Invisibrake not charging tow vehicle.

I've never heard of a braking system supplying charging to the tow vehicle. Powering the braking system directly from the motorhome and not the vehicle battery is inherently unsafe as the brake would not operate in a breakaway situation.

You need to install a direct charge line from your motorhome to you vehicle battery. You can either do this your self (be sure and add a fuse) or purchase a ToadCharge or a RVi Battery charging system. No more dead or nearly dead batteries.