Ripnlips,
I don't know if you have finished your project yet, but this might help. There are to ways to hook up batteries(series circuit, parallel circuit) K S B has explained it right. All the systems I have installed I got a 50amp in line breaker in addition to what I got in the kit. (napa, schucks, etc.) make sure you get batteries that are specific for this, a standard battery won't last. Caution, make sure this is a completely independent system from the rest of your boat. Still sounds like you need a guest 2611 dual bank onboard charger with an ac adapter plug