Which Terminal On a Trailer Connector is Used to Maintain a Charge on the Trailer Battery

Updated 11/23/2011 | Published 11/22/2011

Question:

What pin do I test for keeping battery charged from truck to trailer??

asked by: Steven P

Expert Reply:

If you have a 6-Way connector, the center pin is the 12 volt power and is usually the pin that would be used for charging a trailer battery.

If you have a 7-Way connector, the #4 terminal at the 1 oclock position is the 12 volt power terminal that would be used for charging. I am including a link to a FAQ page on wiring that will show the connectors and the functions of each terminal.

When your trailer battery is connected to either of these terminals it will allow you to maintain a charge on your trailer battery, it will not charge the battery from a discharged state.

You will want to make sure to unplug the trailer when the vehicle is not running to avoid discharging the battery on your truck, or you can install the Tow Ready Battery Isolation Solenoid, part # PK5231201. This solenoid will need to be installed in-line with the 12 volt power wire and a lead ran to a circuit that will only be hot when the ignition is turned on. This will keep the battery from pulling a charge unless the vehicles ignition is on.

expert reply by: Jeff D