What Are RV Electric Trailer Brakes?

electric trailer brakes

Your tow vehicle comes equipped with brakes that are designed to efficiently stop it when necessary. Those brakes are designed for optimum performance up to the gross vehicle weight rating (GVWR) established by the manufacturer.

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When you attach a heavy trailer to that tow vehicle you now have a gross combined vehicle weight that probably exceeds the optimal performance specifications for your vehicle’s braking system. To maintain safety, it is important that your trailer has a supplemental braking system.

What Are RV Electric Trailer Brakes? 2

Electric trailer brakes are a supplemental braking system that provides braking force at the trailer wheels to assist the tow vehicle in stopping the tow vehicle/trailer combination. Those brakes are powered by and controlled by a trailer brake controller attached to the tow vehicle.

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That brake controller integrates into the braking system of the tow vehicle so when you press the brake pedal, the trailer brakes are automatically actuated. This allows the trailer brakes to work harmoniously with the tow vehicle brakes to control the speed of the combined rig. Let’s take a deeper look into trailer brakes to see how they work.

How Do Electric RV Trailer Brakes Work?

There are three main parts to a standard electric brake system on a trailer. Those consist of:

The Brakes

The brakes themselves are drum-style brakes located between the wheels and axles. Depending on your trailer, there may be brakes on one axle, two axles, or all axles. It is important to know how many axles have brakes on your trailer when choosing a brake controller. Each brake controller will have a limit as to how many axles it can power.

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The internals inside the brakes is very similar to a standard automotive drum brake. There usually have two pads, a manual adjustment knob, and a series of springs and parts to keep the pads in the correct position. The major difference is in how they actuate. In a car, the pads are tied mechanically to the vehicle braking system so that when you push the brake pedal in, the pads are forced out against the drum causing friction. That friction stops the car.

In a trailer electric brake system, there is a powerful electromagnet attached to the pad actuation hardware. When power is applied to that magnet, it sticks to the face of the drum. If the trailer is in motion, that face will be rotating. The magnet will stick to the rotating face and the rotational force will push the brake pads out against the drum surface.

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The magnet has a friction surface on it as well, which allows it to slide on the drum surface. The more power that is applied to the magnet, the harder it will stick to the drum surface which in turn creates greater pad pressure and more stopping power.

The Wiring

The brakes are connected to the tow vehicle through a standard series of wires. These wires usually connect into the tow vehicle’s electrical system through a standard 7-pin trailer plug. On the tow vehicle side, all the wiring for power and sense of the brake pedal is usually pre-installed from the factory and tied together into a trailer brake controller plug.

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The brake controller will plug directly into that port and automatically provide all the functions necessary to operate your trailer brakes. If your vehicle was not pre-wired for this, adding electric trailer brakes will require you to install a 7 pin plug and manually do any wiring to connect the controller into your vehicle’s wiring harness.

Trailer Brake Controller

The trailer brake controller is the brain of the operation. When you press the brake pedal, it senses that and draws power from the tow vehicle’s electrical system and sends it through the wiring back to the brakes, actuating them and slowing the trailer.

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Brake controllers have one main function, to vary the amount of power to the brakes which in turn varies how hard they stop. The most basic controllers are accomplished with a simple power knob or slider to adjust the power. Whatever you set it is what the controller will do.

More sophisticated controllers will allow you to set a maximum gain but then include user-selectable pre-programmed algorithms based on trailer size and weight to apply the brakes in the most efficient way possible. Some also include velocity sensors which detect how quickly the tow vehicle is stopping and then adjust the braking force to the trailer to match.

What Is The Maximum RV Weight Electric Brakes Can Handle?

Electric trailer brakes are a supplemental system to assist your tow vehicle in stopping your combined vehicle. The brakes themselves are braking units that are designed to meet specific requirements for their size and type. They are typically matched to a specifically sized axle that is capable of carrying a specific weight.

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Those axles are then combined to carry the total trailer weight. So, a 5,000 lb axle will have brakes capable of efficiently handling 5,000 lbs. A 10,000 lb trailer would require two of those axles with brakes on each wheel. While there is theoretically no limit, you just add more axles and brakes to carry a heavier load, in practice, you will run into issues.

The biggest one would be having a brake controller to run the system. Most brake controllers can only power a specific number of brakes at one time. Most quality controllers are limited to 4 axles. Ultimately, that will limit the maximum weight of the trailer.

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Each state does set braking requirements for trailers which are based on trailer weight. These rules can dictate requirements such as within a specific weight range the trailer must have brakes on both wheels of a single axle while at a heavier weight there must be brakes on all wheels on all axles. For more details see this table published by the RVIA.

Do RV Electric Brakes Use A Drum Or Discs?

Standard electric brakes are drum brakes. To have a disc braking system you would need to switch to an electric-over-hydraulic braking system. While both systems are powered by electricity, usually from the tow vehicle, they differ dramatically in their mechanics.

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Unlike electric drum brakes which create their stopping power with the friction generated by a variable electromagnet, electric-over-hydraulic brakes use electricity to power an actuator that pressurizes a hydraulic system which then clamps the disc brake calipers down on the pads.

There are brake controllers on the market that can operate either system, but there are some which are system-specific. Make sure you confirm the controller you are considering can handle the specific type of brakes your trailer has. If you’re planning on switching types down the road, choosing a controller that can handle both will save you some money and installation time.

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How Do You Know Your RV Electric Brakes Are Working?

There are a couple of ways to know if your electric brakes are working.

  1. Connect your trailer to your tow vehicle and start it up. When you press the brakes, your brake controller should show a number. Many, but not all, controllers will show an error or “NC” for “not connected” if the controller senses an issue or does not see that the brake circuit is connected. If you get a number on the display, they are likely working.
  2. If your brake controller indicates everything is connected and working, have someone stand near the trailer wheels that have brakes as you depress the brake pedal. You should hear a noticeable humming sound coming from the wheels when the brakes are applied. If you hear that, the brakes are likely working.
  3. Adjust your brake controller for maximum boost. Tow the trailer forward at a low speed and lightly touch the brake pedal, just enough to get the brake lights to turn on. The brake controller should show a boost value. If you can feel the trailer tug on the tow vehicle, the brakes are working. Alternatively, you can pull the manual actuation lever on the brake controller to activate the brakes. Again, if you feel the trailer pull on the tow vehicle while in motion then the brakes are working.
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Do I Need To Adjust My RV Electric Brakes?

Most modern electric braking systems are self-adjusting but you may still need to do specific things to activate the self-adjustment features, or even manually adjust them yourself. There are three types of electric braking systems commonly found on RV trailers.

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  1. Forward self-adjusting brakes will automatically adjust as you drive the trailer forward and apply the brakes. This is the most common direction the trailer will move so they will always be adjusted provided they are properly maintained and in proper working order. If they are out of adjustment, it’s likely they are worn out and need replacement. One of the drawbacks of forward adjusting brakes is they tend to wear faster than other braking systems. If they are not stopping with adequate force, try manually adjusting them or disassemble them for an inspection and replace any worn or failed parts.
  2. Reverse self-adjusting brakes will automatically adjust as you drive the trailer backward and apply the brakes. Until recently, these were the most common brakes installed on trailers. Reverse adjustment tends to be fairly unreliable. For it to work properly the brakes have to be in tip-top mechanical condition and the proper amount of force has to be applied when braking in reverse. If either of those conditions are not met then proper adjustment may not occur. In that case, manual adjustment will be necessary.
  3. Manual adjustable brakes. These brakes can only be adjusted by manually removing the adjustment port dust cover on the brake housing and rotating the adjustment dial with a flat blade screw driver.

Regardless of the braking system you have, you should do a brake test upon returning from every trip. This can easily be done as you head down the campground roads to your campsite or near your home as you return.

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Do it on arrival so you can make necessary adjustments or repairs before departing on your next trip. Double-check operation as you depart to make sure everything is working correctly, especially if you did any work on the brakes between trips.

Can You Back Your Trailer Up With RV Electric Brakes?

Yes, you can back up your trailer with electric breaks. There are two important things to remember when doing so.

  1. Most electric braking systems on trailers self-adjust when the brakes are applied in reverse. It is generally good practice to intentionally back up and brake with the brakes on a higher setting to keep them in proper adjustment. If your braking system has forward self-adjusting capabilities they will not self-adjust while backing up.
  2. When backing up during normal travel or when navigating a campsite, it is often beneficial to adjust the braking force to a lower level on the brake controller. This is especially true when the ground is level. Having the brakes on a high setting while backing up can cause uncomfortable or rough jarring between the trailer and tow vehicle. Turning the brakes down will minimize these problems and allow you to maneuver tight spaces more smoothly.
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Are RV Electric Trailer Brakes The Same As Breakaway Brakes?

Both electric brakes and the breakaway brake system on a trailer rely on the same braking mechanism to slow the trailer, but they operate the system in different ways. In the case of normal “trailer brakes”, the power for the brakes is provided by the electric brake controller which draws that power from the tow vehicle.

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The electronic brake controller actuates the brakes when the driver depresses the brake pedal and it is capable of modulating the braking force depending on the controller settings, controller program, or rate of deceleration of the tow vehicle. In the case of a breakaway braking system, the “controller” is a simple pull switch that is located on the trailer.

It is tethered to the tow vehicle via a wire. If the trailer separates from the tow vehicle, that wire gets pulled and activated the breakaway system. That system acts as an on/off switch for the brakes so when it is activated, the brakes are applied at 100%. Because the trailer has presumably separated from the tow vehicle, the power for the breakaway system is provided by a battery located on the trailer itself.

That may be the house battery, or it can be a small dedicated battery designed specifically for breakaway systems. Regardless of the power source, once activated the brakes will remain on until the battery dies or the breakaway switch is manually returned to the off position.

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