I am installing a car audio system very soon and I am purchasing items as I go. When it came to adding another battery due to the wattage of the system that I am installing I forgot how they should be wired. I have done this before and since I dont have the batteries in front of me at the moment I thought that I would post this. In other words should they be wired in series or parallel and what is the real purpose of the isolator in a dual battery system.