I also have a charging line running from the coach through the 9 pin umbilical which wasn't supplying enough amps to do any good. I put an RVi DC-DC charger on the toad and switched the charging line to the house (solar charged) batteries. After I did that, I had one instance of a dead battery, but after turning off the key and letting it sit for a few minutes while I hooked up, the battery charged enough to start the car. I figured out that all my battery issues were because I forgot to turn off the radio screen.