Being a mech engineer I had to jump in on this, first off all you guys are way over the top, batteries cost about 70 dollars a pop, I run two with a standard perko switch, this is about 140 in batteries. I spend more than that in fuel on any given trip, what the heck are you worried about. Also I agree with jaws, your not going to mess up the alternator unless you turn the switch hot. End conclusion buy new ones when they crap out.