Bought a new 6 volt battery for the Murdercycle. Old one dropped a few cells. Hot and cold weather abuse kills em quick. I've tossed them in the bike and kicked it over, and let the bike charge it up? If this is a bad idea, I need to get a multi-charger that does 6V at no more than 2 amps , per the manufacturer. Any big box store sell a cheap, adequate one?