Regenerative braking: how does it work and what are its advantages?

Regenerative braking is a true guardian of autonomy and is now essential for any electrified vehicle.

Regenerative braking: how does it work and what are its advantages?

If you’ve ever been behind the wheel of a hybrid or electric car, you may have noticed a strange phenomenon the moment you let go of the accelerator. This strange phenomenon is actually not that strange since it is the regenerative braking, a function that you do not have on your thermal car, but which exists today on electric and hybrid cars. So what is this system? How does it work ? What are the advantages ? All the answers can be found in this article.

What is regenerative braking?

Maybe you have little memories of your high school physics lessons? If these are too vague, a very small reminder is in order. Energy cannot be created or destroyed, it can simply pass from one form to another. A principle that obviously applies to the subject of regenerative braking. When your car is in motion, energy accumulates. To stop the car, the kinetic energy that has built up obviously has to go somewhere.

For a traditional thermal car, the operating principle of braking is simple: friction is created between the pad and the brake disc, thus converting the stored kinetic energy into heat. Heat that is then dissipated into the atmosphere as the car slows down.

On the side of electric and hybrid cars, the system is more ingenious since kinetic energy is not totally released into the atmosphere in the form of heat. The kinetic energy that turns the wheels is transformed into electrical energy which is then stored in the vehicle’s battery.. Energy which is then redistributed to power the electric motor and run the car. In other words, it’s a somewhat contradictory principle: that of slowing down to generate the energy that will be used to move forward.

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How does regenerative braking work?

Before understanding how regenerative braking works, you must first understand where kinetic energy comes from. While driving an electrified car, the electric motor draws energy from the battery in order to operate and move the vehicle, creating the kinetic energy necessary for its movement.

When the vehicle slows down or the driver brakes, the process will be reversed. Kinetic energy will now spin the electric motor by the wheels, thus turning it into a kind of generator. This will oppose the rotation of the wheels and will have the effect of slowing them down. by transforming their kinetic energy into electrical energy. The electrical energy will then be stored in a battery where it will then be reused to power the car.

The regenerative system schematized on a Volkswagen Passat GTE

The regenerative system schematized on a Volkswagen Passat GTE

What are the advantages of regenerative braking?

The first advantage, in any case the most noticeable, is that, without touching the brake, only by taking your foot off the accelerator, your car will decelerate on its own and much harder than a conventional thermal car. In some cars, or even most electrified cars, we can manage the level of braking intensity. The more you increase the power of regenerative braking (often using paddles on the steering wheel) the more abruptly the vehicle slows down and the more electricity is created. This is also what Nissan counts on for the operation of its e-pedal on the Leaf.

Second advantage, the driver hardly has to press the brake pedal to slow down or stop the vehicle. Thus, by using little or no traditional brakes, their state of wear is much less important compared to a conventional thermal car. Be careful though, this is theory. Because in practice, it can also be very different. With less use, rust and contaminants can quickly build up and affect the brake caliper or the friction surface of the rotor. Brake components therefore wear out in reality, but in a different way.

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Third advantage, and it is certainly the most important, as stated above, regenerative braking makes it possible to recharge the battery while driving and therefore to increase autonomy. The autonomy announced by the manufacturers also takes into account the electricity created via the regenerative braking system. We can take the example of the Audi e-tron 55 which claims 435 kilometers of range with a single charge, but 120 kilometers come directly from energy recovery under braking.

Finally, note that regenerative braking encourages more responsible driving to avoid using the disc brakes suddenly. What perhaps push some drivers to review the way they drive.

Do all electrified cars have a regenerative braking system?

Today, few electrified cars are not equipped with this system. Even cars equipped with micro-hybridization, that is to say composed of a 48-volt battery and an alternator-starter helping the heat engine, have a regenerative braking system. The latter is obviously less pronounced, even almost imperceptible to the driver, but it allows the small 48-volt battery to be constantly recharged since it cannot be recharged otherwise. Today, many top-of-the-range cars such as the Audi A6 and A7 or the Mercedes Class E are equipped with this system.

On simple hybrids, those that do not plug in, such as the Toyota Yaris or the Kia Niro Hybrid, the all-electric range is very low compared to a plug-in hybrid, simply because the battery is much smaller. It recharges only via energy recovery when decelerating or braking.

Regenerative braking can also be used in motorsport, like in Formula 1 for example, but not only. Some EDPMs such as electric bikes or electric scooters are also equipped with this system in order to recharge their battery. Even more surprisingly, on the elevators, certain braking systems are assisted by an energy recovery system which comes into action during descents under full load, for example.

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The fact remains that today it is still impossible to do without a traditional brake completely, for many reasons, whether it be safety (emergency braking) or even brake management when the battery is full.


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