I have a problem with my electrical system that is driving me crazy. I have a trunk mounted battery that show's 12.6 volts until I connect the positive and negative battery cables to it then the voltage increases to no end. I don't have to start the car but only connect the cables and turn ignition switch over to ignition 1. I thought it was the battery and replaced it with a new one only to experience this same phenomenon. The voltage will continue over 15 volts before removing the cables. After removing cables the batteries will subside after a couple hours and read normal voltage for a sitting battery. Again, this is my second battery and the engine isn't even running so I'm thinking it has to be in my wiring. I know this is a weird problem and I can't find a thing on the internet pertaining to it. Anything you can throw at me will be appreciated. Greg