So today my Conntek 10110-048BX (7 pin wire harness with junction box) from Amzn came in ($32 or so). I cut a simple Hopkins 48185 18" extension in half and wired to the 7 junction box.. and also routed the wires to the battery box.. I also mounted for future brake option a breakaway switch incase I decide to add brakes to the unit down the line I will be ready.

The propane plate is mounted down with some 2" self tapping with washers and lock washers..

I put the breakaway on the passenger side.. near the battery box. 

The junction box is partially under the propane tray under the battery side as well.

I did get some wire 'loom' to tidy the wires up and clamp them to the frame tomorrow.

The battery box (Camco 55362 for group 24 batteries) is secured to the propane tray with some screws and lock-nuts as well. The nylon strap is basically just sitting there for now as I don't have a battery.

The purpose is to run the black (hot) wire to the junction box, then to the battery (in the box) that will receive a trickle charge while attached to the primary tow vehicle and also I ran a wire (as noted in prior post) into the trailer compartment for some 12v items.. I got some 10 AWG wire for this as its good for upto like 50 amps.. I know the water pump I am looking at only draws 1 amp.. so I should be good..