This is a typical 30AMP Trailer wiring configuration using both 120VAC Appliances and 12VDC items.

My POPUP trailer is configured for OFF-ROAD Camping off the batteries. I have 255AH battery bank and our game plan is to camp off the power grid and run all the 120VAC Appliances and 12VDC items we want to run in a one day/night camping run. Then at 8AM the next morning we will re-charge our battery bank using a small 2K Honda type generator to get our battery bank back up to its 90% charge state so we can do all this all over again the next day/night run off the batteries.
You see a couple of extension cords running from my trailer here in the off-grid location...

My off-road POPUP Trailer also makes a very nice 120VAC POWER PLANT during those times when the county power grid is off line. We just run a couple of extension cords from the trailer into the house and run off the trailer batteries. Gives us some lights and HDTV to watch. House has wood burning fireplace so we keep warm...
Neat to have around...
Roy Ken