I am going to have two amps. with 60 amps each. I want to have the cars regular battery left alone and im going to add a battery in the back of my car. I listen to my car with it off a lot because I park in a garage and i always kill my battery which I know isn't good. I don't know what size alternator I am going to get but how do you figure out what size battery isolator you need thanks in advance
