I have a dual battery Diesel Ram Cummins( 98). I have it wired fore and aft for winch operation that I can insert the winch onto a receiver hitch on either end. To operate the winch,I have a switch inside the cab that energizes a relay that opens a contact so that the winch connector has power. I plan to charge this battery when it needs it by activating that switch and I have a copper jumper cable coming from the winch connector to the battery.
In the cold months, you don't want to be drawing on the dual battery system for the diesel that is critical to getting it started.
Look into a 2 bank charger which will maintain both batteries.
