In this video, I install an inexpensive 12VDC wireless switch to turn my Renogy 40 amp DC-DC charger on and off remotely. This will be a nice option to have when towing the trailer. In hot weather, stop-and-go traffic, or while pulling a long steep hill, I may rather have the DC-DC charger off to keep the alternator from overheating. I won’t have to stop and manually switch it off.
I used the incoming alternator voltage from the truck to power the eMylo 12V switch. It then remote switches the 12VDC trigger power line to the DC-DC charger I had previously wired from my trailer marker light circuit. I elected to use the trailer running lights power so I won’t forget to turn off the charger when the truck is off, and we are parked.