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Roadmaster Battery Charge Line Kit for Motorhomes

Roadmaster Battery Charge Line Kit for Motorhomes

Item # RM-156-75
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Roadmaster Tow Bar Wiring - RM-156-75
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This charge line connects to the battery in your RV to allow up to 15 amps to be transferred to your towed vehicle's battery during towing. Requires RM-156-25 be installed in towed car. 1-800-496-5010 to order Roadmaster accessories and parts part number RM-156-75 or order online at Free expert support on all Roadmaster products. Guaranteed Lowest Price and Fastest Shipping for Roadmaster Battery Charge Line Kit for Motorhomes. Accessories and Parts reviews from real customers.
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Roadmaster Accessories and Parts - RM-156-75

  • Tow Bar Wiring
  • Battery Charge Line Kit
  • Roadmaster

This charge line connects to the battery in your RV to allow up to 15 amps to be transferred to your towed vehicle's battery during towing. Requires RM-156-25 be installed in towed car.


  • Allows power from your RV's battery to be used to maintain the charge of your towed vehicle's battery while the car is being towed
    • Transfers just 15 amps to avoid overcharging the car's battery
  • Connects battery to 6-way or 7-way plug at the rear of your RV
    • Requires Roadmaster's vehicle battery line (RM-156-25 - sold separately) if no charge line is present in your towed vehicle
  • Includes 12-gauge wire, split wire loom, circuit breaker, and hardware
  • Made in the USA

156-75 Roadmaster Battery Charge Line Kit for Motorhomes

Installation Details RM-156-75 Installation instructions

Video of Roadmaster Battery Charge Line Kit for Motorhomes

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 for Motor Homes Installation - 2020 Coachmen Mirada Select Motorh

Hi there Coachmen owners, today in your 2020 Coachmen Mirada Select, we're going to be taking a look at and showing you how to install Roadmaster's charge line kit. This 12 volt charge line kit is going to provide you with the necessary wiring to have a charge line on your seven way connector. Your standard seven way is already going to have this here, but many of your motor homes don't come with a fully operational seven way connector. This is just the one circuit for the charge line circuit, which is necessary on some of your braking systems and also necessary if you want to charge the battery on your vehicle when you're flat towing it down the road. If you're going to haul any trailers with you as well, and you have batteries on those trailers, you'll want a charge line on there, especially if they have brakes. That'll keep the battery topped up on the trailer in the event that you do have a breakaway situation, that battery can be fully charged to apply the brakes.Our Mirada here didn't come from the factory with a fully functional seven way, so we had to add that additional wire for our Brake Buddy stealth braking system to work on our flat tow setup here.

It's an extremely straightforward installation, you're just running a wire from your battery back here. There's a circuit breaker that comes included with the kit to ensure that the wire remains circuit protected. But other than that, that is basically it. Follow along with me and we'll show you how to get her hooked up.We'll begin our installation by locating our batteries. They can be found underneath the steps, when you go to walk in your motor home.

We just lift up on the compartment door here and we've got our batteries here. Next we're going to want to mount our circuit breakers close to them as possible. So we just put it here on the back wall and use the included self-tapping screws to run it in. And you can use an eight millimeter socket with those self tapping screws. We then have two wires we need to run.

One is going to run right to the battery here. I recommend you wait to install this one until after you run the other one so that way the wire isn't live. You'll notice you'll have three different ring terminals here. These two on the circuit breaker are going to be the ones that have the smaller hole. The larger hole one is for the battery side.We're going to crimp on the small ones, so we can go ahead and connect them to the circuit breaker.

Just hold off on the battery side. And then the main portion of wire's what you're going to want to start with with this one so you know you've got enough length, so connect the ring terminal to it, attach it, and then begin running it towards the back towards your seven way connector. We just follow it right down the frame rail, zip tying it to any factory wiring on the way, because we know the factory wiring is already routed in a way where it's not going to get damaged, come close to anything excessively hot or any moving components.So we just follow this wire loom out and follow it all the way to the back to our seven way connector. This is going to hook to your charge line pin. Now the connector that was on our vehicle originally didn't have a charge line pin in it whatsoever, so we did have to replace the whole harness here that goes through the seven way connector in order to have all the pins that we need. On the connector we replaced it with, we used one here from Curt, and the black wire coming off of this connector is going to be your charge line wire. So you can see right here, we took the red wire that we had routed back from our circuit breaker, we used a heat shrink butt connector and crimped it onto the black wire. Just strip back your ends, crimp on your butt connector, and then use your heat gun to shrink it down.Now, if you are replacing this connector here with one from Curt, it's pretty straightforward. I highly recommend what you do is replace it one wire at a time because the wire colors are not likely going to match up with your motor home. Motor homes usually have their own proprietary wire color that just doesn't match up with our standard seven way. So all you would do then is just match up pin to pin. So if we're looking at this white wire here, this is the bottom pin here, so I would start with this bottom one, I would cut it, and then I would wire it to the wire on the connector for our new one that lines up in the same spot, and then just work my way around doing it one at a time to make sure that all the pins line up with the same holes once you've made your connections. And that completes our installation of Roadmaster's charge line kit on our 2020 Coachmen Mirada Select..

Customer Reviews

Roadmaster Battery Charge Line Kit for Motorhomes - RM-156-75

Average Customer Rating:  4.8 out of 5 stars   (55 Customer Reviews)

This charge line connects to the battery in your RV to allow up to 15 amps to be transferred to your towed vehicle's battery during towing. Requires RM-156-25 be installed in towed car.


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.


It was very simple to install

Pat - 08/27/2022


Quality of the product seems fine ..

issue is the 30 feet of wire included in the kit… Is this supposed to be a length sufficient to wire most RVs? How many 25’ RVs are capable of pulling a tow vehicle?

My RV is 38’ 10”… Because the wire included is worthless I was forced to purchase a 100’ roll (couldn’t find a 50’ roll) for $35.00…! Almost what I paid for the kit…. Bummer..


Still waiting to install it, but all the pieces are there and it should work well.


This is also a part i ordered for my tow behind car in order to charge the battery while pulling the car with the A class motor home on a long trip. The item is just what was described on the internet site. I haven't installed this item yet but it seems to be easily done with the instructions provided. I have ordered from Etrailer many time before and have always recieved great help from customer service and their whole crew. I will continue to do business with them in the future.

larry Brauer

Working great with no problems great product
Larry B - 09/20/2020


Works great and allows me to tow with vehicle stability turned on; no more death wobble! Installation instructions were clear and it fit perfectly.


Arrived early and installed easily however not enough protective sheathing provided to complete the job.


Since I did not know exactly what I needed, customer service outlined the products and helped me select what I needed!


This base plate was relatively easy to install (if you're handy and can follow written & video instructions), and is practically invisible when not being used for towing. Everyone at etrailer were helpful and knew exactly which parts were needed, even a year later when I asked about using the same base plate on a newer vehicle. The picture is just after install on my 2017 C-Max.


Roadmaster Battery Charge Line Kit for Motorhomes
# RM-156-75
Easy install, but suggest that the 12 gauge wire supplied was longer,or had a description as to the length on your website as it was too short for my 30ft MH. I had to purchase additional to complete the job. Otherwise, works like fine, and good price. Thanks, it should save my battery on my Equinox 2018 when towing.


Ordered 3 parts: RM-156-25; RM-156-75 and DW05745-10. All received very quickly, as is the case when I purchase from etrailer. More importantly, I get a 'live person' when I call for assistance and the service rep. is always knowledgable ( not an answering service that "will have someone call back". Time was spent with me answering all my questions and providing suggestions and opinions when I as for them, related to my project. Great company, great service - keep up the great work!


The battery charged kit connected on to our motorhome to charge the battery of our jeep has worked excellent and the installation also was an excellent job we are very happy with our installation.


Work as advertised - no issues


Nice kit as expected, Plenty of hardware and hook-up wire for our 2015 Dodge Dart. Would be nice to include $5 of snap on Red cover in the kit to help protect the hot leads.


Would highly recommend using etrailer for any trailer accessories that are needed. Very friendly staff and shipping is fast and accurate on delivery.


2015 Jeep Wrangler Rubicon Unlimited...kit was complete and easy to install. Still installed and working one year later!


Installed in my motorhome, works great easy to install following instructions provides. No more dead battery in the toad.


Everything there and arrived early


Products arrived as advertised, exactly as I expected with no issues. Easy install. I won’t hesitate to shop this site again, always a positive experience.


Works well. Keeps the battery charged in my tow rig.


Very easy to install. Everything needed is included.

After a year of using roadmaster nameplates and the electronic components to pull my 2019 jeep Cherokee I have been completely satisfied and have had no problems. I installed everything myself with help from etrailer staff and videos.
Daniel - 05/08/2020


Save my battery


It works, easy to install.


still n the box , did not use it . arrived after I went another route.


Simple to install if you know what you are doing.

Show More Reviews

See what our Experts say about this Roadmaster Accessories and Parts

  • Does Fuse of 2014 Honda CR-V Have to Be Removed When Flat Towing Even With Charge Wire
    Our # RM-156-75 which is used to charge a tow vehicle's battery when being flat towed wouldn't be enough to leave the fuse left in your 2014 Honda CR-V. Some of the depletion of the charge might be offset, but in the end you always have to go by what the manufacturer of the vehicle recommends.
    view full answer...
  • Where is the 12 Volt Trailer Tow Battery Fuse For the 7-Way on a 2016 Ford F-53 Chassis
    I looked through the owner's manual as well as some wiring schematic for your 2016 Ford F-53 chassis and there is no mention of a 12 volt trailer tow battery feed. After some additional research online it seems as if this circuit was excluded from the F-53 chassis but I am sure the dealer would be able to give you a definitive answer. With that being said, it may be best for you to just run your own charge line from the coach battery to your 7-way. This can be done with the Roadmaster Battery...
    view full answer...
  • How To Run a Trailer Battery Charge Line on a 2018 Ford F-150
    If the circuit for the 12 volt power to the trailer connector is not present on your 2018 Ford F-150 then you can easily run this yourself using the Roadmaster Battery Charge Line Kit part # RM-156-75. This kit would attach to the 12 volt power wire on the back of your connector and then it would get run up to the vehicle's battery. I have personally not heard of this issue before but if the dealer said the circuit was not present then I would proceed assuming this is correct. I however...
    view full answer...
  • Length of Roadmaster Battery Charge Line Kit for Motorhomes
    The Roadmaster Battery Charge Line for Motorhomes part # RM-156-75 is 30 feet long. It Includes 12-gauge wire, split wire loom, circuit breaker, and hardware
    view full answer...
  • Will Starting Vehicle with Roadmaster Battery Charge Line Kit # RM-156-75 Connected Damage Anything
    You would not need to worry about damage occurring if you started your vehicle with the Roadmaster Battery Charge Line Kit # RM-156-75 installed. There would be no need for a diode either. Having an additional 12 volt power source attached to your vehicle while it's running would essentially just be like having a more powerful alternator. Basically it would just be like having more amps present which would not hurt anything.
    view full answer...
  • Full 12 Volts Not Reaching Roadmaster Battery Charge Line Kit for Towed Vehicle
    I am not sure if you have already tested the battery charge line circuit on the motorhome's 7-way but if not this will be your next step. If you don't get 12 volts here then there is an issue with this circuit on your motorhome. Aside from tracing the wire back I don't have much to resolve this issue so easiest option would be to just run your own wire with the Roadmaster Battery Charge Line Kit for Motorhomes part # RM-156-75. If you do get 12 volts on the battery charge line circuit on...
    view full answer...
  • What Scenario Is the Roadmaster Battery Charge Line Kit # RM-156-75 Designed to Work In
    The Roadmaster Battery Charge Line Kit # RM-156-75 and products similar to it are designed to keep the battery of the toad vehicle topped off while being flat towed. Typically supplemental braking system draw power from the battery of the tow vehicle to operate which since it's turned off does not have the alternator keeping it charged. These kits are not designed to work in the scenario you described which is almost in reverse. If your concern is batteries getting drained when parked...
    view full answer...
  • Recommended Roadmaster Battery Charge Line Kit for Towed Vehicles Amperage Transfer at 12V
    It is very normal for the 12V charge line on a vehicle to provide only the voltage that is being provided by the alternator that is not being used by the vehicle itself. The 3.5 volts is not normal but just 3.5 amps would be normal when the vehicle is running. If you want the full 12V power, then you will need to run the # RM-156-75 which will give you 12 gauge wire and allow you to transfer 15 amps to avoid overcharging your Jeep battery.
    view full answer...
  • How To Turn On 12 Volt Charging System On 2017 Ford F-250 with Truck Bed Camper
    The best option we can offer to get the battery charge line circuit operational on a 2017 Ford F-250 with truck bed camper would be to bypass the factory circuit so you can send pull power to this at all times. This can be done with the Roadmaster Battery Charge Line Kit part # RM-156-75.
    view full answer...
  • How To Send Constant Power to 12 Volt Pin On Trailer Connector On 2020 Ford F-350
    The best solution as you alluded to is to bypass the factory "Smart Tow" trailer package which is what is responsible for only sending power to the 12 volt pin when the vehicle is in gear. This is actually pretty easy to do and we have a kit which will have everything you need to do so, the Roadmaster Battery Charge Line Kit for Motorhomes part # RM-156-75. In order to install this kit simply attach one of the wire leads to the battery and then to the circuit breaker. Once this is done,...
    view full answer...
  • Is It Okay To Run Battery Charge Line Circuit for 7-Way Inside Vehicle
    In order to add the battery charge line circuit on a 7-way trailer connector you can use the Roadmaster Battery Charge Line Kit part # RM-156-75 which comes with everything you need and most likely more wire than you'll actually need. In regards to the exact route you must take, there really isn't a set in stone way, whichever works best for your particular application. The important thing to note is to stay clear of moving parts or heat. If the inside of the vehicle works best for your...
    view full answer...
  • Installation of Roadmaster Charge Line Kit on 2014 Ford Edge and RV For Flat Towing
    Typically when a 7 way is installed initially on a tow vehicle the reverse light circuit is on the center pin. When you're installing the Roadmaster Charge Line Kit for Motorhomes # RM-156-75 you're going to want to install it on the center pin where the reverse light circuit previously was- you'll want to cut that wire completely off and wire in the new wiring directly.
    view full answer...
  • Can the Roadmaster Battery Charge Line Kit for Motorhomes Be Hooked Up To Power Distribution Center
    The Roadmaster Battery Charge Line Kit for Motorhomes part # RM-156-75 simply requires a power source capable of drawing 15 amps so whether you are hooked up directly to the battery or the power distribution center which is fed from the battery it should not matter. The rule about being six inches from the battery is in reference to the circuit protection but the power distribution center will still follow this standard.
    view full answer...
  • Charge Circuit of 2020 Newmar Bay Star for Flat Towed Vehicle
    Assuming that wire you found is a 12 volt circuit that is fuse protected like you mentioned you certainly could use it to charge the tow vehicle with the # RM-156-75. You should note that the charge circuit of a 7-way is actually the 1:00 pin of the connector as you are facing it.
    view full answer...
  • Troubleshooting Battery Charge Line Kit on 2018 Jeep Cherokee
    I can assume you are using the recommended Roadmaster Battery Charge Line Kits # RM-156-25 for towed vehicles and # RM-156-75 for motor homes. I've added links to installs of these kits for you to refer to so you can ensure your install followed the same process. If by "switched" or "unswitched" you are asking if the 12 volt circuit turns off when you turn off your RV, then it seems as if it is not switched. You will want to disconnect your 2018 Jeep Cherokee from your RV when you are...
    view full answer...
  • Comparing Roadmaster Battery Charge Line Kits
    I took a look at the manual for the Roadmaster Battery Charge Line Kit for Motor Homes # RM-156-75 as well as the manual for the Roadmaster Battery Charge Line Kit for Towed Vehicles # RM-156-25. The kit for towed vehicles specifies 14 AWG wire while the kit for motor homes specifies 12 AWG and I recommend sticking to that gauge wire on both, particularly because it includes the wire with the kit. As far as the breaker terminals there is not a significance in color difference because the...
    view full answer...
  • Vehicle and Motorhome 12V Charge Line Kits
    You can use Roadmaster Battery Charge Line Kit for Towed Vehicles Item # RM-156-25 for your 2017 Jeep Wrangler Unlimited. If there is no charge line on your RV then you will also need the motorhome side kit # RM-156-75.
    view full answer...
  • How to Keep Battery From Draining While Flat Towing a 2016 Ram 1500
    Since your 2016 Ram 1500 doesn't require the battery to be disconnected while it's being flat towed you can use a charge line to maintain its battery. The Roadmaster # RM-156-25 is what you will install in the Ram and # RM-156-75 will install in the RV.
    view full answer...
  • Will the Roadmaster Battery Charge Line Kit Charge the Battery With the Motorhome Off
    In order to determine if the Roadmaster Battery Charge Line Kit for Towed Vehicles part # RM-156-25 will charge your vehicle's battery with the tow vehicle off you simply need to test the 12 volt power pin in the 1 o'clock position on the vehicle side trailer connector. If you get power on this pin with the motorhome off then power will be sent to the vehicle's battery so long as the trailer connector is plugged in. If you get power to this pin only when the motorhome is running then you...
    view full answer...
  • Installing Battery Charge Wire Kit For Motorhome and Towed Vehicle Connection
    The Roadmaster Battery Charge Line Kit for Towed Vehicles # RM-156-25 should be installed to the center port of the 6-way trailer connection. If you have a different connection, let me know as most charge kits have this 6 wire connector on the towed vehicle and a 7-way on the motorhome. If you don't already have the charge line for your motorhome, then you will want to use the Roadmaster Battery Charge Line Kit for Motor Homes # RM-156-75 which will have you connect the new wire to the...
    view full answer...
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  • When Is Roadmaster Charge Line Kit # RM-156-75 Needed When Using # RM-156-25
    The Roadmaster Charge Kit part # RM-156-25 is designed to tap into the 12 volt power circuit that's carried from the tow vehicle to the towed vehicle through the wiring used for the lighting. If the trailer wiring at the rear of your 2013 Thor Palazzo already has the 12 volt circuit active then you would not need to use the # RM-156-75 but if it does not then you would need this kit as it comes with extra wire to run from the motor to the connector.
    view full answer...
  • Battery Charge Line Kit Recommendation for Flat Towing with RV Without 12 Volt Circuit Active
    Since the 7-way of your tow vehicle does not have the 12 volt accessory circuit active you'll need the charge line kit from Roadmaster part # RM-156-75 installed on the tow vehicle to complete that and then on the towed vehicle you'd need the part # RM-156-25 and you'd be set. The fuses of your Fit will still need to be disconnected.
    view full answer...
  • Charge Line Kit Recommendation for 2010 Buick Enclave Getting Flat Towed to Keep Battery Topped Off
    Yes, as far as a charge line kit goes for your 2010 Buick Enclave the Roadmaster kit part # RM-156-25 is your best and simplest solution. Basically it connects to the 12 volt accessory circuit of your trailer wiring and gives you a trickle charge to offset the draw of your Brake Buddy system. It will be enough to keep the battery working properly. I attached a couple install videos for this as well. If the trailer wiring accessory circuit on your tow vehicle is not active you'll also need...
    view full answer...
  • Why Does the Roadmaster Battery Charge Line Kit Come With a Red Wire Instead of Black
    I think you are talking about the Roadmaster Battery Charge Line Kits, part # RM-156-75 and part # RM-156-25 which are actually put together by Roadmaster. Generally speaking, automobiles use red for power which is why that is the color of the wire included with the kit whereas trailer's use back. That said, I can assure you this will not have any effect on performance and it won't hurt to use a red wire going to the circuit breaker and a black wire leaving or vice versa.
    view full answer...

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