When you park the TC, do you unplug the truck to camper 7 (or 6) pin?
I do to keep the truck's battery from running down (Chev truck, no isolation)
That leaves the TC 7-pin socket empty, So you could add a 7-pin type plug to the battery wires on the suitcase (pin 4 and ground only) and just plug the suitcase (which has the built-in controller) into that, which will then charge the TC battery in parallel with the other solar set.
Not ideal for distance from controller to battery, but you still get something from it.
