Adding mppt controller 16' Bambi

[Sport 16 STL]

Looking for answers, as always. I have a 2018 16' Bambi with 2 solar panels on the roof and a homemade 200 watt suitcase. Recently changed out the controller for a Renogy mppt. While my head was in the hole, messing with the wiring, I found a wire under the battery cables that I hadn't seen before. It is yellow, with a solar label, and a telephone type plug on the end. I have already identified the yellow and green cables coming from the solar.
Pictures below of the cable and a distribution box that I haven't figured out. I have a 12 volt positive and negative bus bars but is this box 120v?
Thanks

[BayouBiker]

it is a communications cable for a remote display panel that you may or may not have

[Malia20]

The yellow wire is for solar controllers that have a remote display. The other end of the wire is in a wall somewhere (probably varies by model. My 20's is in the galley near the pump switch/battery monitor). Your Renology may or may not be able to use it.
The black junction box you have opened up is for your 7-way cable for the hitch (turn signals, brake controller, charging, etc). If you have a need to replace your 7-way cable you could disconnect it here and pull it out of the A-frame. This is easier than splicing the wires or chasing them down through out the rig.
Good luck!
Fred

[Sport 16 STL]

Thanks, I assumed it was for some type of communication cable. The other end is probably behind the gauges and pump switch console. Will help if I get a battery monitor like a victron.
Also thanks in the 7 way wiring box.