Recommended Charger And Wiring To Charge Trailer Battery With Towing Vehicle Battery

Updated 06/21/2017 | Published 06/20/2017

Question:

I plan to tow a 13foot Scamp with a 2007 GMC Duramax 2500 HD and have a question regarding how to isolate my truck batteries from the trailer battery. I also want my truck alternator to efficiently charge the trailer battery when the truck is running. Ive read Adam Rs suggestion to use an isolation solenoid TR118665 from TowReady and understand his advice about wiring. In my truck, one of the pins on the trailer connector is always liveinch so I could install the isolator on that hotinch line to project my truck batteries from discharging. I assume that hotinch line charges my trailer battery when the truck is running but Im concerned that it would only provide a trickle charge since the wire size is small. I plan to use my trailer in remote areas without access to shore power and therefore would rely on my truck alternator to charge my trailer battery. For that type of use, should I run a separate heavy gauge wire e.g., 6 AWG from my truck battery through an isloator to the trailer battery via a plug that is separate from my 7 pin connector? If so, can you recommend the size of wire I should buy to run about 25foot and a plug that could handle that wire size? Finally, if I run a separate wire to charge the trailer battery through an isolator, I assume that Id also need to connect the hotinch line on my 7 pin connector to the isolator as well. Would that work, or do I need another isolator for each wire that is always liveinch going to the trailer? Thanks,

asked by: Richard

Expert Reply:

There is a way to charge the battery on your trailer with your vehicle. This is done by using the Redarc In-Vehicle BCDC Battery Charger # 331-BCDC1225D. This can be attached to the alternator on your vehicle and if you have the proper gauge wire, will provide a charge for the trailer battery.

I also recommend using 2 AWG wire, which will be sufficient for charging the battery over a long distance. This wiring kit has 25 ft of wiring capable of handling the power you need to charge the trailer battery.

I have attached a drawing that shows how the wiring is done using this charger.

expert reply by: Jeffrey L