Charging Trailer Batteries From Tow Vehicle and AC Outlet

Updated 07/02/2018 | Published 06/28/2018

Products Featured in This Question

Pollak 9-Pole, Round Pin Trailer Connector - Trailer End

(52)

$17.57

10 Gauge Wire - Blue Primary - Per Foot

(107)

$1.65

CTEK MULTI US 7002 12-Volt Universal Battery Charger w/ Pulse Maintenance and Backup Power

(98)

$199.99

Question:

Have an enclosed carhauler trailer w/ 9 pin plug, breakaway brake system w/ battery and an interior 12v led light. Since the trailer sits unused and unhooked from a tow vehicle but plugged into 30 Amp powermost of the time, I would like to add a battery, battery charger and more led lighting. I read that the black colored wire from the tow vehicle provides 12 volt power and that is where the breakaway battery and interior light get their power. How would I set up the trailer to have both batteries get charged from the tow vehicle while underway and also both be charged by the battery charger when uncoupled?

asked by: Mike

Expert Reply:

In order to charge your trailer batteries from the 9-Way on your tow vehicle while in transit, you will just need to run 10 gauge wire like # 10-1-1 (sold by the foot) from the vehicle battery's positive terminal to the 12V power circuit of the 9-Way (if not already done). You will then run wiring from the 12V pin on the trailer 9-Way to your batteries. Keep in mind that this will provide a maintenance charge while towing but it won't be enough to charge up a dead battery. You are correct that the 12V wire is typically black, but it's always best to verify this on your particular vehicle as wire colors can vary.

For charging up the batteries completely with the trailer parked and uncoupled, you would need to use a separate wall charger like the CTEK # CTEK56353. I have attached a short video demonstration and the instructions manual for this charger that you can also take a look at.

expert reply by: Chris R