Can the Battery on a Trailer be Charged by Just a 7 Way on a Vehicle?

Updated 08/03/2021 | Published 08/02/2021

Products Featured in This Question

Adapter 4 Pole to 7 Pole Vehicle End Trailer Connector

(600)

$31.18

Redarc In-Vehicle BCDC Battery Charger - Dual Input - DC to DC - 12V/24V - 40 Amp

(87)

$620.00

Buyers Products 2-Way Die-Cast Zinc Trailer Connector - Truck Side - Horizontal Pin Arrangement

(32)

$12.90

Buyers Products 2-Way Die-Cast Zinc Trailer Connector - Trailer Side - Horizontal Pins with Spring

(33)

$13.90

Question:

I was surprised to read from Reno H that the 12v wire from a 7-way connector will not work to charge my trailer’s 12v marine battery, only maintain it. I always hear from others that their batteries charge up on a long drive. I guess they have spent $400 on a Redarc dc/dc charger? Also, I have a 400 watt AC outlet in the back of my Toyota TRD. I have tested it to prove it appears to charge my battery via an AC charger sitting in the truck bed with long cables running to the terminals. I’ve never done it on the road. Is this a dumb idea? Thanks for the help

asked by: Rob F

Expert Reply:

You are correct in that connecting a trailer battery to the 12 volt port on a 7 Way plug will not charge it and will only maintain the charge on said battery. Odds are the people that are actually charging their batteries do either have the Redarc # 331-BCDC1240D or something similar.

If your set up is working for you, I would stick with it. However, it may be a good idea to set it up a little differently. The Buyers Products 2-Way Die-Cast Zinc Trailer Connector - Truck Side # 337TC1002 and Trailer Side # 337TC2002 can be used to create something a little safer, just in case. This would act the same as your 7 way in the case of trailer separation, but will require some creativity to mount on your vehicle.

expert reply by: Lazer S