Can you just put a 50lb tool box (or other heavy item ) in the drivers seat to keep the 7pin going?
Tangentially related: I was thinking about if you have a toy hauler with a 48v golf cart. 8- 200 amp-hr @ 6v batteries hold around 10kwh...or about 5kwh usable power. Compared to your typical RV battery bank (even a lot of boondocker battery banks), that's pretty massive. If you do find your RV battery bank low and you aren't planning to depart, it could be a good source of power to get thru an extra few days.
A 48v DC to 12v DC converter should be fairly simple to wire up and would give you a backup battery source.
