Connecting Deep Cycle 12V Battery to Vehicle Battery

Updated 08/11/2017 | Published 08/09/2017

Products Featured in This Question

Starter Solenoid - SPST - 12 Volt - 100 Amp - Continuous Duty - Grounded

(13)

$35.41

10 Gauge Wire - Blue Primary - Per Foot

(108)

$1.65

40 Amp In-Line Circuit Breaker - Perpendicular Mount Bracket

(97)

$9.85

Firestone Fuse Circuit Tap Kit

(40)

$22.03

Question:

Hello. I added 7-pin wiring to my 2002 Ford Ranger to tow my 13foot travel trailer with brakes. I have one more positive from my trucks battariy... can I directly wire my deep cycle 12vbattery in the trailer ?? Or do you recommend a switch/fuse in-between??

asked by: Woody M

Expert Reply:

To wire your vehicle battery to your deep cycle trailer battery, I recommend using a 40 amp In-Line Circuit Breaker, such as # 9510, along with # 10-1-1 to wire your trailer connection. I also recommend the Battery Isolation Solenoid # PK5231201, which will allow the trailer to draw power only when the vehicle is running. Otherwise your trailer battery could drain the battery in the tow vehicle when the vehicle is turned off.

You will also need to use an ignition-controlled circuit in your truck to activate the solenoid. You will need a fuse tap to access the switching function on this circuit, such as part # F2526 from Firestone. This plugs into the fuse socket for your radio and connects to the center post on the solenoid. 12V power from the tow vehicle battery connects to either the left or right solenoid terminal, and the power output exits the other side.

I've attached an installation video showing how to connect the Firestone part to your vehicle. I've also included an image identifying the solenoid hookup points as well as a review video of the solenoid.

expert reply by: Amber S