Battery Isolation Solenoid to Protect Vehicle Battery from Discharge from Trailer

Question:

Hi, I currently have a car trailer powered by a 7 pin connector to the tow vehicle. It has a junction box and break away kit. Im adding a 12v battery to operate a winch. I would also like this battery to 1be charged off the tow vehicle and 2 operate the interior lights when the tow vehicle is disconnected from the 7 pin. Do you have a wiring diagram for this? Should I also add a solenoid to prevent discharge of the battery when the tow vehicle is turned off, and if so, is there a wiring diagram for this too? Thanks.

asked by: Matthew C

Expert Reply:

You can easily run a 12V charge line to the battery that will power the winch on your trailer.

Your existing 7-way setup includes a 12V circuit that also charges your breakaway battery. Inside the junction box you will make an additional 10-gauge wire connection at the post for the 12V auxiliary circuit and run this to the positive post of the winch battery. You can use bulk wire # 10-1-1 and ring terminals # 44-5310A. Your 12V feed should already have a fuse/breaker on it.

To protect the vehicle's battery from being discharged by power draw from the trailer when the vehicle is not running you can install an isolation solenoid on the vehicle, part # PK5231201. Simply connect one of the side terminals to your battery positive post and the other to wire leading to your 7-way. Then use a fuse tap # F2526 on any key-controlled circuit in the vehicle (such as a power antenna) to connect to the center tap on the solenoid. This will allow that key-controlled circuit to connect the 12V power feed only when the vehicle is running.

expert reply by: Adam R