So did you Not run it underneath to the battery, or how did you run it to that box? Over or under truck.Yes I installed one with my new 3500 Longhorn. Works well. Only challenge was that the bed of the truck, at least the rails, don't seem to be perfectly square. So had to adjust position to get it to work. Not a problem with the Retrax itself and would have come up regardless of cover brand. For power I tapped into the camper/5th wheel plug on the sidewall. Mounted a set of Yakima bars and bike rack.
Thank you..Pulled wire from the hole on the inside of the drivers wall of the bed, hole is by the front stake pocket. Removed the screws to pull out the 7 pin connector. Fished wire down on the inside of the wheel well and then back up to the hole by the stake pocket. Zip tied in place to a couple of the support brackets. T splices to the power and ground wire on the 7 pin. Power is always on to the 7 pin.
I finally did the same on my 2500 until my 3500 comes in to protect 5th wheel hitch. Does yours slide in and out smooth like constant power or does it kinda bog down some?? Can you send a video??Thank you..