Is Trailer Battery Being Able to Backfeed to Truck Battery a Problem

Question:

I’m wiring in a winch to my gooseneck. Wired my winch to battery, from battery to 7 gang box under trailer to maintain battery while truck is hooked up but naturally I’m now getting 12.5 volts dc at end of my plug. That won’t back feed into my truck and cause problems?

asked by: Daikin

Expert Reply:

In order for your truck battery to be able to charge your trailer battery it will have to have a connection to it that is going to have voltage like you tested. What you have is normal and the only possible downside would be if your trailer battery is basically dead and your truck battery ends up draining itself (if left connected for a long time) trying to charge it. When two batteries are connected they will seek to equalize the voltage between them.

Some truck 12 volt accessory circuits are active only when the vehicle is on and others all the time. If yours is all the time you can wire in a isolation solenoid part # PK5231201 which will only allow it to function when your key is on.

expert reply by: Jameson C