2014 Ford Fusion Hybrid

From what I hear, these cars drain the starting battery fairly quickly when in accessory mode because of all the electronic things drawing current while being pulled down the highway. The solution for most people is to install a charge line, which connects power from your motorhome to your car's battery, usually through the 7/6-pin cable that you also use for turn signals, etc.. There are lots that you can buy that serve this purpose, or you can rig up something on your own if you're good with diodes, fuses, and such. I installed an Amazon-purchased one on my C-Max but haven't had much of a chance to use it yet. I forget what brand I got, but I think it was less than $50.