12V power issue and solar ideas

[mikegascon1]

I am having a very similar issue as another thread on here but I didn't want to jump into their conversation.
I will figure out how to add info to my signature soon. Until then, here is my trailer info.
2007 3124 KB I think. Couch on street side and a comfy chair on the curb side.

The trailer is brand new to me. So, I don't know the history at all. The person that sold it to me showed me most everything while plugged in. It did not occur to me to check while on battery power only. I got it home, 250 miles later and I am thrilled with it. Now time to learn some things.
Most all lights worked on shore power. I assume I have a bulb out here or there. I unplugged shore power and nothing works except the electric jack. I tried, all lights, water pump, even the gauge under the sink and nothing came on. It is now closed so I can go get new tires tomorrow. I will check all fuses tomorrow. Could it be a dead battery? I checked the voltage at 11.1. But the jack works. Slowly, but it did work. It is wired direct to the battery. Wouldn't at least the lights for the water tank light with a low battery?
I did check the breakers and all were on. Other than the fuses next to the breakers, is there anything else to check? Note, I did confirm the switch by the tub was pushed down.
Another note is that I hooked it to my truck and plugged in the 7 pin plug and noted a light at the front, that will be handy for hooking and unhooking in the dark will be handy, was on. That makes me think the trucks 12V system was powering that light.
Where is the converter? I have read of people upgrading theirs.

Subject 2 is also power related. I would really like to go with solar. As of now, I am thinking mounted panels but I keep waffling on that choice. For a person that is new to solar is this a wise choice? https://www.renogy.com/new-400-watt-...r-premium-kit/ I will need to do some measuring to see if the panels will fit on the rear.
I am a tech guy so I want a nice "control center" that I can see how much power I am using, battery level, how much I am getting from solar... I believe that is called the solar controller.
I have not loomed at battery prices yet but I am thinking of 6V golf cart. Can someone share a link to a battery box?

Do any of the experts in here see Amy problems with my choices? Any preference to another brand? I like the kit idea so I don't miss anything. I am not apposed to piecing together a system but I would need a shopping list to do so.

Next question I assume is unique to 3124. What is the box on the rear of the trailer for? Just basic storage? It is just above the bumper, with an outside door. Not accessible from inside. Carpeted. Approx 2.5 ft tall, 2 ft wide and 1.5 ft deep. I do see a couple of wires in a bundle but I don't have any idea what that goes to

Lastly, a simple question. Is there such a thing as a bolt on 2 inch pipe for a receiver for bikes? Or, I guess I can borrow a welder and attach some square pipe.

If I need to break these questions out, I will. I am excited for the weather to improve in the PNW so I can get out there and learn more and eventually actually use it!

Thanks in advance
Mike

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