bad bad battery manu [RE-wrenches]

[Bruce Geddes]

Hi all,
            My limited understanding of lead acid batteries leads me to
think that if these batteries are failing after a short time from this cause
there is a charging problem.  Windy's comments are correct.

> It is common for positive posts to bulge in batteries that have been
> overdischarged many times, or maintained in a very low state of
> charge for long periods. The cause is swelling of the positive
> plates. (They swell out laterally as well.)
>
> Normally, the battery is designed to accommodate this phenomenon to
> the point where the battery becomes useless, without danger of
> breaking the case.
>
> Windy
>

Positive plate expansion is caused by the oxidising reaction that takes
place on these plates and leads to the swelling in all directions.  Long (?)
term over discharging and overcharging accelerate the process.  I very much
doubt that this would be caused by a buildup of debris, if it built up that
much it would short out to the adjacent negative plate and deactivate the
cell rather than push the positive plate up.  This debris is quite soft and
mushy.

I have seen broken cases on AGM cells from this but they were quite old and
the +ve grids were crumbling to pieces.  It was the tight packing of this
type that caused the cases to crack as debris can not fall out.  Most
flooded cells will have the cases bulging but not cracking.

Unless there is some very strange manufacturing fault I would be looking
very hard at the charge side and low battery disconnect settings.

Bruce Geddes
PowerOn

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