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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. 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 Installation - 2022 Chevrolet Equinox

Hey everybody. Ryan here at etrailer. Today, on our 2022 Chevy Equinox, we're gonna be showing you how to install the Roadmaster battery charge line kit for towed vehicles. But before we do that, why don't we check this out and kind of go over why it's a good idea to use one of these. When it comes to setting up a flat tow, oftentimes, there's a handful of small components that are often kind of overlooked or forgotten about that you can use to make everything more complete, make your life a little bit easier, and have things set up the right way. And a battery charge line kit is one of those components.

And matter of fact, this is something that I don't only recommend for the Equinox, but just about every flat tow that I do, I always recommend one. And what this is gonna do is essentially trickle charge or maintain your vehicle's battery whenever you're flat towing it. And a lot of times, you can run your battery low because the vehicle's supplemental breaking system uses the battery power. And so, what can happen is, you know, you're over the road, six, eight, 10 plus hours. Over time, constantly just stealing a little bit of juice from the battery, it can wear this down and make it flat.

And so, you'll get to where you're going, try to disconnect, try to start the car, and it's dead, and then it's a big pain. You gotta deal with charging it, getting the jump box and your cables out, and everything else. So, having this charge line is gonna prevent all that. It's gonna keep your battery topped off and ready to use whenever you go to start the vehicle. Not to mention too, on newer cars nowadays, a lot of things are electronically controlled.

A lot of times, you'll have electric assist steering, electric assist brakes, and everything's computer controlled in a sense. And so, maintaining proper voltage is essential for a lot of those things to work. And with a dead battery, obviously, that's not gonna happen. So, a charge line will keep all that stuff kind of go into, I'm not sure if the Equinox uses all that type of stuff but just generally speaking. And another thing that this can help prevent is premature failure of your battery.

So, a battery will have so many cycles it can go through. So, if you drain this thing down and then fill it up, and drain it down and fill it up, drain it down, fill it up, that's going to decrease the overall life expectancy of it. So essentially, trickle charging this and keeping it topped off the whole time should really extend the life of the battery and keep it in good working condition. The way the kit is gonna work is really simple. It's gonna use some of your motorhome's auxiliary power coming out of the seven-way. That current's gonna flow up through here through a breaker. And this is just a circuit breaker. It's gonna protect everything in case there's a short or something along them lines. And then that current's gonna flow through the wire to your positive battery terminal. Now, you are going to have to have your car battery needs to be in good working condition. This isn't going to bring your battery back to life if it's already dead, or has a bad cell, or something along them lines. And it's not going to affect your motorhome's batteries either because your motorhome has its own charging system. It uses an alternator and there's extra amperage that is sent back to the seven-way that we can use. So, it's not gonna harm anything there or create any issues as far as that goes. Other than that though, at the end of the day, a small but really important component. This could really save you a lot of hassle in the long run. As far as getting it installed, it's really not bad. Essentially, it's two wires and really shouldn't run into too many issues. So, as long as you take the time, it really shouldn't give you any trouble. But speaking of that, why don't we go ahead and hook this stuff together now. To begin the installation for our charge line, we're gonna be here at the front of our vehicle. And clearly, we have the front fascia taken apart. That's because we're doing all this at the same time that we installed our base plate, which is what I recommend doing. We have all this extra room to work. I also suggest doing this the same time that you're doing your diode wiring because this is gonna route in a similar matter, a similar way. And you'll already be in the back of the connector plug here, so just save you a little bit of time. But with that said, you wanna take your charge line wire here, the red wire. Bring it down to where our connector plug is. You'll strip back the insulation a little bit. Something like that. Give those wires a good twist. And we're gonna hook this up to the center post on the back of our six-way connector. So, you just back out that set screw a little bit. Take the wire and carefully place it into the terminal there and then just tighten the set screw back down. Now, that we're hooked up, we can take our rubber boot, put it back over our six-way connector. And you can apply dielectric grease, and sealer, and stuff to the terminals inside there, and tape everything up and keep moisture out. I like to wait till the very end of a flat tow setup though to do that just so we can make sure everything's working and stuff. That way, If it's not, it's not a big mess in here. But for now, we'll go ahead and just mount this up to our base plate. And then the wiring is gonna get routed inside of the engine compartment. So, just ran it along through here and up where it comes in. Essentially, right underneath our headlight. So, here's where our charger and wire comes up in engine compartment. And this is gonna get routed to our breaker, which I have mounted right here. So, I just remove this nut using a 10 millimeter socket, put this over it, and tighten it down. So, these screws, or the nuts rather, on the breaker, go ahead and take those off. Careful with these. They're easy to drop and hard to find. So, we'll get them off. Then we're gonna take our wire and cut it to length. So, we'll go about right here. Cut that. Strip back the insulation. Take a small ring terminal then crimp that on. And then this is gonna go over the gold post. It's gonna be labeled battery, so you might be tempted to hook this up the other way, but since the motorhome is essentially acting as our battery, this is how we do it. We'll reinstall the nut. Come back with the a 3/8 socket and then snug it down. Then for our other wire here, we're gonna strip back both ends. One end we're gonna crimp on a small ring terminal and the other end is going to receive a large ring terminal. Get them connected. The small end will go over the silver post there. Get that tightened down. Once that's snug, this is gonna go over to our positive battery terminal. So, we should be able to pry this up. Let's see if I can get this whole piece off. Make it a little easier. And we will be connecting this to the positive terminal there. I'll take this off using a 10 millimeter. And a lot of times, these aren't designed to come completely off, at least very easily. And if that's the case, not a big deal. We have a way around it. Loosen this up and this is one of those. So, I'll show you what we're gonna do here. We'll loosen this up quite a bit. About like that. And then we'll take our ring terminal and you're gonna cut a small opening in it. And then with this being a little bigger, what I like to do is kind of pinch the ends closed again and then recut it out. It just kind of gets a better bite around it, I feel like. And we're just gonna slide this in like that. And then I'll just tighten the nut back down. Once this is tight, that's really all there is to it. And that'll finish up our look at and our installation of the Roadmaster battery charge line kit for towed vehicles on our 2022 Chevrolet Equinox..

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   (747 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.


I purchased this as part of a package which included; Hitch and wiring for my 2022 Equinox, Base plate, Tow Bar, brake System and connecting air hose, break away cables, LED tow lights with wiring harness, and a trickle charger to keep the Equinox battery from going dead while I was towing it behind my class A RV.
I had etrailer do the install of all the components on my car and RV. All the workmanship was excellent and done in the amount of time they said it would take. Also because they did not have a video of this equipment being put on this year and model vehicle, I gave them permission to make a video(which added a extra day and a half to the install)and the installation was free. Everything has worked perfectly and I couldn't be happier. Etrailer is my go to for anything towing and also RV parts.


The Roadmaster battery charge line kit for our Honda CRV was delivered as advertised. It was fairly easy to install, and has worked well for us. We get asked what the receptacle mounted under our front bumper is for, as it is exposed, but understandable.


A necessary addition to assure the towed vehicle battery isn't discharged by the brake assist system. Very complete kit and easy to install.


Clean install by eTrailer. To me it's a set it and forget it. My Ford Maverick has not had any electrical problems after towing. The Charge Line Kit must be doing its job.


Installed easily. Works well, no more problems with hybrid battery discharging under tow.


The Roadmaster brake connection kit has worked flawlessly on our toad. Thanks!


Definitely needed for flat towing to keep battery charged on tow vehicle. Simple install.


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,


Alex was very helpful in finding a solution to outfitting my new toad with the equipment I had onhand


This was a pretty easy install after we completed the receiver plug install. We installed on a Jeep JK and there were plenty of places to safely route the wire to the battery area. Instructions and video were very helpful.


This was exactly what i needed to keep the battery on my towed vehicle charged. Came with everything needed to install.


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



Everything is working great! No problems using this product!

Etrailer Expert

Mike L.


@John That's awesome!


Simple installation. I installed it while installing the Roadmaster direct-connect baseplate and smart diode lighting kit. Best to install before reinstalling your bumper cover on a 2023 Equinox LT (AWD).


Worked like a charm. Good instructions and video guidance!


Easy installation


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.


Solid and reliable cord. Mounting the connectors was straight forward and not difficult.


Need to add about 24 more inches to the red wire.



The terminals should really have a cover. Even mounted away from other items, they are hot and someone will accidentally hit them with a wrench causing electrical damage, not to mention sparks and burns. I’m made my own with a piece of foam rubber.

Etrailer Expert

Mike L.


@Randy That's a great idea, thanks for sharing that! A product such as the # SWC50122 liquid electrical tape could also be used on the ends of the terminals to protect them...


This works as advertised but it could be improved by supplying a self-resetting relay with the rubber cover so the 12v terminals are insulated rather than exposed.


Keep battery on tow vehicle charged


This kit worked out great for my 2022 Chevy Equinox. I like how it has separate side plates, which make it easier to attach the main bar. The points where it attaches to the frame seem plenty secure. It is important to watch the videos provided by etrailer as Ryan is very thorough and has good tips for installing. I would also recommend installing additional wiring while having the front end off. Overall, I was able to complete in my driveway. The hardest part was sorting out the wiring for whatever braking and tail lights you decide on. William S helped me pick all the necessary components needed for flat towing behind my Jayco RV. I am looking forward to a summer of camping and having more freedom to explore the area, now having a car.


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 .

Terry T.


The product I received was not used. The wire size was thread thin. I have not wired the Car battery to the MH power source. I will use the a fuse holder with 14 gauge wire. The tow package I purchased in 2019 has worked well and I am very satisfied with what I received. I would suggest you up grade the wire size in your MH to towed vehicle battery supply. I did purchase 25 foot ott 1 booster cables which should be something A &amp C class motor homes should have regardless.


eTrailer was very helpful in choosing the correct hitch for our rv and car. They also provided a special brake application in the car that makes it super easy for toad braking.
I am 72, and I hook up this toad and pull it with confidence. The instructions to hook up the toad was presented with ease. They knew exactly what they were doing, and we didn't rush through the demonstration. I would recommend eTrailer to anyone.


I attempted to order directly from Blue Ox and it was going to be 6-8 weeks for delivery, Went to etrailer and it was at my door within 48 hours! Impressed!

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