Is a Battery Isolator Needed When Using 7-Way Connector To Charge the Trailer Battery

Published 06/25/2010

Question:

I have a 2008 chevy silverado with a tow package. I have the accesory power and brake controler hooked/set up for my 7 way trailer plug. I would like to use the accesory power feed to charge my winch battery on my trailer. Is it neccesary to have an isolator or another device Im not aware of? If I dont need an isolator, would I just connect the accesory power to the positive on the battery, and then ground the negative to the trailer?

asked by: Blaine

Expert Reply:

You will need a battery isolator, like Battery Isolation Solenoid, part # PK5231201, if you plan on leaving the trailer connected to the truck when the truck is off. If you unplug the 7-Way, the trailer battery cannot drain the truck battery. If you leave them connected, you would need an isolator to keep the trailer from drawing down the truck battery. The isolation solenoid has three connections.

If you are looking at the unit with the dome facing up and the 12v sticker right side up (like we have it shown in the picture on the product page), the left terminal is input, the right terminal is output, and the middle is auxiliary which will be connected to a source that will act as a switch to engage/disengage the solenoid. He stated that normally, the middle terminal is attached to an ignition switch wire.

If you do not mind unplugging the trailer from the truck, you would wire the battery as you suggested. It will not charge the battery from dead, but it will maintain a good, charged battery.

expert reply by: Patrick B