We have a 2013 C-Max Energi SEL that we have towed about 8,000 miles last year. We are getting ready to start out again this year. We have never had the Service Advance Trac light come on. We DO leave the car in ACCESSORY mode as per our owner's manual. We do this by starting the car normally, then shift to Drive, then to Neutral. We then press the ON/OFF button to turn the car OFF. We wait about 10 seconds and then Without Stepping on the Brake press the ON/OFF button again, which puts the car into Accessory Mode.
They battery will drain and go dead without a charge line from the coach. We installed a Brake Buddy Towed Vehicle Battery Maintainer: http://smile.amazon.com/BrakeBuddy-39332-Vehicle-Battery-Maintainer/dp/B004RCXB8A/ref=sr_1_1?ie=UTF8&qid=1434658212&sr=8-1&keywords=brake+buddy+charge&pebp=1434658220829&perid=1W9SBNE04KGQ4EKQ98PC
It has great reviews, but doesn't seem to work for us. I am in the process of testing whether the terminals I have it connected to for jump starting the car become disabled after several hours in ACC mode. If not, then ours is fautly and I will be buying a RVi brake Towed Battery Charger because it looks more substantial and at least has an indicator on it to show it is working. The Toad Charge looks good too, but is expensive and they seem to have made it more complicated by wanting you to run a separate harness to the car.
