On the Dinghy Towing Forum, we're seeing that Ford recommends removing the "+" battery cable when towing several of their recent models behind a motor home.
Ford seems to have tried to standardize its systems beginning 1990's, So, I find it a little hard to believe that a disconnect will cause such grief.
A "memory saver" (like the 9V battery kits mentioned above clearly will NOT solve the problem of the battery running down. If a phantom load is running a starting battery down, a 9V won't last more than a few minutes.
Interestingly, some manufacturers recommend AGAINST a memory saver. So let me say this and hide behind a rock:
WHAT does the Owner Manual Say? I'd see if there was any comment in Maintenance, Battery, Towing, and Recreational Towing...
