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Roadmaster Battery Charge Line Kit for Towed Vehicles

Roadmaster Battery Charge Line Kit for Towed Vehicles

Item # RM-156-25
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Kit allows up to 15 amps from your RV's battery to be used to maintain the charge of your towed car's battery while the car is being towed. Charge line connects to the 6-way or 7-way plug on your vehicle. Requires separate charge line in RV. 1-800-940-8924 to order Roadmaster accessories and parts part number RM-156-25 or order online at Free expert support on all Roadmaster products. Guaranteed Lowest Price and Fastest Shipping for Roadmaster Battery Charge Line Kit for Towed Vehicles. Accessories and Parts reviews from real customers.
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Roadmaster Accessories and Parts - RM-156-25

  • Tow Bar Wiring
  • Battery Charge Line Kit
  • Roadmaster

Kit allows up to 15 amps from your RV's battery to be used to maintain the charge of your towed car's battery while the car is being towed. Charge line connects to the 6-way or 7-way plug on your vehicle. Requires separate charge line in RV.


  • Maintains the battery charge in your towed vehicle while the car is being towed
    • Provides just 15 amps to avoid overcharging
  • Connects battery to 6-way or 7-way plug at the front of your towed car
  • Receives power from your RV
    • Requires Roadmaster's motor home battery line (RM-156-75 - sold separately) if no charge line is present in your RV
  • Includes 14-guage wire, split wire loom, circuit breaker, and hardware
  • Made in the USA
  • Limited Lifetime Warranty

156-25 Roadmaster Battery Charge Line Kit for Towed Vehicles

Installation Details RM-156-25 Installation instructions

Video of Roadmaster Battery Charge Line Kit for Towed Vehicles

Videos are provided as a guide only. Refer to manufacturer installation instructions and specs for complete information.

Video Transcript for Roadmaster Battery Charge Line Kit Review

Ryan: Hey everybody, Ryan here at etrailer. Today, we're going to be taking a look at the Roadmaster battery charge line kit for towed vehicles. The charge line's going to be a really simple kit. It's just going to consist of a little bit of wiring and the breaker that we have mounted right here out of the way. On the purpose of the charge line kit is to more or less trickle charge or maintain your battery whenever you're flat towing it down the road. And that's important because your braking system is going to use your battery power to operate whenever you are towing it.

And the last thing you want is to get to your destination and unhook and go to start up your truck and the battery be dead. But the charge line, you're not going to have to worry about that. It's going to maintain that battery life, that way you're not going to have to deal with trying to get some jumper cables from your motor home to here, deal with grabbing a jump box or even bothering someone else to help you out.We do get some questions asking about if the charge line kit is going to affect your motor home's battery, which is definitely understandable, but the answer is no. Since the charge line is going to get the power from the auxiliary power source at the seven-way plug, you're not going to have to worry about it stealing or robbing your motor home's battery power. So the way it's going to get that power, the current is going to run through your cable from the back of your motor home into your plug and the charge line wire is going to be connected to the back of the plug.

From there, your wires is going to run up to one side of the breaker and the breakers there to prevent the current or electricity from backfeeding so that'll kind of put your mind at ease, knowing you're not going to have to worry about that power backfeeding. With that being said it'll cross the breaker, come through this wire, and this is going to run and get connected to the positive terminal on your Ranger's battery.So overall really simple component, that's going to keep our battery charged and one less thing we're going to have to worry about, and that can really make a big difference whenever you're on vacation, going from relaxing to stressful if your battery does die. A charge line kit is going to prevent that. And that'll finish up our look at the Roadmaster battery charge line kit for towed vehicles.

Customer Reviews

Roadmaster Battery Charge Line Kit for Towed Vehicles - RM-156-25

Average Customer Rating:  4.8 out of 5 stars   (327 Customer Reviews)

Kit allows up to 15 amps from your RV's battery to be used to maintain the charge of your towed car's battery while the car is being towed. Charge line connects to the 6-way or 7-way plug on your vehicle. Requires separate charge line in RV.


This is an easy install with simple instructions. Verify connection to vehicle 6-pin trailer power connector and correct stud (gold) on circuit breaker block; other stud (silver) goes to BATTERY.


have successfully completed the installation of the following items that I purchased from etrailer:

> Nighthawk RM-676 tow bar
> RM-524458-5 base plate
> DEMCO Stay in play DM86VR
> RM-152 diode wiring kit
> RM-156-25 charge wire kit
> RM-88400 brake switch relay kit

I work slow but methodically. I had no issues other than the high degree of difficulty for a 68 y/o man working alone. This project exceeds the abilities of someone NOT mechanically inclined. There is also the need for some specialty tools. I found that feeding the wiring through the dash, firewall, and underbody was more difficult than installing the front baseplate. Overall, I am satisfied with the function of this installation. I am glad I did it myself rather than having it done.

Tow vehicle: 2021 Entegra Emblem 36U
Towed vehicle: 2018 Ford Fusion Platinum Energi


It was a good experience. The only negative is not being able to see trailers in person, but I knew that going in, so that’s my decision. Overall the value was excellent, and I was able to get the trailer i wanted at a great price with plenty of custom upgrades at a far better price than anyone local, which is why I chose to buy a trailer from Half way across the country. I would certainly do it again.


I ordered all the parts required to safely flat tow out 2017 Jeep Cherokee Trailhawk from The only part they didn't have was the Mopar Flat Tow Enhancement kit Jeep requires to flat tow this model.

Ordering from them was great, the website is easy to use and I was able to locate all the pieces compatible with my specific vehicle. The expert recommendations help my decision choosing the right parts. I ordered from etrailer even though I found some of the parts on other websites a little cheaper. I chose to pay a little more because of all the effort etrailer has put into installation videos and guides. I was very pleasantly surprised to learn from etrailer that they have a price match guarantee!

So my equipment consisted of the following

Mopar Flat Tow Enhancement Kit (from Jeep)

Roadmaster Battery Charge Line Kit for Towed Vehicles

Mighty Cord 7-Way RV Style Trailer Connector - Trailer End

WesBarg 7-Way, RV-Style Connector w/ 6' Long Coiled Cable Trailer End

Pollak Black Plastic, 7-Pole, RV Blade-Style Trailer Socket - Vehicle End

Hopkins Custom Tail Light Wiring Kit for Towed Vehicles

SMI Stay-IN-Play DUO Supplemental Braking System

Roadmaster Brake-Lite Relay Kit for Towed Vehicles

Blue Ox Alpha Tow Bar - Motor Home Mount - 6,500 lbs

Blue Ox Base Plate Kit - Removable Arms

Blue Ox Tow Bar Cover - Aladdin, Aventa LX, Aventa II

The installation videos are great but not all inclusive. Take the time to read the instructions that come with the parts. This is a major project, I took about 30 hrs over a full week but as you'll see in the pictures I took s few extra steps to make a cleaner look.

Some of those extra steps:

The base plate install requires the bumper be modified cutting off a flange on each side, I spray painted this to prevent corrosion.

In the install video of the baseplate on the drivers side they use an extra quick link (not included) to run the safety cable around the wiper fluid reservoir. I took the time to remove it and run the safety cable behind it.

I didn't want our nice new vehicle to look like it can be towed so I played the brake away switch and 7 way trailer plug behind the license plate, so when not being towed our vehicle looks great!

Some things to be aware of. The Brake air cylinder that mounts to the brake pedal with four bolts may need longer bolts, it did on our Jeep. Spend the money for weather tight heat shrink crimp fittings. The Hopkins wire harness was about 1.5 feet short to get to my plug location. Buy extra zip ties, electrical tape and split loom.

I recommend reading all the various installation manuals and watching all the videos because the various components integrate together and if you install one at a time you'll be doing a bunch of extra work.

The brake light relay is a real pain in the butt, not because of the hardware but because of the location of the brake light switch which is very hard to get to.

Overall I am very happy with the products and how the installation looks. We haven't towed it yet but do not expect any problems.

Still very happy with our purchase. We’ve towed over 10k miles and have had zero issues with our tow setup. I’ve shared my experience with several other RVrs and recommended your company for their needs. Thank you,
Roy - 07/30/2018


These were exactly what I needed. I changed tow vehicles to a Honda HRV (manual) and the only base plate available was the Roadmaster. These adapters took about 10 minutes to change my Blue Ox tow bar to accept the Roadmaster.


Ordered and install base plate over a year ago and finally got to use it a couple of weeks ago because motorhome was in shop waiting on parts. Pandemic and supply chain issues. Anyway, the base plate and accessories work great. Dinghy tracks well. Hardly know it’s back there.


Over the past few years, I've ordered several items from etrailer. The purchasing process was very easy and timely. They're instructions and videos for installation are spot on! I will continue to buy from etrailer for my motorhome and towing needs


This is really a must for most toads if you have to have the key in the ignition and/or have a braking system. Easy to install.


Installed as per installation video and all went great.

towed over 7000km last year and worked great. no dead battery
Greg - 04/25/2022


I received the charge line on time and easy directions enabled me to do a self install!


This is exactly what was needed to charge the car while traveling down the road. Once the operator error was remedied, no problems or concerns

2013 Newmar Canyon Star
2018 Equinox


Easy install for anyone with good mechanical ability. Towed my Suburban 11,000 miles so far with no issues from the base plate.


Works great. Get this the same time you get your wiring kit. Nice to do the wiring on the 6 pin plug once. Installation videos are great.


Never disappointed with etrailers service

Great company to do business with.


was not needed (returned) because the Delta Force supplemental brake kit already provided


Installed on an F150, turned out I didn't need it, but oh well, it's there.
I would have preferred a diode rather than the circuit breaker, to prevent back-feeding the motorhome.


Had it installed by my RV Service guy, and it’s worked great for us in towing our Jeep Cherokee with the Roadmaster Falcon 2 towing system!


From a [social media] post I read yesterday... "I tow my 2021 Equinox behind the RV. Yesterday the battery went dead." Any question on why you need this? Didn't think so.


Product pretty straight forward and appears to be of good quality. Only reason for 4 stars is the directions from the Manufacturer could have been explained a little better. Not that complicated. trailer as usual great job of recommending product to solve problem,


Just what I needed to put a charge line on my cord Escape


The telephone support was excellent. I can't rate the product since it hasn't been installed yet.


The Roadmaster Battery Charge Line Kit was easy to install and exactly what I needed. thank you


Great price, easy ordering, and shipping arrived as promised Will order again from etrailer


Probably really need this,but it better to not worry about losing charge to braking system.


Kit works well. Suggest longer lenght of wire provided with battery under passenger seat

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