Help, Ford Explore battery dies when flat towing

Good question Blownstang01, I guess because the manual says the key should be in the accessory position. I wonder why they would say that if it was not necessary.
Knowing that the manual said this the guy who wired the explorer to the motorhome did so in a way that the key has to be in the accessory position for the brake lights and turn signals on the explorer to work.