Mercedes-Benz of Princeton

Mercedes-Benz of Princeton

General 609-771-8040 | 2910 U.S. 1, Lawrenceville, NJ 08648

Ask a Technician: How Does Regenerative Braking Work?

Regenerative braking is a term that is increasingly seen in new vehicles. Initially introduced only on certain more expensive models, regenerative braking is now starting to become more widely available, and offers benefits through improved gas efficiency and performance.

Traditionally, when you brake in a car, a significant amount of energy is wasted. If you imagine the momentum with which the vehicle is moving, you will appreciate the amount of kinetic energy that the car is producing. When the car brakes, that energy would normally be lost, dissipating into the air as heat. As car manufacturers start to think about more environmentally responsible ways to build cars, they have acknowledged that there is an opportunity to reuse this energy elsewhere in the vehicle.

At the current time, regenerative braking is largely found within fully electric or hybrid vehicles. These are cars that are powered either solely by an electric motor or by a combination of a gasoline engine and motor. Even with hybrid cars, the electric motor may still sometimes be the only means of power for the vehicle at lower speeds so ensuring that the battery remains fully charged is critical to the performance of both these types of car. One way of keeping the battery charged is to recharge it when the car is not being used. Regenerative braking helps to charge the battery while the car is in use.

In a traditional braking system, friction between the brake pads and the brake rotors, and between the wheels and the surface of the road, helps bring the vehicle to a halt. Regenerative braking works in a very different way. When the driver presses the brake pedal of a hybrid or electric vehicle, the electric motor reverses. This causes the motor to run backwards, slowing down the car's wheels. While running backwards, the motor will also work as an electric generator, literally producing electricity from the kinetic energy, which is then fed into the battery.

Regenerative brakes work better at certain speeds. They generally work well around the city, where there is a lot of stop-start driving, and the vehicle is generally driven at lower speeds. Friction brakes are normally also fitted to hybrid and fully electric cars, so that when they are driven on the highway and or at speed, the vehicle is still able to brake effectively. This process is managed by a regenerative braking controller, which is able to determine when each system should be used. The braking controller also determines whether the electricity produced is used straight away, or stored.

With regenerative braking systems, drivers are very often able to determine how regenerative brakes should work via a number of presets. It is possible, for example, for regenerative brakes to be activated as soon as the driver takes his or her foot off the accelerator, even before he or she has pressed the brake pedal.

Overall, regenerative braking can capture about half of the energy that would otherwise have been wasted, and reuse it within the car's motor. It is estimated that regenerative braking can reduce fuel consumption by between 10 and 25 percent. For drivers, that's a double win, because regenerative braking helps save money and reduces the environmental impact. Keep reading our newsletter for more answers to your questions from the Mercedes-Benz of Princeton service department.