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Roadmaster Battery Charge Line Kit for Towed Vehicles

Roadmaster Battery Charge Line Kit for Towed Vehicles

Item # RM-156-25
Our Price: $34.06
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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. Great prices 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 Satisfaction Score:

Customer Reviews

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

Average Customer Rating:  4.8 out of 5 stars   (473 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.


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

I have no regrets with this purchase. Items preform as advertised with no issues. I am very satisfied with Roadmaster and Demco products.
Jeffrey - 11/19/2022


Forgot this when I ordered my tow bar and parts. Arrived in just a few days. Easy install.
Suggestion for Roadmaster - need to provide terminal covers. Made my own using some vacuum hose caps and rubber tubing.


I purchased this Battery charge line kit in order to safeguard the battery on the tow car. Works perfect and you don't have to worry about your tow car battery even on extended trips across Canada. A very small investment to maintain the vehicle battery and always have full power when needed. Thank you very much etrailer.


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.


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


Excellent service. However, We been waiting for this part. First the Post office said that it would deliver on Sept 9, then Sept 10 and it was here Sept 12. We had to postpone our trip because of the delivery date. Do not sent mail trough the USPO they do not deliver on Saturday or Sunday.


Was on time as promised. Very helpful customer service representative and I would recommend them to anyone looking for trailer parts or towing parts.


My husband orders from etrailer all the time. He loves your products


My experience with etrailer was good from the perspective of the cooperation and pleasantness. However, even though I was clear on the tow bar I had (Blue Ox) and the vehicle I was towing (2005 Dodge Dakota) when the tow package came and the shop I had installing it got to the end of the installation, it was discovered that the wrong pins were sent, i.e. they wouldn't lock in place - too short . At first we couldn't determine what the problem was, so I called etrailer back. Was told those were the correct pins. Finally called Blue Ox directly and the rep immediately told me (after I gave him the PN) that those were the wrong pins. Without me asking he offered and did send two replacement pins free of charge. They worked perfectly.


product works great! Customer service was outstanding, new exactly what I needed for my RV/towing needs and easy to work with !


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.


Etrailer is fantastic, thank you Nicole!


Installation instructions were great


Yes I use it from my motorhome to the jeep I tow and to the trailers.


I called in and explained my problem and Victoria was quick to understand what was happening ( or not happening) and explained the productI would eliminate my problem. I received the kit in three days and installed it and I will be towing without having to worry about starting my vehicle at the end of a long day of towing .


Item arrived promptly. Quality was very good, and the installation instructions were easy to follow. Price was also very reasonable compared to other similar offerings.


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.


Easy installation


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.


Thumbs up! If there’s a problem the staff will do their best to make things right. The videos for install are the best and very helpful…Keep up the good work.


It works and was not too difficult to install in my 2008 Jeep Wrangler.


I’ve ordered several parts from etrailer all have been good quality and showed up quickly. The advice from the consultant are spot on. There videos for installation are very helpful also.


Does good job keeping car battery charged when towing.


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


Perfect application

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