How To Charge Vehicle Battery Using Trailer Battery While Hooked Up To Shore Power

Published 01/28/2020

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Question:

I have a camper that I leave plugged into shore power and it has solar panels which keeps the camper batteries charged. I want to run wire from the camper batteries to the truck batteries to keep them charged also. Do I need a diode on both positive and negative wires. Also is there a voltage in these diodes.

asked by: Andy N

Expert Reply:

The purpose of a diode is to stop the back flow of electricity. I can honestly say I have never heard of someone wanting to run a charge line from the trailer battery to the vehicle battery but I'm sure it would be possible. That said, when you attach two batteries to one another via a charge line they will try to balance each other. Therefore, if the start battery has more juice than the trailer battery the trailer battery will pull from the start battery and vice versa. The diode however would prevent one battery from pulling so you could use part # RM-690 to make sure the trailer battery feeds the truck battery and not the other way around. There would only be one diode needed on the power wire. I diodes are rated for 12 volt DC current only.

That said, I really think a much better solution for you would be to just use a separate charger for the vehicle like the 2.5-Watt Solar Battery Charger part # PTW2997 or NOCO Genius On-Board Battery Charger part # 329-GENIUS5.

expert reply by: Conner L