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Hopkins Engager Push-To-Test Trailer Breakaway Kit with Built-In Battery Charger - Top Load

Hopkins Engager Push-To-Test Trailer Breakaway Kit with Built-In Battery Charger - Top Load

Item # 20400
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Trailer Breakaway Kit
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20400 - Top Load Hopkins Kit with Charger
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Breakaway system with built-in charger is designed to bring a trailer safely to a stop by activating its electric brakes should it become disconnected while being towed. Push-button tester lets you know if the rechargeable battery is fully charged. Lowest Prices for the best trailer breakaway kit from Hopkins. Hopkins Engager Push-To-Test Trailer Breakaway Kit with Built-In Battery Charger - Top Load part number 20400 can be ordered online at or call 1-800-940-8924 for expert service.
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Hopkins Trailer Breakaway Kit - 20400

  • Kit with Charger
  • Top Load
  • Hopkins

Breakaway system with built-in charger is designed to bring a trailer safely to a stop by activating its electric brakes should it become disconnected while being towed. Push-button tester lets you know if the rechargeable battery is fully charged.


  • Breakaway system activates your trailer's electric brakes if the trailer disconnects from the tow vehicle
  • Push-to-test battery feature offers fast and easy battery testing
    • Test button with LED lights clearly displays battery status
      • Green = charged
      • Yellow = charging
      • Red = low battery
  • Built-in charger automatically refuels battery while trailer is connected to tow vehicle
    • Charges at 1/2 volt below voltage supplied by tow vehicle to prevent over-charging
    • Shut-off feature activates when battery is fully charged
  • Top-loading case is easy to access from above
    • Weather-resistant construction protects battery from moisture and debris
    • Self-tapping screws included for simple mounting on your trailer's frame
  • Lockable lid deters theft (padlock sold separately)
  • Breakaway switch installs on your trailer's frame - drilling is required
  • Department of Transportation (DOT) compliant
  • 12-Volt rechargeable battery is included


  • Application: single- and tandem-axle trailers with electric brakes
  • Case dimensions: 4" long x 8" wide x 6-1/4" tall
  • Battery capacity: 5 amp-hours
  • Mounting hole spacing:
    • 7" From center of hole to center of hole horizontally
    • 1-1/2" From center of hole to center of hole vertically
  • 16-Gauge wires
  • 90-Day warranty

Note: A breakaway system is required by law in most states for trailers that are equipped with electric brakes and have a GTW of at least 3,000 lbs.

20400 Hopkins Engager Push-To-Test Trailer Breakaway Kit with Built-In Charger - Top Load - 5 amp/hrs

Installation Details 20400 Installation instructions

California residents: click here

Customer Reviews

Hopkins Engager Push-To-Test Trailer Breakaway Kit with Built-In Battery Charger - Top Load - 20400

Average Customer Rating:  4.8 out of 5 stars   (487 Customer Reviews)

Breakaway system with built-in charger is designed to bring a trailer safely to a stop by activating its electric brakes should it become disconnected while being towed. Push-button tester lets you know if the rechargeable battery is fully charged.


Following the installation instructions made the work fairly straightforward. The hole pattern for the case was as-advertised, so it fit perfectly where the old kit was installed on the trailer rail.


I was able to find hard-to-find lug nuts for my Haulmark trailer on etrailer; no auto parts store carried tis size. My break-away battery was dead, not surprising after 18 years of service. I also was able to cancel a wiring harness on my order, as I found the missing one in my garage.

All in all, etrailer is a pleasure to work with and has all the parts I need to keep my trailer in top shape.

It was great to have a working battery to power the electric brakes in the event I ped the trailer while driving.
John - 02/27/2022


The best costumer service I've received in years. Stacy was superb!!! and asked me all the right question about the parts I ordered. The "track your parts" was spot on. the only thing was I got my order in two days rather than three, as was promised. All parts were in stock and I received them in perfect condition, including an 8' trim piece. I don't normal fill out reviews, but this company went over and above!


All of my Hopkins products purchases through etrailer have been great products and great values. etrailer knows what they have and how an where to use them. Shipping and customer service are fantastic.

This trailer break-away braking kit got here fast and was as advertised.

Simple straight forward product. Still working great after a year in use.
John F - 12/25/2021


I bought these brake batteries when rewiring two old horse trailers. This is the third & fourth trailer I've rewired, so I'm pretty used to it by now. Everything about this product went together easily. Routing the wires on the trailer was another story, as usual.

I sold one trailer, but I've been using the other trailer infrequently for about a year now, and the brakes seem to be working quite well. I haven't had an occasion to test the breakaway battery out on the road, fortunately, but the little lights on the top indicate that it's maintaining a good charge, and the breakaway switch did lock up the brakes when I tested it in my shop.

BTW, I *love* pairing these with the Bargman coiled wiring plugs. They're so much nicer to use than straight wires.


I really wanted a 9 ah setup to insure ample power but I could not find one that also had a push button test feature so I decided I would just mount two and configure them to work together. It uses two, dpdt switches to switch the units on and off line either independently or together. This gives me assurance of ample power and a backup to each other..
One thing I'm going to do is run a diode isolated circuit to the cold side of the breakaway switch to the l.e.d. Break lights so if the trailer ever did come lose, it will also apply the break lights. The two diodes will keep the tow vehicles breaklight power from back feeding into the actuator's emergency stop circuit.


This breakaway kit was a good value and installed easily, but what I am most impressed with is the customer service orientation of When they determined that shipping of this product would be delayed, they immediately informed me and offered to send a comparable product that would ship immediately. Whenever I need anything for my trailers I don't even check other sources because I know from experience that will have the best price, fastest shipping and amazing customer service. And they are always able and willing to answer my questions and guide me in solving my trailer related problems.


I have not yet installed the breakaway kit, but I have never received anything but high-quality products from etrailer. I always go to them first.

Its installed on my tandem axle 7x14 cargo trailer, and it works beautifully! The installation was easy, and the results were far superior to the work originally done by the professionals. But everything I get from etrailer works great! I never go anywhere else for my trailer products.
Ed W - 11/18/2021


I had a few questions on how to install a product. I called and talked with Jamie. She was able guide thru the whole installation. Very cheerful, kind and never made me feel like I was a bother.


Good replacement for broken or worn out factory breakaway kit


etrailer provided very good service. They were responsive to my issue, sent out a return for the parts, inspected everything and replaced what needed to be changed.
I'm very pleased with the service we've received and their system has worked well for us in flat towing our jeep...


I spent a lot of time looking at and for an emergency trailer brake. I loved the etrailer website, it showed me good, better, best and clearly and quickly told me the costs and the difference between each. My unit arrived sooner than expected, in excellent shape, and included a battery which was a surprise! I have not installed it yet, but I am sure it will work great and do exactly what I need it to do. I have ordered from etrailer before and have never been anything but happy with my products.

Continues to work great. I have not had to use it thank goodness, but it works well each time it is tested.
Mitzi - 06/17/2021


Your representative answered my questions before I placed my order. The part came in, looks like a match. I will keep you posted as to how it works out. Shipped out as told, received as expected.


Fast shipping. Not installed yet but looks like nice quality at a reasonable price. Thanks for the speedy delivery.


Exceptional experience,
Was shipped
very quickly and arrived before scheduled .
Part fit correctly and was high quality . I’m going to purchase a few more to install on my other trailers .
This co is top notch !


Easy install if you are somewhat mechanically inclined. buy it you will like it.

Dg - 06/01/2021


Product works well
Applies power to
the electrical brakes if the cord is pulled
Easy to put the cord back into the switch
Used on a homemade trailer
That was made to carry bale barns
(hay feeder for horses)


The Break-away kit with charger and tester and a top mount display is a well made product that took maybe 4 minutes to replace and 8 more minutes to wire. The original was damaged when loading my trailer and no longer charged the battery making the breakaway system useless. I was looking for the circuit board to replace, but the entire unit was well priced and easy to replace. The only thing I would add to the kit are the needed butt splice wire connectors.

Outstanding product. The blade on my tractor hit the original break-away battery box. ordered this and fit perfect, no changes needed. Works great.
Darrell N - 01/01/2018


Excellent product. Wire and battery is the quality you want on your equipment. This was a direct replacement for a Peaque trailer I bought new 6 years ago that we use for our excavating company daily. I would recommend this product.


Battery Breakaway Box is of good quality & u can utilize the different cutouts for entrance/exit of wiring with common electrical wire knockout clamps , although wiring instructions on battery box need more clarification or better wiring instructions added to product . Also information on test circuit lighting functions of breakaway battery box would be helpful also .

I have linked a help article with more information on installing a trailer breakaway kit. The article specifically covers wiring a Hopkins breakaway kit with built in charger about half way through the article.
-- Etrailer Expert Victoria B - 11/05/2019


Price was right, installation and wiring was easy ad expected


Easy install, have purchased this before and probably will buy it again whenever I need another.


Quick processing, and delivery. reasonably priced . Adding this to my enclosed 16' trailer. Plan to mount it inside to keep it safe and secure. Impressed that it came fully charged. etrailer is my initial go to source for any trailer / motorhome /ATV related purchases. Great selection of parts and tons of how - to videos . Thank you for everything.

This kit has worked flawless from day 1. Battery is always fully charged. Use trailer 2-3 times a month. Gives great peace of mind knowing that it there and always ready.
don b - 02/06/2021


Great product, great service, best pric e!


This was a direct replacement and I purchased it based on price.

Show More Reviews

Ask the Experts about this Hopkins Trailer Breakaway Kit

  • Breakaway Battery Kit for Sundowner 2 Horse Trailer
    The Hopkins Engager Push-To-Test Trailer Breakaway Kit with Built-In Battery Charger - Top Load # 20400 will absolutely work with your Sundowner 2 horse trailer. I've attached some videos to assist and have also attached the diagram and an article to assist.
    view full answer...
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  • Installation of Breakaway Kit Switch for Electric Trailer Brakes on Gooseneck Trailer
    Hopkins Engager Push-To-Test Trailer Breakaway Kit with Built-In Battery Charger - Top Load # 20400 can have the pin mounted on the coupler. The angle should be as aligned as possible with the point you are connecting to and be slightly shorter distance than your safety chains. The pin will pull with force so the pin is designed to withstand that without breaking as is the cable. The length and angle are important because you want the trailer brakes to activate when the trailer becomes...
    view full answer...
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  • Is the Lid with Tester for Hopkins Engager Top Load Breakaway Kit Replaceable?
    The Hopkins Engager Push-To-Test Trailer Breakaway Kit with Built-In Battery Charger - Top Load # 20400 does not have a separate lid as a replacement part. The Breakaway switch is replaceable as is the battery, but to get that particular lid you need to replace the entire kit.
    view full answer...
  • Is Hopkins Engager Breakaway Kit Compatible with Over 30 Tandem Axle Trailer with 12 Gauge Wire
    I reached out to my contact at Hopkins and she said that the Hopkins Engager Push-To-Test Trailer Breakaway Kit # 20400 has been tested on a variety of trailer lengths and so it will be good to use on your tandem axle trailers. The heavier gauge wire that is shown in the chart you sent in will just help to ensure that as much power as possible is traveling as far as possible.
    view full answer...
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  • Trailer Breakaway System Operation And Troubleshooting
    The brakes shouldn't necessarily lock up, but the brakes should quickly bring the trailer to a safe stop. The weight of the trailer shouldn't matter if the breakaway kit and the trailer brakes are working properly. All trailer from utility to RV with a much larger weight capacity than the 5,000 lbs you mentioned use breakaways like the Hopkins # 20400. If it isn't functioning to a safe level, there is a need to fix something. It may be a ground, it may be a brake magnet, it may be...
    view full answer...
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  • Troubleshooting Shorted Out Brake Controller Connected to Breakaway System
    I'm sorry that this happened to your brake controller. I am happy to do research to help get this issues resolved. If when testing the breakaway system and the pin was pulled with the battery connected backwards. This would compromise the brake controller. When reaching out to my contact at Tekonsha we agreed that there may be a wiring issue someplace in the breakaway system. The combination of the wiring issue, combined with pulling the pin would certainly cause frying of the brake controller. The...
    view full answer...
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  • Why Does Amber Light Illuminate on Hopkins Engager Push-To-Test Trailer Breakaway Kit
    The amber charging light should not be always on so you are going to want to verify that the Hopkins Engager Push-To-Test Trailer Breakaway Kit with Built-In Battery Charger # 20400 is wired correctly. You will want to make particularly sure the ground wire is attached directly to your trailer frame. It may also be possible that somehow moisture got in the battery box and causing a short.
    view full answer...
  • Wiring Diagram for Trailer Breakaway Kit
    On this page (typically below the product links) there is a helpful link section that will have the install instructions fo the Hopkins Breakaway kit part # 20400 that you referenced. I also attached an install video that shows the kit installed as well as a diagram for trailer breakaway wiring as well. The white wire is the ground wire.
    view full answer...
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  • How to Wire Break Away Switch on Hopkins Engager Break Away System
    The black wire from the break away switch will connect to the blue wire from the break away box, as shown in the provided diagram. By 'brake wires' I'm assuming you're speaking of the wires connected to the brake magnets on your brake assemblies. One wire exiting the brake magnet could connect to the brake output circuit, usually a blue wire and the other would ground to the trailer frame. It doesn't match which goes where.
    view full answer...
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  • Breakaway Battery Continually Goes Dead
    The small breakaway battery shouldn't be going dead unless the breakaway switch is being pulled, there's a short in the system somewhere or the system has been incorrectly wired. The battery should be receiving a maintenance charge from the 12-volt power feed from the trailer connector on the tow vehicle. I would not recommend bypassing or altering the system at all. The breakaway system should have its own dedicated battery. I'll link you to an FAQ article that shows how the system should...
    view full answer...
  • Power Draw On Tow Vehicle Battery to Charge Hopkins Engager Push-To-Test Trailer Breakaway Battery
    The Hopkins Engager Push-To-Test Trailer Breakaway Kit with Built-In Battery Charger part # 20400 has a maximum power amp draw of 2 amps to charge the breakaway battery. The power draw is so low is will not drain the tow vehicle's battery. It will also only charge when the trailer is connected to the tow vehicle and the 12V circuit is active. On some vehicle's that does require the ignition to be turned on.
    view full answer...
  • How To Wire Up Hopkins Engager Push-To-Test Trailer Breakaway Kit
    In regards to the Hopkins Engager Push-To-Test Trailer Breakaway Kit part # 20400, there are only two wires with the black being power so it should be run to the positive battery terminal and the blue being brake output so it should be run to the brake output circuit. I have attached a wiring diagram you should use below.
    view full answer...
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  • How To Wire Hopkins Engager Trailer Breakaway Kit To Trailer
    Unfortunately you cannot wire the battery charger to battery of the Hopkins Engager Push-To-Test Trailer Breakaway Kit with Built-In Battery Charger # 20400 as it will not keep the battery charged. You will need to wire the battery charger to the constant 12v wire coming from the trailer harness. I included a video of the Hopkins Engager # 20400 being installed for you to take a look at.
    view full answer...
  • Weight of Hopkins Engager Push-To-Test Trailer Breakaway Kit
    The Hopkins Engager Push-To-Test Trailer Breakaway Kit with Built-In Battery Charger # 20400 only weighs four pounds, so it won't affect the hitch weight much at all. In regards to the brakes, this kit should not be used in place of your RV battery as its only function is for an emergency stop and this will help ensure the kit's battery is always fully charged. I have added links below to a video install and help article for you to check out as well of the Hopkins Engager Push-To-Test...
    view full answer...
  • Do I Need a Breakaway Battery Charger for My Trailer
    You need an electric breakaway when you have electric brakes on your trailer. A breakaway system is required by law in most states for trailers that are equipped with electric brakes and have a GTW of at least 3,000 lbs. Hopkins Engager Breakaway Kit with Built-In Battery Charger # 20400 would provide you with everything you need for a single or tandem-axle trailer. The battery and breakaway switch mount to the trailer. The battery is charged through the 7-way connection from your vehicle....
    view full answer...
  • How Many Charging Amps Does The Hopkins Engager Break Away Kit Draw When Charging The Battery?
    I spoke with Hopkins and their Engager Push-To-Test Trailer Breakaway Kit with Built-In Battery Charger # 20400 has a 2 amp charger. This will include a battery that has a 5 amp-hour capacity and has a built-in shut-off feature that activates when the battery is fully charged.
    view full answer...
  • Why Is There No Light on Hopkins Engager Push-To-Test Trailer Breakaway Kit With Test Button
    There should be a light on the Hopkins Engager Push-To-Test Trailer Breakaway Kit part # 20400 when you press the test button no matter the battery status. If ones does not appear, check your connections but you'll likely need a new unit as this would point to an issue with the circuit board. I recommend plugging the trailer into the vehicle for 15 minutes as this is what is needed to charge the battery completely. If you don't get any lights after that you know there is an issue with...
    view full answer...
  • Recommended Trailer Breakaway Battery Braking System with Integrated Charger
    The Hopkins Engager Push-To-Test Trailer Breakaway Kit w/ Built-In Charger - Side Load - 7" Wire # 20099 is the most popular option by far followed by the top loading version # 20400. This is my recommendation for the best option. Many trailer manufacturers utilize this breakaway kit because of its function and ease of use. I've attached a photo to assist with the installation.
    view full answer...
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  • What Causes a Melted Circuit Board on Trailer Breakaway System
    I am sorry to hear about the issue you are having with your new snowmobile trailer. I cannot say for certain that I know exactly what issue caused the circuit board to melt but I suspect there was an issue with power jumping circuits most likely due to improper soldering connections on the board itself. In order to really narrow down what the cause of the issue is, it would be wise to take the trailer into a service center for diagnosis. However, the fact of the matter remains that the...
    view full answer...
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  • Trailer Breakaway Kit with Charger for Trailers with Electric Brakes
    The breakaway kit pin when removed sends 12V power directly to your trailer brakes. Because you didn't have the pin in, the breakaway kit did exactly what it was designed to do for the trailer brakes. The battery box having damage sounds like the circuit board overheated and will need replaced. This definitely isn't normal operation and I don't know the cause of that. I recommend replacing the entire unit with the Hopkins Engager Push-To-Test Trailer Breakaway Kit w/ Built-In Charger...
    view full answer...
  • Will A Breakaway Kit Operate Properly Without An Auxiliary Battery
    It is possible to operate a breakaway switch from the trailer's main battery but it is not recommended. The breakaway kit may not function properly in emergency situations because the trailer's main battery has other accessories powered from it which may drain some of its power. The auxiliary battery that comes with breakaway kits such as part # 20400 will be kept at a full charge from the trailer wiring 12 volt power because it has a built in battery charger. Most states require by law...
    view full answer...
  • Comparing Hopkins Trailer Breakaway Kits 20099 and 20400
    Yes, both Hopkins trailer breakaway kits you referenced, parts # 20099 and # 20400, are complete and equivalent breakaway kits that differ only in the manner that they mount to the trailer. Part # 20099 mounts on the side of the trailer frame while part # 20400 can mount to the frame or to the trailer jack. I have linked in installation video for both kits as well as a helpful article.
    view full answer...
  • Comparing Hopkins Engager Breakaway Kits 20400 and 20099
    Pretty much the only difference between the Engager breakaway systems # 20099 and # 20400 are the designs of the battery boxes. Both function the same and have the same features. Engager # 20400 is meant to be mounted to the side of the trailer frame whereas # 20099 is designed more from the top of a frame. But ultimately you could install them anywhere there is space so I wouldn't say one is better than the other for you trailer.
    view full answer...
  • Recommended Trailer Breakaway Kit for 5th Wheel Trailer
    The trailer breakaway kits we currently offer are very similar to each other and differ only in a few available features and the location to which they are designed to mount. I recommend going with a kit that includes a charger, like the Hopkins Engager Trailer BreakAway Kit # 20099. This is currently our most popular trailer breakaway kit. Along with the built-in battery charger, this kit also features a nice push button tester that lets you know your break away system is ready to go....
    view full answer...

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