Regenerative Braking in EVs – An Overview

Regenerative braking is a mechanism found on most hybrid and fully electric vehicles. It captures the kinetic energy from braking and converts it into the electrical power that charges the vehicle’s high voltage battery. Regenerative braking also slows the car down, which assists the use of traditional brakes. Electric motors, when used in reverse, function as generators and will then convert mechanical energy into electrical energy. Vehicles propelled by electric motors use them as generators when using regenerative braking, braking by transferring mechanical energy from the wheels to an electrical load.

In a conventional braking system, a car slows down due to friction between the brake pads and rotors. But this system is highly inefficient when it comes to conserving energy. Nearly all of the kinetic energy propelling your car forward is lost as heat when you apply the brakes. That’s a lot of wasted energy! 

With regenerative braking, the energy from your spinning wheels is used to reverse the direction of electricity – from the electric motors to the battery. All you have to do is remove your foot from the accelerator or, in some cases, press the brake pedal to activate regenerative braking. The electric motor not only acts as an electric generator, but it also helps slow your car down because energy is consumed by the wheels as they rotate the shaft in the electric motor.

Regenerative braking solves this problem of energy wastage by recapturing upwards of 70% of the kinetic energy that would otherwise be lost during braking. The amount of energy recovered depends on your car model and driving behavior.

Principle of operation

To understand how the regenerative braking system works, it is necessary to remember that every moving body has kinetic energy. When braking a car with an internal combustion engine, this energy is consumed during the contact of the brake pads and brake discs, erasing them, i.e. just “nowhere.” Electric vehicles are taking a more thoughtful approach to energy use. The recovery process is presented here as follows:

1. When braking starts, the electric motor changes its operating mode: instead of being powered by a battery, it starts to work as a generator, generating energy. At this moment, opposite currents appear in the rotor and stator windings.
2. The decrease in the speed of the vehicle occurs because a braking torque appears on the shaft of the electric motor.
3. The kinetic energy available before the start of braking is transformed into electrical and thermal energy.
4. The emerging additional electricity flows into the battery, thereby increasing its charge.

In a situation where the range of an electric vehicle is limited by the battery charge, any source other than the charging station that can generate additional energy is important. Therefore, regenerative braking DPT is a good and promising way to increase mileage. And 70% of the saved energy is a good indicator, given that just 10-15 years ago such losses were not paid attention to at all.

Advantages of Regenerative Braking

• It improves the fuel economy of the vehicle. The amount of fuel consumed can be dramatically reduced with this type of braking system due to the regeneration of energy.

• It allows for traditional friction-based brakes. A friction braking system is included with a regenerative system to ensure a vehicle is able to stop in time.

• It prolongs the charge of the battery. Once the energy is captured by the regenerative brakes, the energy is used to recharge the batteries of the vehicle. Because this energy would normally be lost, it allows each vehicle to experience a prolonged charge while driving.

• It reduces the wear and tear on the braking system. Because an electric drivetrain is part of this system, the greater efficiency given to the braking allows for a reduced level of wear on the brakes of the vehicle. With standard friction brakes, there is no way to accomplish this benefit.

Disadvantages of Regenerative Braking

• It offers a sliding scale of benefits. The effects of regenerative braking decrease with the speed a vehicle is traveling. At low speeds, friction brakes are required to bring most vehicles to a complete stop. That means there is still energy being lost.

• It offers a different feel to the driver. Regenerative braking systems feel different to drivers who are used to traditional systems. The brake pedal on the vehicle often feels soft, described as “mushy” by many drivers. Until you get used to the new system, some may have a lack of confidence in the capabilities of their brakes.

References:

• https://www.elprocus.com/what-is-regenerative-braking-system-working-its-applications/
• https://www.matfoundrygroup.com/blog/what-is-regenerative-braking-and-how-does-it-work
• https://en.wikipedia.org/wiki/Regenerative_brake

The following blog post has been written by Arounaachalesvarar B, an autoholic student from the SASTRA deemed University pursuing BTech EEE with specialization in electric vehicles. Aroun is interested in content creation and blog writing on automotive industry.

This post has been edited for grammar and other inconsistencies. To learn how you can contribute to content creation at Formula Bharat, visit www.formulabharat.com/careers.