Regenerative brakes: how do they work? – Kelley’s Blue Book

If you’re shopping for a hybrid or electric vehicle, you may have heard of regenerative braking. If you’re wondering what it is and how it works, you’ve come to the right place.

What are regenerative brakes?

Regenerative brakes use electric motors rather than a traditional friction braking system to slow and stop a car. Hybrid and electric vehicles typically use these types of brakes.

With a traditional hydraulic braking system – usually disc or drum brakes – braking wastes energy. It takes the kinetic energy that drives your car and turns it into heat rather than motion. Although effective in slowing down a moving vehicle, friction braking wastes energy.

With regenerative brakes, the braking system captures this kinetic energy and transfers it to the car’s batteries. The system wastes less energy than it would with friction braking. The use of regenerative brakes makes it possible to preserve and restore the range of an electric or plug-in hybrid vehicle.

In a conventional hybrid, energy recovered from regenerative braking helps power certain auxiliary functions in the car, such as the audio and climate control systems. This relieves some of the load on the engine and electrical system and improves efficiency.

There is another type of regenerative braking called Hydraulic Power Assist. It generally only applies to commercial vehicles. Electric regenerative braking is the relevant type of system for the average driver learning about regenerative braking.

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What types of electric vehicles have regenerative brakes?

All electric and plug-in hybrid vehicles currently on the market in the United States are equipped with a regenerative braking system. Some conventional hybrids do this too, like the Toyota Prius.

Here are a few cars on the market today with regenerative brakes. This list is not understandable:

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Advantages

Energy recovered: Hydraulic brakes waste energy by turning kinetic energy into heat. However, regenerative braking feeds that energy into the car’s batteries and turns it into a little extra range.

Improved range: Regenerative braking does not add significant miles to your range. Yet these reclaimed energy gains can really add up when used liberally and consistently. Drivers of hybrids and electric vehicles know that every mile of battery life counts.

Reduced brake wear: The more regenerative brakes you use, the less you need to use traditional friction brakes. This means fewer trips to a service center for brake pads, rotors and shoes. With regenerative braking, some hybrids and electric vehicles can travel around 100,000 miles between braking services.

The inconvenients

You have to get used to: Regenerative brakes take a bit of getting used to, especially if you’re shopping for a used example of an older electric or hybrid vehicle. This technology is advancing, but regenerative braking sometimes has an odd feel that can be shocking to the driver.

Less reliable at high speed: Friction braking is a very old and very reliable technology. When you apply the brakes on a car equipped with hydraulic disc or drum brakes, the vehicle comes to a stop reliably and quickly. Regenerative brakes are not as good as friction brakes for emergencies where the car needs to come to a complete stop quickly. This is why hybrids and electric vehicles generally use both types of braking systems.

Low speed, low advantage: When you use regenerative braking in low-speed city driving, it does not generate enough energy to have a significant impact on your car’s range. For this reason, there is little benefit to using regenerative brakes when driving at low speeds.

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How Regenerative Brakes Work

Regenerative brakes work by reversing the electric motors that propel a car. It works like a generator and feeds power back into the hybrid or electric system to help replenish some range. These small increases in battery life can add up and improve efficiency over time when used regularly.

Drivers can activate regenerative brakes in different ways. Some hybrid and electric cars have a paddle near the steering wheel that activates the regenerative brakes. However, activation is seamless in most cars with regenerative braking. Applying the regular brake pedal with your foot allows the regenerative and friction brakes to work together to slow the vehicle. Cars with a particularly aggressive system can use regenerative brakes when the car is coasting. Sometimes called one-pedal driving, drivers can use the feature in a specific drive mode that emphasizes efficiency on long trips.

Although regenerative brakes use different engineering than friction brakes, they accomplish the same goal of slowing and stopping a moving car. Since it has the same effect as regular brakes, the brake lights always turn on when using regenerative brakes for safety.

For example, let’s say you drive a Nissan Leaf in e-Pedal mode. When you take your foot off the accelerator, the regenerative brakes automatically activate. At the same time, the brake lights at the rear of the car come on as they would if you were to press the brake pedal.

Brake and regenerate

Regenerative brakes are a great way to preserve the range of an electric vehicle and improve the efficiency of a hybrid. You can use them a lot to recover a lot of energy, or you can let them work in the background without changing your driving habits. Either way, you’ll be glad your next hybrid or EV has them.

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