I just installed a battery cutoff today. Marinco "Park Power 701" which retailed for $25. It's a fully self-contained keyed switch. So it can be installed on the outside of the battery box with no chance of sparking.
My X23b battery would be dead after 2 weeks of sitting. My guess is the antenna booster and other "small" items over that period of time was just too much. I installed it such that the emergency brakes and tow vehicle are NOT cutoff. Only the camper is interrupted.
That said, I'd like to ask a follow-up question: Is it safe to run the camper off of the internal power supply/charger provided by Jayco alone (ie without a battery)? Or is a battery required in the circuit?