batteries

Hi - was wondering if anyone ever tried maintaining 2 batteries at once using a single battery tender? I have 2 car batteries each with at least 2 to 3 years of life left. I want to keep them sharp in case I need them for my generator. Could I hook up jumper wires from one battery to the other...

Hi, I need to get a new battery for my 2006 Yamaha FZ6. The dealer is going to charge me about $100 for the battery and $30 for labor. I'd rather save some money, buy the battery online and do the labor myself. Does anyone know any good batteries out there? Any good stores to buy them...