Originally Posted by NJKris
Maybe goes to 'solar on the side' connector?
The year make and model of your rig makes it easier for us to second guess.
But I'm with everybody else it's either a dealer installed accessory like the tongue jack or for that matter possibly factory installed tongue jack or auxiliary solar input.
As long as it's good gauge wire fuse appropriately, if it ain't broken don't fix it.
The shop for your battery monitor has to go from the negative side of the batteries before anything else touches that negative side and then on the far side of that shunt your frame ground your solar negative you're any other negative that's coming anywhere near those batteries goes on me far side of the shunt away from the battery. And the shunt will want a little 12 + volt input with a little red wire that came with mine. That can go straight to the battery or any other point where there's 12 volt + continuously