Can a Trailer-Mounted Auxiliary Battery be Overcharged by 12V Feed on Vehicle 7-Way

Question:

I have a 2010 GMC Sierra and it has the tow package with the 7 pin connector. I want to put a battery in my enclosed cargo trailer to power interior lights when its not connected to or plugged in the toe vehicle. What do I need to do for this? Then my next concern is can the trailer battery be overcharged on long road trips?

asked by: Bret

Helpful Expert Reply:

If you install an auxiliary 12V battery in your enclosed trailer to power its lights you can use the Battery Isolation Solenoid # PK5231201 to prevent the trailer battery from draining the tow vehicle battery while connected. The center post on the solenoid (see the linked photo please)receives an ignition-key-controlled signal from the vehicle (from any circuit that is controlled by the key - such as a power antenna) and this tells the solenoid to let 12V current pass from the vehicle to the trailer battery.

If you prefer you can instead disconnect your trailer's plug from the tow vehicle socket whenever the vehicle is off; this too will prevent accidental draining of the vehicle battery. Using the solenoid along with a fuse tap # F2526 means you don't have to remember to unplug the trailer.

The 12V feed from your 7-way carries enough current to maintain a battery but does not have enough to charge a depleted battery. You do NOT need to worry about overcharging the trailer battery since it gets only a trickle-type charge.

Before each trip you should charge your trailer battery with a charger like the CTEK MULTI US 7002 12-Volt Universal Battery Charger # CTEK56353. You can also use it to top off your vehicle battery as well.

expert reply by: Adam R