In article , Bill Darden
writes

During the normal discharge process, soft lead sulfate crystals are
formed in the pores and on the surfaces of the positive and negative
plates inside a lead-acid battery. When a battery is left in a
discharged condition or is continually undercharged, some of the soft
lead sulfate is re-crystallizes into hard lead sulfate, which cannot
be reconverted during subsequent recharging.

Is there any way to recover a sealed (vented) accumulator once it has
been left partly charged? We've been given a mobility buggy for Sue and
one accumulator is OK but the other one won't fully recharge. I have a
three stage charger, the first accumulator goes through all three stages
but the second one sticks at stage two, and never gets to stage three.
I've bought a replacement, but wondered if there was anything I could do
with the old one - would a rapid discharge and recharge sort it out?

John
--
Jon Rouse