
I am not a battery expert, but from recent reading, a lead acid battery
will self discharge at a relatively high rate, and if stored in a discharged
state, will develop a condition I think is called sulfation.  In storage,
either the electrolyte should be removed and replaced for use (fat chance
I'd ever do that at home), or the battery should be stored on a trickle
charge.  I have also (I think) read that the condition may be reversable
if hooked up to a current limited charging circuit fro a LONG period of time.
The refernce I remember is to use C/50 (where C is the amp hours) as the
charging circuit, and leave it hooked up for weeks.  Some of this may
only apply to Gel type cells, but I suspect the same applies to the liquid
type.