Our fifth wheel towed by F350 dual alternators had a 20 amp cartridge type fuse. It was charging or keeping the batteries in the fifth wheel charged and the refrigerator freezer was getting electricity..through the batteries. I hadn't thought about it but it did have a converter charger in it. The factory sent me a second vented battery box an cables. It was a Holiday Rambler Alumiscape. It had two 12 volt deep cycle maintenance free batteries.
Most of the wiring harnesses offered for connection between Fifth wheel or Trailer and the tow vehicle are really inadequate. I bought a heavy 10 gauge wired plug and leads Trucks and Trailers and soldered the connections and heavy shrinked them too. No way the flimsy 14 gauge wires on most would carry the 20 amp rated fuse load, imo.
if you don't have the capacity in your towed RV simple enough to buy the converter charger and wire it and..be sure to use battery boxes and vent hoses to the outside.
