The batteries can stay connected while the rig is running, so that both batteries are charging off of the alternator and you have double the capacity while winching, etc. The system you probably want are something like what I have (although mine is custom with various parts) where a solenoid is controlled from the cab and you can manually connect or disconnect the two batteries or leave it so that the batteries connect and disconnect automatically, when the rig is turned on and off. It won't be as cheap as piecing it together from various parts and homemade, but might be easier in your situation. They can sell you a whole set up, wires and solenoid and everything.
