Recommended Wire Gauge and Related Parts to Install 12V Battery Charge Line on 7-Way

Updated 11/21/2017 | Published 11/20/2017

Products Featured in This Question

Roadmaster Battery Charge Line Kit for Towed Vehicles

(1447)

$52.55

10 Gauge Wire - Blue Primary - Per Foot

(109)

$1.84

Ring Terminal - 12-10 Gauge Wire - 3/16" Ring ID

(72)

$1.36

Wire Loom 1/4" Diameter, 10' Long

(312)

$9.55

Pollak Circuit Breaker - Cycling/Automatic Reset - 40 Amp - Straight Mount Bracket

(50)

$8.05

Liquid Electrical Tape

(11)

$28.04

Question:

I want to install a circuit from my RV to charge/maintain my towed vehicle battery, but unfortunately, the 7 pin connector on my RV is not currently connected to a 12v hot connection. So I need to run a wire from my 7-pin connector to a 12V source on the RV. 1. I think my 7-6 pin cable is 16 AWG Im trying to verify. If so, is this OK to use to maintain a charge on the towed vehicle? what size fuse should I use? What steps do I need to take to prevent overloading the circuit and blowing the fuse? 2. If my existing 6-7 pin cable is in fact 16 AWG, should the charge wire on the RV and towed vehicle be the same? 3. Should the charge wire on the wire on the RV be connected to a switched source or an always-hot source, such as directly to the batter? Thanks.

asked by: Myron W

Expert Reply:

We recommend at minimum a 14-gauge wire for providing 12V charging power to a towed vehicle's battery, such as that included in the Roadmaster Battery Charge Line Kit for Towed Vehicles, item # RM-156-25. Naturally, a heavier-gauge wire would do better since it can deliver more current.

If you prefer you can use 10-gauge wire # 10-1-1, a 40-amp auto-reset breaker like # PK54540, ring terminals # 44-5310A and wire loom # 7509-10 to make your own kit.

You can avoid tripping the breaker (but don't worry - it resets by itself) by making sure your wiring connections are fee of stray wire strands and that the connections are protected with electrical tape or a product like # SWC50122.