Charging a Trailer Battery from the Tow Vehicle Battery

Published 08/11/2017

Products Featured in This Question

10 Gauge Wire - Blue Primary - Per Foot

(108)

$1.65

40 Amp In-Line Circuit Breaker - Perpendicular Mount Bracket

(98)

$9.88

Starter Solenoid - SPST - 12 Volt - 100 Amp - Continuous Duty - Grounded

(14)

$35.41

Question:

How can I charge my RV battery from the towing vehicle my car or truck. I have a 7 pin connector so I can get 12 volts there, Do I need a charge controller.

asked by: Dan

Expert Reply:

There is no need for a charger or controller to give a maintenance charge to your trailer battery while towing it. You simply need to use 10 gauge wire # 10-1-1 along with a 40 amp circuit breaker # 9510 in-line.

So you will run a short wire from the vehicle battery to the circuit breaker and then a long wire from the circuit breaker to the 12V power at your vehicle side 7-way. Your trailer side plug will then have a wire that will run to the positive terminal of the trailer battery and a short wire from the negative terminal to the trailer frame. This will give you the maintenance charge whenever the trailer is connected to the vehicle. If you want to make sure that your vehicle battery only charges the trailer battery when the vehicle is running, you can add a solenoid like # PK5231201 which will have the accessory in the middle to attach to your ignition.

expert reply by: Jason S