I have a 2014 Focus, and they say to remove the NEG cable. But read that if you just add a charge line to the car from the motorhome you don't need to do this.
I have asked why from Ford and they don't know why. Does anyone know what the reason is? and if you need to do it anyway?
Also, the neg cable is easy to remove as it is just a bolt on the frame right in front of you above the battery. It is best to get a marine battery shut off switch (about 25 dollars) and put it in line with the cable and then you never have to use any tools just switch it off and on as needed. It will sit right on the cover of the battery. I sure would like to know what the best way is and not have to run 12V to the inside for a brake unit as if the cable is off, the 12v plug is dead.
Thanks,
Bob