12V wiring Aluminum Cargo Trailer conversion

SlideInDad wrote:

DrewE wrote:

Assuming you have electric trailer breaks with a breakaway switch, the trailer chassis will have to be grounded for that system to work properly. (I guess that's also assuming you're using the house battery for the emergency braking power, which is standard practice. Having to maintain two separate batteries when one will do just fine on its own seems...well, silly.)

I do have a breakaway system with an old dead battery, was figuring on wiring it to the new 12V house battery system. I haven't looked yet but assumed it was grounded back to the Tow Vehicle?

The ground for the trailer brakes (and hence also the ground for the brake lights and whatnot) needs to be connected to the negative of the battery, and the positive from the battery goes to the breakaway switch, and the other side of the breakaway switch to the brake coils in parallel with the brake wire from the tow vehicle connection. The ground connection can't go back all the way through the tow vehicle, of course, since the whole point is to activate the trailer brakes should the trailer and tow vehicle become separated from each other. It is shared with whatever ground is there from the tow vehicle connection, which I think might be what you meant.

I did a tiny bit of research, and apparently the accepted best practice for aluminum trailers is to run ground wires to the brakes and lights and still bond the frame to the ground connection from the tow vehicle. The bonding among other things helps prevent static buildup (I assume mainly from the tires rolling down the road). Apparently sometimes the brakes and lights are both grounded to the frame themselves and also grounded via a ground wire; for many trailer lights, they'd be grounded to the frame simply by being installed unless special care was taken to electrically isolate them. I had been under the impression that brakes were at times similarly grounded via their mounting to the axle, but it seems that was a false impression--they have wires for both sides of the coil to be connected up.