Regenerative braking: harnessing the efficiency of electric vehicles

Driving an electric vehicle (EV) offers a whole new experience compared to driving an internal combustion engine (ICE) vehicle, and one of the standout features lies in how it brakes.

If you remember high school science, you’ll know that energy cannot be lost; but it can be converted into another type of energy.

Traditional braking stops an ICE vehicle moving by applying huge amounts of pressure onto a brake drum or disc using the brake pad. This turns the kinetic energy of the moving vehicle into heat (and a lot of brake dust!). Essentially, energy is wasted.

An EV, whether it be a battery electric or a hybrid car, does something very different. Instead of losing all that kinetic energy, an EV recuperates it via the electric motor and stores it back into the lithium-ion battery.

If you remember playing with a dynamo toy as a child, you might remember turning a hand crank or spinning it to produce electricity to light up the toy, for example.

The motor inside the dynamo works by converting the kinetic energy from cranking or spinning the handle into electricity – the opposite of an electric motor which takes electricity from a battery and turns it into kinetic energy to move an EV.

Regenerative braking in an EV takes this concept one step further by using electrical resistance to slow the motor down.

When you put your foot on the accelerator of an EV, the electric motor uses more energy to drive the car forward.

When you take your foot off the accelerator pedal, the motor’s resistance increases, and electrical energy is created and stored back into the battery for re-use.

Regenerative braking has several benefits that improve the driving experience as well as the vehicle’s driving range and prolongs the life of the battery.

• Energy saved, not energy lost: One of the primary benefits of regenerative braking is its ability to save energy that would otherwise be wasted during the braking process. This energy is captured and stored in the battery, making it available for use in the future, thus increasing the overall efficiency of the vehicle.
• Smooth driving experience: Additionally, regenerative braking contributes to a smoother driving experience, as it eliminates the sudden jolts and jerks that are often associated with traditional braking systems. By seamlessly transitioning between acceleration and deceleration, regenerative braking provides a more comfortable ride for both the driver and passengers.
• Carmakers can control braking levels: Moreover, carmakers can control the braking levels of regenerative braking systems, allowing them to fine-tune the vehicle's performance according to their specifications. This level of control ensures optimal braking efficiency and enables carmakers to tailor the driving experience to meet different drivers' preferences.
• Customised driving experience: Some carmakers give drivers the ability to control the regenerative braking levels themselves. This not only allows drivers to customise their driving experience but also encourages a more interactive relationship between the driver and the vehicle.
• Less wear and tear on brake pads: Regenerative braking also has a positive impact on the longevity of brake pads. Traditional braking systems rely on friction to slow down the vehicle, resulting in significant wear and tear on the brake pads. However, regenerative braking reduces the reliance on friction, thereby minimizing the wear on brake pads and increasing their lifespan. This saves drivers from the hassle and expense of frequent brake pad replacements and contributes to the vehicle's sustainability.
• Increased driving range: Regenerative braking significantly increases the driving range of electric vehicles. By harnessing the energy generated during the braking process, regenerative braking effectively extends the amount of distance that can be traveled on a single charge. This is particularly beneficial for electric vehicles, as it addresses one of the main concerns associated with their limited range.
• Prolonged battery life: Also, regenerative braking is known to positively impact the battery's lifespan1. By reducing the strain on the battery and optimising its usage, regenerative braking can help extend the battery's overall lifespan, thus increasing the longevity of the vehicle.

Various EVs have different methods of implementing regenerative braking.

Some carmakers, such as Tesla, control the level of regenerative braking based on the State of Charge (SoC) or the temperature of the battery.

For example, if the battery is cold or close to full, the level of regenerative braking is decreased.

Other EVs allow the driver to control the level of regenerative braking.

Some do this via paddles behind the steering wheel, and others have a switch or button that allows the driver to choose between a number of pre-set levels.

Some EVs allow the driver to turn the regenerative braking off entirely, allowing it to “coast," and others allow the driver to select a strong level known as one-pedal driving, in which the car slows to a stop without using the traditional brake.

Depending on EV settings, regenerative braking can take a bit longer to act.

This is why EVs still have traditional brakes, and drivers must be ready to use the traditional brakes at all times.

One cool feature that sets certain EVs apart from their ICE stablemates is the concept of one-pedal driving, which allows drivers to effortlessly decelerate and bring their vehicle to a halt without putting the foot on the brake pedal.

One-pedal driving not only adds a touch of futuristic elegance to the driving experience but also provides several practical advantages.

One of these is enhanced safety because it invites the driver to plan their stops sooner, by simply lifting the foot off the pedal.

Because acceleration and deceleration are controlled via a single pedal, drivers have better control over their vehicle's speed and movement, making the overall driving experience more intuitive and efficient.

It is important to note that there are certain scenarios where one-pedal driving may not be the safest option.

For instance, when driving on icy or slushy roads, the traditional braking system may be more effective in maintaining control and stability.

Additionally, if the car is filled with a significant amount of heavy baggage or cargo, the added weight may affect the performance of the one-pedal driving system, necessitating the use of the traditional braking mechanism.

On very steep roads, the use of one-pedal driving may not be ideal as it may not provide the necessary control and precision required for navigating descents.

In these specific conditions, it is crucial for drivers to exercise caution and rely on the appropriate braking methods to ensure their safety and the safety of others on the road.

Always be ready to use the traditional brakes under any circumstances.

Nevertheless, one-pedal driving highlights advancements in EV technology. With its ability to offer improved safety, enhanced control, and a more intuitive driving experience, one-pedal driving can change the way we navigate our roads and enjoy our vehicles.

Source:

1. Chidambaram RK, Chatterjee D, Barman B, Das PP, Taler D, Taler J, Sobota T. Effect of Regenerative Braking on Battery Life. Energies. 2023; 16(14):5303. https://doi.org/10.3390/en16145303