Your questions answered

What is regenerative braking?

An easy guide to regen braking; what it is, how it works and why you needn’t be afraid of it

Brake regeneration is one of those things that sounds complicated, but isn’t. Also known as brake recuperation, this is a system that’s fitted to every electric and hybrid car and is designed to harvest excess energy produced when you brake or coast.

This energy can then be used to charge the car’s batteries and extend its range. It’s simple technology, too. When the electric motor is driving the car forwards, it’s putting energy into turning the car’s wheels.

But when you lift off the accelerator or brake in a car with regenerative braking, the process is reversed and the car’s wheels actually turn the electric motor. Effectively, the electric motor becomes a generator that's powered by the car’s own momentum.

However, for the electric motor to harvest that energy it must apply force, which it does by running in reverse. This is why, when you lift off the throttle in a car with regenerative braking, you feel it brake automatically without you hitting the brake pedal.

This is also why the technology often has more than one brake regen mode, since it’s very easy for manufacturers to program the electric motor to offer different ‘levels’ of pressure.

This means you can choose whether you want very heavy braking to maximise energy gain, or you can turn it off altogether if you don’t like the sensation of the car braking itself.

On top of this, many electric cars now use radar technology to introduce an ‘automatic’ mode to their brake regen systems, where the car will vary the recuperation force itself in order to keep a safe distance from the vehicle in front.

One-pedal systems, such as the e-Pedal driving mode on the Nissan Leaf, are further developments of brake recuperation. They simply dial up the brake force to the point where you needn’t use the ‘normal’ brake pedal at all when driving at slow speeds.

It's worth clarifying that all electric cars also have standard mechanical friction brakes, but if you want to make the most of your car’s range and also save wear on the car’s brake pads then it pays to use the regen system as often as possible.

In fact, many electric cars won’t apply force from those standard friction brakes until you hit the brake pedal quite hard, choosing instead to use the recuperation system for lighter braking in order to maximise the range.

Most electric car drivers find it feels very natural after a while, just like engine braking in a petrol or diesel car feels completely normal.

The only difficulty here is that the pedal can then have a noticeable change in response as it switches from regen to normal mechanical braking, so you’ll want to get used to the feel of the brakes and how they respond if you’re driving a battery car for the first time.

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