I read in Motor Home magazine a few months ago about someone having a problem with excessive battery drain while towing a MDX with navigation.. Can not find the article now, must have thrown it out, but it seems like the solution to this problem was to remove a fuse (maybe #25, not sure) when towing to disable the navigation system.
Long time since you posted this. Have you been towing your X yet?
I also tow my MDX behind my motor home, but use the "Brake Buddy" unit for braking the MDX while towing. Check out the "Brake Buddy" braking system. It works okay, but what I like most about it is that it requires absolutely no modifications to the MDX or to the motor home. I didn't bother to get the break-away part however. The break-away system requires you to drill a hole in the firewall of the MDX - something that I'd rather not do.
To protect the MDX from rocks, I custom installed two Class C size "Rock Solid" rock protectors under the motorhome. They spread the full 8 1/2 ft. and are overlapped to prevent leakage.
I figure that any pebble thrown up by a rear tire, must first pass under/around the standard truck mud flap, then travel 10 ft at 4 inches off the pavement to pass under the rock protectors, then rise up 18" to strike the MDX. Pretty long odds.
I concluded, the chances of getting dinged from my motorhome is so significantly less then the chances of getting dinged on the interstate by some other vehicle that I don't spend any time worrying.
Relative to the tow brake systems, the U.S. Gear System is harder to install, but I believe it's braking is more effective and controllable than the " Brake Buddy". The most attractive feature is that you don't have to hook anything up or disconnect anything when you hook up or disconnect the motorhome, it is always available.
Update On Fuse Removal To Tow MDX Behind Motorhome
Just received my September MotorHome magazine and it contained a letter from American Honda concerning Towing an MDX behind a motorhome. I thought removal of a fuse was only required on Navi equipped MDX"s but removal on non-Navi is required also as stated by American Honda as follows:
"To prevent battery discharge during motorhome towing, which requires that the ignition switch be in the Accessory position, the No. 9 fuse (also labeled Front Accessory Socket) in the passenger-side interior fuse box should be removed. This fuse powers the audio system, cigarette lighter, accessory sockets, multi-information display unit, Navigation display unit, rear ceiling light and rear map lights; it does not power the audio or Navi system memory, so no resetting of radio stations, etc. will be required. The fuse can be reached through a small access door on the passenger-side kick panel.
"This fuse should be removed even in a non-Navigation -system car, in order to deactivate the multi-information display. If an MDX customer requests any additional information, they should contact Acura Client Services at (800) 382-2238"