How to Tell If Your Breakaway Switch Is Powered By Trailer Battery or Auxiliary Battery

Updated 03/12/2019 | Published 03/09/2019

Question:

Is my breakaway brake switch powered off my trailer batteries or should I look for an auxiliary battery

asked by: Ralph H

Expert Reply:

If you already have a breakaway switch and trying to find its power source, It is possible that someone could have wired the breakaway switch directly to the main battery on the trailer but it does not come like that from the factory. The breakaway switch should be wired to a separate battery. Most Breakaway switches come with their own battery and some come with a battery charger. The breakaway box is essentially a plastic box with a battery in it that powers the breakaway switch.

When a breakaway kit does not include a charger, the breakaway box has 2 wires. There is a wire to the breakaway switch and then splices into the trailer brake wiring. The second wire is the ground. The battery inside the breakaway box still needs to be periodically removed and charged or you can add a battery charger part # 20011. The black wire from the charger connects to the vehicle's battery to charge the breakaway battery.

The best option is to use a breakaway kit that includes a charging wire such as part # 20400. The Hopkins Breakaway kit with built-in charger has 3 wires and one of them splices into the 12V wire of the trailer connector to charge the breakaway battery while the trailer is connected to the towed vehicle. It also has a push-to-test button that shows you if the battery is getting low. The 12V wire does not over-charge the battery because the breakaway battery is designed with an automatic shut off feature once the battery is fully charged. I have attached a diagram that may be helpful.

expert reply by: Heather A