[f6bits]

I don’t think the trailer battery has anything to do with the brake controller. I base this on the fact that my TV, and hence, the 7-pin connector, has the one wire that goes to the brakes. My brake controller tells me how many amps it’s sending to the trailer brakes, so it’s getting this from the wire that feeds the brakes, not a wire that’s getting input from the battery.

You *do* need some battery charge for the breakaway brake system, but that gets charged via the AUX pin on the trailer plug, and I don’t think the brake controller has any insight into that circuit…unless perhaps it’s a fancy factory-installed controller that’s integrated into the TV’s electrical system.