I Was Talking About This One Car That I Seen Where The Guy Had A Extra Battery In The Trunk In When The Car Would Die He Would Go Under The Car In Connect The Dead Battery To The Spare And Jump Start The Dead Battery Have Any Of You Heard Of This Before?
They keep the system battery and the starter battery electrically separate so you can play the system with the car off and not drain the starter battery. The result is even if your system battery is totally dead you can start the car, open the doors, etc... If that's not what you're looking for, then perhaps you'd better explain it better.