Hi Kevin,
On our last RV (28' Triple E Class C) there was no battery disconnect switch and we found during storage, the phantom power was depleting the batteries.
We installed an On/Off Battery Switch ($40.00) in the battery compartment and the problem went away.
An easy DIY project - 1 switch and 1 additional battery cable. Can't remember if it was connected in the positive or negative line, but the instructions will say.
I also installed the same switch on my Son-in-law's 5th Wheel this past Summer and again, the dead battery problem went away.