I have zip electrical expertise, but I do plan to add an isolator switch for me, even with only one battery. I think that if you can isolate your battery completely from your electrical system, you may save the batt from some slow discharge due to small leakage from the whole electrical system while sitting, not running. But more importantly, I would like to be able to disconnect my battery in emergency... Once a wire bracket holding a rubber cased fuse connection in my outboard wore through the rubber casing and shorted to ground. It came close to causing some damage. My bud sacrificed some pain to pull it off. It also bugs me to think that if my main power cables from the battery shorted to eachother , they are too near my plastic fuel tanks. If I smelled burning plastic wire casing, I could turn the switch to off and prevent further heat from melting into my plastic tanks. It is just something I think every time I see the tanks.