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Does the Power Wire for a Brake Controller Need to Be Ran Directly to the Battery


Hi guys, First of all, thank you for all the helpful information provided. Your customer service is awesome. Now for the questions First a little background: I have a Little guy [email protected] tear that I tow with a 2017 Subaru Outback. Last year I installed a 7 way tow connector on the car and ran 10 gauge wire from the connector in back of the car to the battery positive terminal to charge the trailer battery. BTW I routed the wire inside the car because I thought it would be easier that way. That installation works fine and battery charges well so that is not an issue I think unless you tell me otherwise . At that time, I did not run a wire from the blue on the connector for the brake controller, since I was not planning to add electric brakes to the trailer. A close call during a stop last year changed my mind, so I just bough brakes, and drums and controller from you guys. Now for the questions. 1. Since I already have a 10 gauge hot wire very near where I will be installing the controller, could I tap into that hot wire for the controller? That way I would only have to run one wire from the controller to the battery negative and one wire from the controller to the brakes. 2. Since I am only running two brakes one axle do you think I could I get away with 12 gauge instead of 10 gauge from the trailer junction box to the brakes, and from the 7 pin harness to the controller. Thank you for your time, I look forward to your response so that I can get started with this project.


Expert Reply:

To answer your first question, it is possible to splice the brake controller's 12 volt power wire into the 12 volt power wire you have attached to the vehicle's battery to charge the trailer's battery but this is certainly not recommend. If I were you, I would just run the 12 volt power wire from the brake controller directly to the battery with the recommended circuit breaker for that particular controller placed 6" for the positive terminal. The problem that you are going to run into if you splice into the charge line is amperage draw in relation to the circuit breaker and also warranty. If the circuit breaker fails and the brake controller is damaged, the manufacturer of the brake controller would not warranty the product if you spliced into the charge line to power it.

To answer your second question, the recommended wire gauge for electric trailer brakes both from the braking assemblies to the junction box and from the 7-way to the controller is a 10 gauge wire. I do not recommend using a 12 gauge wire as it will not be rated properly for the amperage draw associated with the trailer brakes over the distance of the wire.

If you need the 10 gauge wire to connect the trailer brakes to the junction box then you can use part # 10-2-1 (per foot). The rest of the 10 gauge wire you will need for the brake output signal is part # 10-1-1 (per foot). If you also need a circuit breaker for the brake controller then you can use part # 9506P for 20 amp, part # 38630 for 30 amp, and part # 9510 for 40 amp.

expert reply by:
Conner L

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