Wouldn't it also be helpful to place a diode in the charge wire to prevent any possible drain vehicle + side back to the RV?
I am saying this because I ran a wire from my main distribution panel, located near the rear of the MH, to the positive side of the CRV battery and had a dead battery when I got to my destination. Thinking this would keep the battery topped off I did not pull the radio fuse, as usual. The wire had +13.4 volts, measured at the destination point before attaching it to the battery. This wire was only 16 gauge, as I didn't expect it to provide more than a trickle and depended on the mechanical tow assembly carrying the ground side.
I still don't know why this failed.