Discussion:
What is likely wrong with this battery
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T***@pobox.com
2015-01-24 16:17:40 UTC
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I have a 12v lead acid battery that was used in in a personal watercraft last summer with no problems. I maintain the battery when not in use with a Schumacher 1.5 amp battery charger/maintainer.

Last fall, when I needed to start the boat to put it away for the winter, I could not get the boat started without jumping from a car. It would barely crank over with its own battery.

After that I put the battery on the maintainer. After a month I checked the battery and the cell closest to the positive full was at the correct water level, but the other five cells were below the fill line, which is unusual for a month on the charger. I refilled those cells with distilled water, and then put the battery on a load of a single car headlight (55w) for a while, took it off for a while, and repeated back and forth until the light dimmed down some.

I then put the battery back on the charger/maintainer. After a couple of days the maintainer light had changed from yellow to green, indicating that it had taken the battery to full charge and was then in maintainer mode.

One month later I went to check the battery, and that first cell was still full, but all five other cells were essentially dry.

I've refilled the five cells with distilled water, and checked voltage, and it was at about 12.3 volts with no load. I put the headlight load on it, and voltage dropped to about 11.7 volts. I've not put the battery on the charger yet, pending any input I get here.

I'm thinking something catastrophic has happened to the battery, and I'm probably wasting my time. At the time I first had trouble with this particular battery, was at the end of its second season. Past experience is that I can get about 4 years out of a battery on this boat. Can anyone explain what might have happened, or offer any suggestions to try to save the battery?
John Henderson
2015-01-24 20:36:35 UTC
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Post by T***@pobox.com
One month later I went to check the battery, and that first cell was still full, but all five other cells were essentially dry.
The simplest explation is that the ful cell has an internal
short-circuit, caused by the accumulation of shedded plate material in
the space below the plates.

This is a common mode for the eventual failure of a battery. One cell
fails first, and the others soon follow.

The other five cells will be getting overcharged as the charger tries to
bring the overall battery voltage up to specification. This
overcharging will turn their electrolyte into hydrogen and oxygen which
will escape.

John
Terry Quinn
2015-01-25 04:21:36 UTC
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John,

Thanks for the reply. From what you describe, it doesn't sound like there is any way to repair it. Would you agree with that?

Terry
John Henderson
2015-01-25 13:17:09 UTC
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Post by Terry Quinn
Thanks for the reply. From what you describe, it doesn't sound like
there is any way to repair it. Would you agree with that?
You'd have to somehow remove the accumulated sludge from under the
plates. Even then, I think you'd soon have some other failure mode, or
similiar failure of the other cells.

Not worth trying to fix is my opinion.

John
Terry Quinn
2015-01-25 23:55:58 UTC
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Okay, thanks again. I'll just plan on buying another one in the spring when I need it.
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