If your two batteries are producing 12volts each (check them individually), and the lead connecting them is going from positive on the forward battery to negative on the rear battery...you can;t have just 12 volts...it goes against the laws of physics.
I think you may have your batteries installed wrong. From the bumper back, negative post (to ground) on body, positive post connceted to negative post on next battery, positive post on 2nd battery to wiring harness etc. There are a few fuses right there, connected to the positive post. They look like cylinders or connectors.
I think you may have your batteries installed wrong. From the bumper back, negative post (to ground) on body, positive post connceted to negative post on next battery, positive post on 2nd battery to wiring harness etc. There are a few fuses right there, connected to the positive post. They look like cylinders or connectors.