How regenerative brakes work
HOW IT WORKS
Regenerative braking is a key technology found in hybrid and electric vehicles. Although this system serves the same basic purpose as a traditional one found in internal combustion engine (ICE) cars, its various components look quite different. Jack Shaw brings us a breakdown of how the systems work.
Regenerative braking is a kinetic energy recovery system that transfers the vehicle’s energy into electricity as it slows down. With a traditional hydraulic braking system, the friction between the brake pads and the discs produces large amounts of heat. Instead of letting this energy go to waste, regenerative braking puts it to better use.
When someone driving a hybrid or EV activates the brakes, electric motors recover the kinetic energy generated by the friction. This recovered energy is converted into electricity that charges the vehicle’s batteries, improving its performance, energy efficiency and overall range in one fell swoop.
Auto manufacturers have utilised four main types of regenerative braking systems over the years:
Electromagnetic An electromagnetic regenerative braking system connects the driveshaft to an electric generator, which uses magnetic force to restrict its rotation and slow the vehicle down while generating electricity. This can recharge EV batteries or power various auxiliar y functions, such as audio and climate control.
Flywheel A f lywheel regenerative braking system collects the vehicle’s kinetic energy and transfers it to a f lywheel, which is connected to the driveshaft through the transmission and gearbox. The spinning f lywheel supplies extra torque, providing a power boost.
Hydraulic A hydraulic regenerative braking system slows the vehicle by generating electricity with a compressing gas, usually nitrogen. Nitrogen pressurises the fuel and maintains its energy stores for long periods, but the pressurisation process needs to be faster for modern vehicles.
Electromagnetic/f lywheel The most common type of regenerative braking system for EVs is an electromagnetic/ f lywheel hybrid, which stores the electricity from the generators directly inside the flywheel instead of the batteries. The f lywheel acts as an additional mechanical batter y where energy can be recovered. It’s the most efficient and cost-effective way to store electrical power in EVs.
Since hybrids and EVs have electric motors, manufacturers can seamlessly install regenerative braking systems along the drivetrain or wheels. When the driver applies the brakes, the engine reverses itself to slow the vehicle rather than applying direct friction. The motor changes to become an alternator/ generator, continuing to rotate in the same direction but instead of driving, becomes driven.
Once the driver takes their foot off the throttle in a standard
