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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
Our Price: $60.01
Trailer Breakaway Kit
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Hopkins Engager Push-To-Test Trailer Breakaway Kit with Built-In Battery Charger - Top Load Single-axle,Tandem-axle 20400
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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. Great 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

  • Single-axle
  • Tandem-axle
  • Hopkins
  • Kit with Charger
  • Top Load
  • LED Tester

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 Satisfaction Score:

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   (668 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.


This battery kit is a perfect replacement for the battery that was on my 16 ft trailer to operate the brakes, in case of trailer breakaway. The charging light comes on when connected to my Tacoma pickup truck, which keeps the battery charged. This is a great product, and I'm very pleased with it.


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.



Cant tell you. I sold the trailer with the boat!


Would definitely purchase again! This is a good kit for setting up a break-away on your trailer. Make sure to mount it out of the way so that it doesn’t get impacted by any thing.


It arrived a day early, and it was exactly what I ordered! Go figure. Now I can put this in my ancient horse trailer instead of stacking rocks in the yard.


I am generally happy with Hopkins quality products. This one is one that I am very happy with. Quality is superbe.


Very good product. Clear instructions made installation easy. Solved my wiring problem.


Very easy to install and I feel it is made to last. I am very pleased with my purchase as well as the customer service provided by E trailer.


Simple installation , wiring diagram on the top cover. Easy Peasy!!


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.


Opened battery box and tabs that hold battery in place are broken

Etrailer Expert

Jenny N.


Oh no! I will have our Customer Service team contact you.


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)


This unit replaced the crusty 30 year old battery on my car trailer.
Easy installation if you do what I usually don’t. That is, read the instructions!!
The status LED charge indicator is a great feature.


Parts looked good and a fair price. I'll buy here again


Great product but wish it had better labeling and instructions for the wiring


Easy install if you read and pay attention to the directions. This was installed with a new 7 pin plug and there are different wiring configurations between utility trailers and larger rv type trailers; so pay attention to what you are reading and wire according to your project.


Thankfully I haven’t had to have an operational use of this. It was a straightforward installation and is easy to check the battery status. I would order this again, if needed.


i purchased this product to replace the same unit i purchased 5 years ago. The previous unit had sundamage and the top readout was no longer readable , the cover hinged were broken. easy replacement and works great


Fast shipping, pictures and items matched up to exactly what I needed. Thank You Again!


Perfect fit quick delivery.


While it was an easy fix, the wire length on the battery box is pathetic. The breakaway switch had long enough wires. If you get this, just run new wiring from the circuit board like I did.


Clean and easy.


Easily installed to replace the 13 year old unit


My breakaway came very fast and at a good price. I use e trailer all the time because they have what I need and get it to me fast.


Still working great

Show More Reviews

See what our Experts say about this Hopkins Trailer Breakaway Kit

  • 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....
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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...
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  • Parts Needed to Add Brakes to 1992 Coleman Arcadia Pop-Up Camper
    Based on your manual indicating 7" brakes it is probably a 2,000 lb axle. That should be a 4-bolt brake flange on the axle as well. Try checking your axle tag to see if you can verify this. The capacity may be listed, or it can be found with the serial number. You will need the following parts to add brakes: -Dexter Trailer Hub and Drum Assembly for 2,000-lb Axles - 7" - 5 on 4-1/2 # 8-257-5UC3 -Dexter Electric Trailer Brake Kit - 7" - Left and Right Hand Assemblies - - 2,000- to 2,200-lbs...
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  • Do You Carry the Pin for Engager BrakeAway Kits / Systems?
    We do carry replacement pins for the Engager Trailer Breakaway Systems. Item HM20010 has 7inches lead wires, and item number HM20014 has 44 inches lead wires. I will link you to both items below.
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  • Mounting the Hopkins Engager Push-To-Test Trailer Breakaway Kit on Horse Trailer
    It's pretty easy to mount the Hopkins Engager Push-To-Test Trailer Breakaway Kit with Built-In Battery Charger # 20400 on your horse trailer; the kit actually comes with self-tapping screws so you simply need to use those to mount it on an available space on your trailer. If you are having trouble finding an area to mount the kit you can also use the Weld-on Trailer Frame Mounting Plate for Hopkins Engager Breakaway Kit # HM20407 which you can weld onto your trailer frame to mount the...
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  • Determining The Parts Needed To Add Electric Over Hydraulic Disc Brakes To 2021 Grand Design 290BH
    We do offer a few disc brake conversion kits, but to confirm which one will fit your 2021 Grand Design 290BH I will need to know the axle rating of your axles, and which inner and outer bearings your current hubs use. To determine the axle rating you will need to check the axle tag located on the center of the axle facing rearward, and the axle rating will be on this tag. If you want to send me a picture of the tag that would be perfect. Now to determine which inner and outer bearing...
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  • Electric Trailer Brakes Engaging
    Thanks for the nice words and all that information! It certainly isn't normal that your trailer brakes are engaging without a brake controller though there are a couple of reasons why this can happen. My guess is a wiring issue on the trailer where the wires are making contact and 12 volt power is getting through to the brakes. So I recommend going over the wiring from your brakes and tracing it to see if there is an issue there. If need be you can replace with 10 gauge wire # 10-1-1. Or...
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  • Parts Needed To Add Electric Brakes to a Master Tow 80THD Tow Dolly
    We have all the parts you will need to add a set of electric brakes to a Master Tow 80THD tow dolly but they don't come in kits. I recommend installing electric brakes. It looks like Master Tow includes brake mounting flanges so you will need the following parts: Brake Assembly - Electric Trailer Brake Kit item # AKEBRK-35 - Sold as a pair Hub & Drum Assembly - Trailer Hub and Drum Assembly item # AKHD-545-35-K - Sold individually you'll need two. Trailer Wiring Junction Box item #...
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  • Parts Needed to Add Electric Brakes to 2020 Karavan Utility Trailer
    The first thing you will need to do in order to add brakes to your 2020 Karavan utility trailer is make sure you have a brake mounting flange. If you don't, you will need to take it to an axle shop and have a mounting flange installed. This will require identifying your axle. For example, if you have a 3,500 lb axle you would need the Brake Mounting Flange for 2-3/8" Round Axle # 4-35. If you do have a brake mounting flange, or you have one installed, the next thing you will need to do...
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  • 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.
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  • Parts Needed to Add Brakes to 2004 Fleetwood Pecos Pop-Up Camper
    Adding brakes to your 2004 Fleetwood Pecos Pop-Up Camper will require hub and drum assemblies, brake assemblies, 7-way wiring, and a breakaway kit. However, the first thing you need to do is check and see if you have a brake flange on the axle. If you do not have a brake flange, you will either need to weld one on or replace the axle. Either way you will need to identify the axle and capacity to do this. The best way is to check the axle tag. If you can send me or the axle manufacturer...
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  • Electric-Over-Hydraulic Actuator and Breakaway Battery Kit Recommendations for 3,500 lb Trailer
    Happy 4th to you as well, Jerry! Since you already have your 2017 Toyota Tundra set up for electric brakes you just need to add an electric-over-hydraulic (EOH) actuator and the breakaway battery kit. Here is what I recommend for your application: - Actuator for Drum Brakes # HS381-8066 - Actuator for Disc Brakes # HS381-8067 - Breakaway Battery Kit # 20400 Attached are some review and installation videos for you to check out!
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  • Dexter EOH Disc Brake Actutator Compatibility with 2018 Ford F-350
    The only modification needed on your F-350 to enable use of an electric-over-hydraulic trailer brake actuator like the Dexter # K71-650 (for drum brakes) or # K71-651 (for disc brakes) is installation of a trailer brake controller such as the Prodigy P3 # 90195. Not all trailer brake controllers are compatible with EOH actuators but the P3 has this capability that is easily selected on its main menu screen. The P3 also lets you store specific power settings that you can call up when needed...
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  • Replacing Suspension And Wiring On A 2006 Top Brand 7x18 Car Hauler Trailer
    Hey Dan I can definitely help with all of this. The # e43SR Trailer Axle that you were looking at comes with electric drum brake assemblies. In order to connect this to the 7-pin connector on your truck you will simply need a 7-way trailer harness such as part # 50-67-106. This comes with a 7-way plug with 18' of jacketed 7-wire. Since the electrical is trashed, you can use this to completely replace the trailer wiring for the brakes and lights. No separate actuator will be needed since...
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  • Parts Needed to Add Electric Drum Brakes to Trailer with 3500-lb Axle
    Starting with your Cherokee, the Prodigy P3 trailer brake controller # 90195 is an excellent choice. This is a superb controller both for performance and reliability. In your 4-pole equipped Jeep vehicle you will hard wire the P3 using the # ETBC7 installation kit. These two items will provide a complete 7-way wiring setup that will generate and deliver trailer brake power to the 7-way socket included in the kit along with all of the required trailer lighting signals. I linked both a helpful...
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  • Will Hopkins Engager Push-To-Test Trailer Breakaway Kit # 20400 Get Damaged from Sun Exposure
    We have not heard complaints from customers regarding Hopkins Engager Push-To-Test Trailer Breakaway Kit # 20400 like what happened with your old system. You could limit direct exposure to the sun somewhat by using # 20099 which is designed to mount with the panel facing to the side rather than up (though it doesn't have to be mounted that way).
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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.
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  • What is the Difference in Hopkins Engager Breakaway Systems 20099 and 20400
    Hopkins Engager breakaway systems # 20099 and # 20400 function the same way and have the same features. The main difference is in how they mount. Engager # 20099 is meant to be mounted on top of the frame with the LED indicator and test button facing up. Engager # 20400 was meant to be mounted to the side of the trailer frame so that its LED indicator and test button are also facing up. You will want to make sure the battery in the system you use is protected. That is why breakaway systems...
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  • Replacement Axle and Electric Brake Conversion on 2002 Karavan Boat Trailer KKRT-4100-78
    In order to replace your axle you will need to know your current axle capacity. In addition to the axle capacity you will also need to know the hub face to hub face measurement to match your current axle. Once you have this information you will be able to find a replacement, assuming one is available. Since you have square axles now and would be switching to a round axle you would also need new U-bolts. If you cannot find an axle with the same length and capacity the other option is to...
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  • Converting From Hydraulic Drum Brakes to Electric Brakes
    I could not find any type of photo of a Dico 15638 drum, but my understanding is they are 10" diameter x 2-1/4" wide, but if there is any potential interference with the magnet you would need to replace your hubs. If you would like to send a photo so I can take a look, please do. To add electric brakes to a 3,500 lb axle (if that is what you have) you will also need a 4-bolt Brake Mounting Flange # 4-35, a Breakaway Kit such as # 20400, wiring for your trailer as well as a brake controller...
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  • How to Convert a Trailer with Surge Brakes to Electric Over Hydraulic Brakes
    You can convert surge brakes to an electric over hydraulic braking system. To do this, you will need an electric over hydraulic actuator and a brake controller. For an electric over hydraulic actuator, I recommend looking at the Carlisle HydraStar units. If your trailer has drum brakes, you will want part # HBA-10. If your trailer has disc brakes, then you will want part # HBA16. I have also attached a link to all of our electric over hydraulic actuators for you to check out your options. The...
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  • Parts Needed to Convert From Hydraulic to Electric Brakes for 3,500 lb Axles
    Thanks for that info, and based on what you said, it sounds like you have a standard brake mounting flange like # 4-35 for a 3,500 lb axle. I do recommend just double-checking the inside diameter of your drum, as electric brakes for 3,500 lb axles fit drums that have an inside diameter of 10 inches. Assuming that is correct, we have exactly what you need to outfit your tandem axle trailer with electric brakes, which are the following parts: - Two (for both axles) of the Electric Trailer...
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  • Recommended Hub and Brake Assembly for 2,000 Pound Timbren Axle-Less Suspension System
    As long as you are not going over the 2,000 lb capacity then the Timbren Axle-Less Trailer Suspension System # ASR2000S02 will work well. You will need one like this that has the brake flange attached in order to use brakes. For a compatible hub and drum assembly, I recommend the # AKHD-545-35-EZ-K. This uses a 5 on 4-1/2 bolt pattern so you will want wheels that match the bolt pattern. For brake assemblies, I would choose self adjusting brakes like the Dexter Nev-R-Adjust Electric Trailer...
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  • What is the Recommended Breakaway Battery Size for a Single Axle Trailer
    The standard battery size for a breakaway system is 5 amp hours. I recommend the Hopkins Engager Push-To-Test Trailer Breakaway Kit with Built-In Battery Charger part # 20400 which is a complete kit that has everything you need. It also have a cool feature where you can simply press a button to see if your battery is charged and ready to go. It comes with the battery, switch, and mounting box.
    view full answer...

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