How to Prevent Trailer Battery From Backfeeding to Vehicle Battery

Updated 04/01/2019 | Published 03/29/2019

Question:

If I connect the trailer battery to my 7 way plug would it backfeed from the trailer to the vehicle if the vehicle isnt running and the trailer battery has a higher voltage?

asked by: Eric

Expert Reply:

While unlikely, it is certainly possible that the trailer battery could backfeed to your vehicle's battery when hooked up under the scenario you described. To make sure this doesn't happen all you need to do is add a single diode like the Roadmaster # RM-690.

This will install between the trailer battery and 7-Way and will only allow power to travel in one direction (to the trailer battery). This particular diode is rated at 85 amps.

expert reply by: Chris R