Breakaway Switch Wiring

Please educate me. I'm working on refurbishing this trailer and part of that involves a new trailer electrical plug and distribution box, breakaway switch and battery box on the trailer. The distribution box has studs for ground, 12v hot, backup/auxiliary, left turn, marker, right turn, and trailer brakes.

There are two wires coming off of the breakaway switch. One wire goes directly to the trailer brake wire in the distribution box. The other goes to the positive side of the battery. The negative side of the battery goes to the ground wire in the distribution box.

My question is about hooking a wire from the 12v hot in the distribution box to the positive side of the battery. There is power here when the key is on. This should charge the battery on the trailer whenever it is hooked to the truck. My question is will this cause the trailer battery to overcharge or will the voltage regulator/alternator on the truck prevent overcharging?

Looking online, some trailer batteries/breakaway switches come with chargers built in and some do not. This one does not have one built in.

Pick up a solar charger,cheap and low powered enough that they won't overcharge the battery.

Hey! it looks like one of the white wires could ground to the terminal next to it!

I am thinking that you won't have anything to worry about if your truck is wired such that it can charge the breakaway battery. You might consider putting a 20a circuit breaker in the circuit between the breakaway battery and the 12v from the truck. The circuit breaker will protect the truck when/if the breakaway battery goes bad. You use a circuit breaker because it will close again when it cools off.

We had to put circuit breakers between the chassis wiring and the battery in the dump trailers we used to sell. The dump trailer battery would get weak, then the fuse between the truck and the trailer would blow. after it blew there was no chance that the truck could recharge the dump trailer battery. The dump trailers used the same battery for the breakaway brakes.

Not sure about your question, but why are the wires hooked up with the color of the wires not matching?? From the bottom, green to brown, 2 browns to green, yellow to red, where's the red wire go?? I HATE trailer wiring!!

Connecting it to the truck battery/charging system will not overcharge the battery.

That's the way it is designed to work.

Some have a diode in the circuit that prevents the trailer battery from being discharged should the trailer be left connected, and the truck battery became discharged.

The trailer had a 6 pin plug, and the box was broken so I bought a new plug wired to a new box. I reused the wires from the box back and the colors don't match. The picture is simply a test to see what wire goes where on the trailer.

(quoted from post at 22:24:30 01/31/22) Not sure about your question, but why are the wires hooked up with the color of the wires not matching?? From the bottom, green to brown, 2 browns to green, yellow to red, where's the red wire go?? I HATE trailer wiring!!

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The color difference is the difference between RV and Traditional wiring colors for 7flat blade connectors. Most of the pre-wired cords and boxes I've encountered have the wire Colors for the RV wiring. The blade positions in the plug and socket are the same in both cases, but you end up mixing colors in the junction box to keep the function correct for the blade in the connector. The picture shows the wire colors commonly used in each.

Ok, Now I understand. It would be much easier if there were 2 people when doing this. I usually end up by myself, did I mention that I HATE trailer wiring?

(quoted from post at 07:53:30 02/01/22) Ok, Now I understand. It would be much easier if there were 2 people when doing this. I usually end up by myself, did I mention that I HATE trailer wiring?

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Having several trailers and often ending up helping on others I bought a 7-way flat blade plug and socket. I made them up with 18" wires (colored to match the Traditional wiring) and put a label with the function on each wire, so the wire colors really don't matter. These test connectors make it easier to wire and trouble shoot alone. Wiring or checking a trailer, I plug the trailer cord into the test socket. Hook the ground wire of the socket to a battery (vehicle not required) negative post with a jumper and use another jumper (with a 20-amp fuse in it) from the positive post to the function I want to check the light on. And that function will have power on it if I need to find a bad wire in that circuit. The plug works to check that the vehicle socket is wired, and functions are working correctly. Using the ground wire out of the plug while testing the vehicle functions, confirms the ground to the vehicle is intact.

You can buy ready-made test plugs but having leads allows doing other checks. Using a separate battery eliminates running the vehicle battery down, unless it is kept running. Labelling the leads eliminates having to look back at what function a certain color wire is supposed to be. It cost a few bucks and some time, but I figure I had my money back in the time saving on the first truck and trailer's wiring I straightened out. I also have them for 7 round pin connectors. They do make test boxes to do this as well, but they cost even more. YMMV, works for me.

yes, I did something similar to this.

You are right, a helper can make a huge difference. Unfortunately, I've largely had to learn to work alone. Have to get creative at times...