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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.
Features:
California residents: click here
Videos are provided as a guide only. Refer to manufacturer installation instructions and specs for complete information.
Hi everyone, Jesse here with etrailer. Today we'll be taking a look at, and I'll show you how to install, the Roadmaster Battery Charge Line kit for towed vehicles on our 2020 Lincoln Navigator. The battery charge line kit is something we almost always recommend whenever you're setting up your vehicle to be flat towed. The process, as far as installation, it's pretty simple, especially if you are doing your other flat tow components at the same time. And what it does is, it will send a trickle charge from the motor home to the battery and the towed vehicle. And what that means is you won't have to jumpstart your vehicle at the campsite and you also won't have to stop every once in a while on your longer road trips and start up your towed vehicle to get that battery to charge up.
All that's gonna come in your kit essentially is a long piece of wire and a circuit breaker. That circuit breaker is just there to protect all of your other wiring from any back feeds or anything like that. Although this is a pretty simple piece of the flat tow puzzle, there is a lot of other components that you'll need to kind of wrap your head around. So, I'd understand if you have any questions, reach out to us. We'd be happy to get you pointed in the right direction.
When it comes to the installation with this charge line, as I've said before, it's a pretty simple process. However, you're most likely installing other flat tow components at the same time, so I'd understand if you're not looking to do that yourself. Check out our dealer locator. You can find someone local to you that would be happy to get you set up. If you are looking to see how this gets installed then follow along, and I'll walk you through the process.
Begin our installation by getting our wire into our six pole, so just strip back the end of it and this is gonna tie into our center post. So, we'll take a Phillips head screwdriver, back that screw off and slide our wire in place and get that screw tightened back down. Once you have that set up, we'll just get this wire routed up into our engine bay near our battery. So, we just routed it in some loom behind our shutters here and we're really just following our diode wiring and I found a good spot right here to install our circuit breaker. It's just some plastic, so use the two included self-tappers, then strip the end of your wire and crimp on a small ring terminal.
I did kind of run outta wire at that point. That was about all I had left, so luckily I have some extra wire. If you don't have any extra wire then you could probably just choose a different route and mounting point. But, with my extra wire I also stripped back and crimped on a smaller ring terminal. That's gonna connect to our silver post here, so I'll have to take that nut off and get that installed. On the other end, we'll strip it back and crimp on a large ring terminal. That's gonna connect to our battery. So, we got that crimped on now and we're just gonna attach it to this post back here. I'll remove that nut, slide our ring terminal over and reinstall. Now that we have everything wired up, all that's left is to test it if you want to, and you would just need to hook up to your motor home and then hook up a multimeter and look for that 12 volts. Other than that, that's gonna do it for our look at and installation of the Roadmaster Charge Line kit on our 2020 Lincoln Navigator.
Customer Satisfaction Score:
96% were satisfied with this product
4% of customers were not satisfied
Ratings & Reviews
Worked as advertised. Keeps towed vehicle battery charged while using Patriot 3 breaking system. Customer service (Dominic) was excellent. Don't get too creative with wire routing. Though the wiring is long enough, there are limitations. I used an aluminum bracket from a rain downspout as a bracket - see picture.
Easy to install and Jeep battery is always charged arriving at the campsites.
I read that this is a must have for the Bronco. Evidently the battery can go dead while towing which could cause the Bronco to come out of Flat Tow damaging the transmission. This is cheap, easy to install insurance.
I never knew I needed this for flat towing. Sales rep helped me pick the right item. Shipping was in a timely manner and the price was fair.
Victoria H.
1/9/2025
That's awesome Ron! I will let them know you reached out.
Ron
12/20/2025
The Roadmaster accessories work great - the brake switch in the car is ideal for turning it on and off as required.
Works great, I was having trouble keeping my car battery charged while flat towing. I have to keep my car key in the acc position and its electronics and the power brake has to get plugged in the car lighter eating away at my battery so when I stop usually around the second stop and restart the car the battery is dead. With this charge line kit my battery stays charged! It’s a win. I hope I explained it properly
Easy install. Especially when installing in conjunction with the towed vehicle wiring kit. This will keep your battery charged due to battery drain from the turn signal/brake/tail lights on your towed vehicle.
Everything fit and works well. I’m happy with the etrailer instructions I installed everything myself didn’t take long at all
I ordered all the parts required to safely flat tow out 2017 Jeep Cherokee Trailhawk from etrailer.com. 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.
Roy
7/30/2018
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,
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
Jeffrey
11/19/2022
I have no regrets with this purchase. Items preform as advertised with no issues. I am very satisfied with Roadmaster and Demco products.
Exactly what was needed for keeping my battery charged while towing our jeep. Great price and happy with the result.
Easy to install and a must have to keep your battery charged on your towed vehicle.
Everything has been very reliable.
Everything was there for an easy instal lation
I had this professionally installed and it didn’t work the way I thought it should. When my tow vehicle was hooked up to my RV and the RV wasn’t running the Tow vehicles battery would feed back into the RV and the radio, back up camera, and GPS would remain on in the RV. This would ultimately drain the tow vehicle’s battery. I ended up replacing this with an RVi unit.
My installer, from you guys, did a GGreat job, no issues!
OVERPRICED AND UNDER DELIVERED!
You get about 15 feet of wire worth 50 cents per foot and it is BARELY enough to get from the front of the vehicle to the battery. It works, but just go to Homer Depot and buy a spool of wire and two circuit breakers and you'll have enough to wire both the RV and the tow vehicle for 50% less. Do Not Recommend
Perfect fit for 2025 ford maverick
Haven't towed the vehicle yet so I don't know that it works as it should but it was very easy to install with the video instructions.
I highly recommend this if you’re towing your vehicle behind a motorhome. We’ve gone across the country several times in the past year and I’ve never had a dead (or weak) battery on my Toad.
Nick S.
10/13/2025
This is definitely a part that is often forgotten, but makes the biggest difference! I am glad it is working well for you. Cross country?! Have you had any favorite spots you have hit?
First off the chat rep sent me a complete list of everything that I would need to flat tow a 2015 Equinox so I made the $[XX]+ purchase from their list. After two full days installing all the items needed in the towed vehicle I try and attach it to RV and the connection can not be made. The tow bar will not fit into the base plate attaching points. I immediately (7/21) open a chat to let them know that they recommended the wrong parts and the rep agrees that a mistake was made and says that they will upgrade the shipping of the correct tow bar without charge so that I can have the tow bar a full day before my trip to test the complete install. I follow through with them after getting my order confirmation and it states that expected delivery is 7/22 so even though I needed to purchase a second two bar and wait for a refund on the first tow bar I am satisfied with the handling of the situation and comfortable with the full day to test the parts. On 7/22 I track the package only to see an expected delivery date of 7/23 so I immediately open up a chat and they proceed to tell me that there is nothing that they can do because it is already shipped. Then they go on to tell me that I agreed to 2-day shipping, which I did not. The previous rep told me that they would upgrade the shipping because it was their mistake. The normal Free Shipping is only a two day delivery to my area so an upgrade would mean next day shipping. I requested a full copy of the chat transcript to see where I specifically agreed to 2-Day shipping and they did not send me the transcript. I definitely regret giving this company my money. Their staff needs a lot more training to say the least. First they recommend the wrong parts so they are no expert in their field. Then they force me to purchase the replacement part fully knowing that the mistake was theirs. Then they can not follow through on their agreement to expedite the replacement part. Finally when confronted they proceed to put the blame on the customer as well as shrug their shoulders and say that there is nothing that they can do. Save yourself time, money and aggravation. Shop somewhere else where your business is actually appreciated.
requires the enclosed solenoid be mounted within 8" of the battery--not ideal.
The kit is fine. The install was for a 1997 jeep wrangler with a new roadmaster base plate. The red wire was approximately 12 inches short for wiring to battery. Had to buy red wire so I would have one piece without extra splice.
Great fit for my 2025 Maverick
I’d highly recommend the charge line kit for anyone looking to tow for prolonged distances. No battery issues for me! Having the trickle charge gives me peace of mind as I tow. And one less thing to worry about is truly amazing. I used this for about 6 month on the road last year and am about to hit the road again. Love using products I feel confident with.
Victoria H.
3/21/2025
Thanks for your feedback Jenn! I'm happy to hear this adds more peace of mind to your adventures! Where to next?
Easy to install, keeps my F150 battery charged up while flat towing behind my Motorhome
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Condition: Like New
Notes: May have damaged packaging or minor cosmetic blemishes.
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Ken
2/27/2026
Great little product. Worked great while we needed it flat towing and the brake controller and lights were being activated. Now the Jeep is babied , trailered and enclosed.