On Mon, 23 May 2005 13:30:27 GMT Ken Weitzel wrote:

Just off the top of my head, I suspect that at 50 ma's
he'd better start charging it now if you wants to use it
next winter

Yes, it will seem agonizingly slow, but it needs to be slow because
the lead sulfate can only be converted to lead as quickly as it will
go into solution, and the lead sulfate in a sulfated cell is much less
soluble than that in a freshly discharged cell (different crystal
structure.)

If you try to force the charging process, you'll just hydrolize water,
and this can damage the sintered plates if it happens too vigorously.

You don't want to "drive off" the lead sulfate, as that takes sulfate
ions out of circulation and just leads to buildup at the bottom of the
cell which will eventually short it out.

With patience, this will generally work if the only problem is
sulfation, which is what happens to a battery that is left in a
discharged state for a long time. The lead sulfate slowly converts to
a much less soluble crystal structure over time.

I've done this many times, but it doesn't always work. About half the
time you'll find that one or more of the cells are shorted and the
battery is only useful as a tradein.

I have never managed to restore a shorted cell.

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Jim Adney
Madison, WI 53711 USA
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