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Regenerative braking – what is it and how does it work?

Posted on 24/07/23 |

With more and more electric (and hybrid) vehicles on the road, is regenerative braking a mystery to you?

Regenerative braking is a way of taking the kinetic energy from a car’s momentum and converting this into electricity when you need to slow down.  This electrical energy can be used to recharge your hybrid or electric car’s battery.  On a normal car, braking simply wastes energy – but with regenerative braking, some of this otherwise unharnessed energy is able to be reused.

Regenerative braking systems are common on many modern cars.  On petrol and diesel models, it’s used to charge the battery that runs various ancillary systems in the car, meaning less work for the engine and less fuel burned.  In these cars, the system is virtually imperceptible to the driver, but in hybrid and pure-electric cars regenerative braking takes a more active and obvious role.  In these models, brake regeneration can help charge the big battery packs that supply electric drive motors with power.

How does regenerative braking work?

Electric motors can operate in two different modes.  With Drive selected, when you press the accelerator pedal, the motor will drive the wheels in a forward direction in order to move the car.  As you lift your foot off the accelerator pedal, the momentum of the vehicle turns the motor into a generator, inducing a current which is then fed back to the battery.

When you then press the brake pedal, the electrical resistance of the motor is increased, slowing you down faster but also generating even more current to top up the battery.

When the regeneration process kicks in, you’ll feel the car start to slow down.  This sensation can vary between models, though, as some manufacturers will have pre-programmed how much regenerative braking occurs when you lift off the pedal.  A number of cars also allow you to set the strength of the regenerative braking system yourself – this is usually done via a touchscreen menu or paddles attached to the steering wheel.

All cars still have conventional friction brakes though, so if you push the pedal hard enough – say, in an emergency stop – then the hydraulic system will kick in to slow you down as sharply as possible.  Again, different cars will require different amounts of force on the pedal in order to get the conventional braking system to kick in. 

Ack: Auto Express

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