Is this wise ?

[nate6472]

I have a primary and secondary battery, connected by a manual transfer switch. They are connected except when the rover is off. The secondary powers lighting and keeps the primary from loosing power for starting. Can using two batteries when starting and running damage anything? Thanks in advance

[mongoswede]

I assume you have them wired in Parallel? As long as they are wired correctly there should be no damage. If they are connected when the truck is running then the charging system just sees one battery. A setup like this is handy for high electrical loads associated with lots of accessories or things like winches.

[nate6472]

The secondary ground is connected to the primary ground. The secondary positive connects to several devices, including winch, and to the primary positive via a marine battery cut off/on switch.