I get a battery every 2-3 years whether or not I want it. I think the way my car is wired with all the factory wiring and the aftermarket radio plus the 60amp alternator results in dead batteries. I want to put the larger battery and alternator on for harsh climates just in case I get all the electrics working.
My bike is weird, I think the battery is dying so every 2-3months I charge it 24hours and it still works.
