A comment. the above is good stuff.
from experience i have learned this stuff that might prove usefull.
Lead acid batteries go to heck if they dont STAY charged too, something about them "sulfating", like i care what it is called, i just realized to late, that letting my car battery drift down was killing it. (i dont drive much for the "environment")
SO
add to the horrible charge/discharge life of a Lead Acid, and tack on the death from staying discharged to it :-( and prefer that the battery be charged, you know in that fantasy world :-)
now that i keep the LA batteries charged properly i am getting MANY more years out of them, then the former stupid way i dealt with them.
some gell cell info i learned (also the hard way)
overcharging these creatures causes bubbles in the darn gel (electrolyte) and they never leave. and the further you discharge them (or any LA) the less cycles you get, as bad as 20 cycles for full discharges.
so with gell cells the same thing is true, you want to keep them charged, and the charge control is even more important (bubbles).
then i learned (i did not want to know) that they ship the lead and acid off to 3rd world countries to "recycle" the materials. it was a few years ago, but they showed this village living in its usual squaler conditions, with a acid creek and lead lined children. it was not a good thing to do to people.
i just thought i would comment, this stuff ALL sucks, NIMHY and LI-ION are much more expencive, but they love to be discharged and charged.
there really is no totally practical way to store human type energies, without caveats.