Electric car regenerative braking: How does it work?
- Download the EVGuide Report, 2022
- How do brakes in a car work?
- How does regenerative braking work?
- What is an electric braking system?
- What is ‘one-pedal driving’?
- Vehicles with regenerative braking
You’ve no doubt heard the term, but just what is regenerative braking?
Regenerative braking is how an electric vehicle captures kinetic energy created when the car slows down, either transferring it directly to the electric motor or storing it in the battery pack for future use.
Although electric vehicles receive lashings of praise due to the obvious benefits — running a car on electricity is cheaper and far friendlier to the environment than a comparable internal-combustion engine (ICE) car — one issue keeps circling them like vultures eyeing off someone lost in the desert.
And that is, how to find a charger to keep them powered up.
Since EV-charging infrastructure isn’t quite where it needs to be at yet, especially in a country as expansive as Australia, there’s understandable concern around how to keep them sufficiently charged, especially during longer journeys.
Engineers far smarter than us have come up with technology to alleviate this problem in the form of regenerative braking, an ingenious process used in EVs — whether that’s a hybrid, plug-in hybrid electric vehicle (PHEV) or all-electric vehicle — where kinetic energy captured when the vehicle slows down is converted into power that the car can utilise.
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Regenerative braking can’t provide as much power as plugging an EV into an external source like a charging station, so it’s not a complete solution, but what it can do is continually top up your EV’s battery without you having to plug it in, which is a huge help in extending your driving range.
How do brakes in a car work?
In a traditional ICE car, the brakes are used to slow the vehicle down, with kinetic energy created by the car’s movement converted into heat via the friction of the brake pads, which then dissipates into the air — wasted energy, as it were.
How does regenerative braking work?
Like ICE cars, electric car brakes consist of a brake pedal, hydraulic brakes, and disc brake calipers that clamp the brake rotors to help you to stop.
Coupled with this is a regenerative braking system, which uses the motion of the wheels when the vehicle is slowing down to capture kinetic energy that is sent to the electric motor. This kinetic energy turns the motor shaft, with the motor acting like a generator.
The kinetic energy is converted into electrical energy by the motor, which is either instantly utilised or sent to the battery to be stored and used when needed.
Some EVs also have buttons or paddles which control the strength of the regenerative braking, with more sudden stopping naturally creating more kinetic energy than gently slowing down.
The sudden stopping is a boon for generating power, but be warned, it can be a jerky experience, and anyone eating food or drinking while it’s happening may want to think twice, lest they wind up wearing it.
What is an electric braking system?
Just to confuse things a little, there is an electric braking system that uses ‘brake-by-wire’ technology, where the mechanical and hydraulic components of traditional braking systems are replaced by electronic sensors and actuators to carry out the braking.
Does that have anything to do with regenerative braking? Not really, but at least you’ll be well equipped if you’re confronted with a pub trivia question regarding the difference between electric brakes and regenerative braking (if you do face that question, we might quietly suggest that you change pubs, pronto).
What is ‘one-pedal driving’?
For all intents and purposes, an electric motor that provides propulsion and a generator that creates electricity are mechanically the same, which is why EVs have a component that is typically referred to as a ‘motor-generator’.
In EVs, the process of regenerative braking kicks in as soon as you take your foot off the accelerator, the electric motor then switching over to act as a generator. The effort it takes to turn the generator requires the car to slow down significantly, meaning you may not even have to press down on the brake pedal to stop.
Thus, the term ‘one-pedal driving’ was born, since the accelerator acts as a kind of brake once you take your foot off of it, with the single pedal being used to speed up and slow down the vehicle.
While hybrids and PHEVs also have regenerative braking, full one-pedal driving is usually only available in fully electric cars.
Vehicles with regenerative braking
When it comes to Tesla, regenerative braking is standard in all of its cars. Other EVs that utilise regenerative braking include the Hyundai Kona Electric, Audi e-tron, Nissan Leaf, BMW i3 and Jaguar I-Pace. In fact, pretty much every vehicle with a hybrid, plug-in hybrid, or fully electric drivetrain uses regenerative braking in some form.