When I got out of the Army my neighbor gave me a 6 volt battery he had laying on the garage floor. I stuck it in my 1949 Chevy 1 1/2 ton truck, which I didn't drive too much. I really mistreated that battery by letting it go dead, then putting a charger on it when I wanted to use the truck again. I got 12 years out of that battery before it finally gave up the ghost. Turns out it was an Interstate 6 volt battery, which amazed me because I've always had the worst luck with Interstate 12 volt batteries. When I worked at the junk yard I'd pull batteries out of the cars coming in, put them on the charger, and sell the usable ones. Had the best luck with Sears Diehards, and the worst luck with Interstate, but this was all 12 volt batteries.