or at best
no effect, so I am either going to toss it (likely first saw it
open to inspect it and see if I can find why its capacity has
been so reduced) or need to find a means to restore it to
useful capacity.
(I hate to toss anything that should not be halfway its useful
life by now)

Any suggestions appreciated.

Cor van de Water
Systems Architect
Proxim Wireless Corporation http://www.proxim.com
Email: [email protected] Private: http://www.cvandewater.com
Skype: cor_van_de_water IM: [email protected]
Tel: +1 408 542 5225 VoIP: +31 20 3987567 FWD# 25925
Fax: +1 408 731 3675 eFAX: +31-87-784-1130
Second Life: www.secondlife.com/?u=3b42cb3f4ae249319edb487991c30acb

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[EVDL List]

Cor van de Water wrote:
> Want to ask the list for some help.
> I have a 12V battery of which one cell has been reversed
> (likely multiple times) because it was the first thing to go
> when the rest of the cells were still going strong.

There isn't anything that will restore its original capacity, except
melting it down and remanufacturing it. About the best you can do is
what you've already done -- recharge it in the correct direction, and
give it a very long hard equalization charge (which helps the bad cell a
little but damages the good cells a lot). At best, this might get it up
to 25%-50% of its original capacity.

One "cheap John" option is to short out the bad cell, so you can use the
rest as a 10v battery. I've done this by driving a bunch of stainless
steel screws into the bad cell. Also drain the acid if at all possible,
to eliminate corrosion.

--
Ring the bells that still can ring
Forget the perfect offering
There is a crack in everything
That's how the light gets in -- Leonard Cohen
--
Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart_at_earthlink.net

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[EVDL List]

>
> -----Original Message-----
> From: [email protected] [mailto:[email protected]] On
> Behalf Of Lee Hart
> Sent: Saturday, October 06, 2007 6:20 PM
> To: Electric Vehicle Discussion List
> Subject: Re: [EVDL] Bringing a reversed battery back to life?
>

> Cor van de Water wrote:
>> Want to ask the list for some help.
>> I have a 12V battery of which one cell has been reversed
>> (likely multiple times) because it was the first thing to go
>> when the rest of the cells were still going strong.
>
> There isn't anything that will restore its original capacity, except
> melting it down and remanufacturing it. About the best you can do is
> what you've already done -- recharge it in the correct direction, and
> give it a very long hard equalization charge (which helps the bad cell a
>
> little but damages the good cells a lot). At best, this might get it up
> to 25%-50% of its original capacity.
>
> One "cheap John" option is to short out the bad cell, so you can use the
>
> rest as a 10v battery. I've done this by driving a bunch of stainless
> steel screws into the bad cell. Also drain the acid if at all possible,
> to eliminate corrosion.
>
> --
> Ring the bells that still can ring
> Forget the perfect offering
> There is a crack in everything
> That's how the light gets in -- Leonard Cohen
>


Lee,

>From this it sounds as if you may have glossed over the part where he mentioned that he had access to the individual cells.

Would you suggest charging the one cell with a long slow charge, or smoke it into submission.

I personally would open the vent and let it rip; In the hopes that a severe overcurrent would in some way perhaps breakup/burn-up the larger sulfate crystals. You can probably tell, I'm not a chemist. ;-)

I have a few batteries in the same condition..... some day, I'll try both of these methods

Do you know of a way to "open" a shorted cell? Assume I have isolated electrical access to the cell in question.

--
Stay Charged!
Hump
I-5, Blossvale NY

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