How to Prevent Breakaway Battery From Draining Winch Battery Power

Question:

I want to use this Battery Isolation Solenoid # PK5231201 but I would like to see a wiring diagram to hook it up to my 7 pin junction box. I have the battery on my trailer to power my winch but once I connect if to the auxiliar power my breakaway switch battery stays charging all the time. I would like to be able to have my winch battery hooked up to my junction box that way it can charge while my trailer is hooked up to my vehicle. Any help would be greatly appreciated.

asked by: Gabriel G

Expert Reply:

If I'm understanding you correctly the starter solenoid # PK5231201 is not the solution to your problem. Based on what you have described, it sounds like both the breakaway battery and winch battery are hooked to the 12V power coming from your 7-way. This is what I would expect to see, and would allow for a maintenance charge on both when hooked up to the tow vehicle. However, with the winch battery and breakaway battery on the same circuit you see the breakaway battery constantly charging when the tow vehicle is disconnected.

Assuming that is correct, the problem is that the breakaway battery is charging off of your winch battery when you're not connected to the tow vehicle. The solution is to install a diode # RM-790 between the breakaway battery and the winch battery. This will allow power to run to both batteries from your 7-way to keep them maintained, but prevent power from transferring back to the breakaway battery when the 7-way is disconnected.

It is also worth noting that the power from your tow vehicle doesn't actually charge the batteries on your trailer. It is only designed to maintain the charge on those batteries. To actually charge the battery you need a charger like the # NOC54FR.

expert reply by: Robin H