What is the Process of Regenerative Braking?
What Exactly Is Regenerative Braking?
Regenerative braking is a term that means exactly what it says. When regenerative brakes are engaged, the vehicle slows while also regenerating some of the electricity that was used to accelerate it. That electricity is recycled into the batteries, where it can be used to power the vehicle again in the future.This is in contrast to traditional brakes, which produce only heat and noise when slowing a vehicle. Unlike ICE vehicles, which only use conventional brakes, EVs use both conventional and regenerative braking.
How Does This Braking System Work?
When you use an EV's regenerative brakes, the electric motor that normally accelerates the vehicle switches over to work as a generator. Instead of using electricity from the batteries to rotate the wheels and accelerate the vehicle, the generator uses the vehicle's forward momentum and continued wheel rotation to generate electricity that can then be stored in the batteries. This process, in addition to charging the batteries, slows the vehicle.Mariner Bailey
Unlike traditional brakes, which activate only when you press the brake pedal, regenerative brakes frequently activate when you lift your foot off the accelerator pedal. Lifting your foot off an EV accelerator pedal can result in aggressive braking in some vehicles because this process is more pronounced in some than others.Every EV uses its braking systems in a slightly different way. Some EVs are designed to be driven without ever touching the brake pedal, with the regenerative brakes activating whenever you ease off the accelerator pedal and more aggressive braking occurring if you completely remove your foot from the accelerator pedal. Other vehicles use a milder form of regenerative braking in which aggressive braking occurs only when the brake pedal is pressed, and some allow you to switch between modes.
Why Do Electric Vehicles Use Regenerative Braking?
The primary goal of regenerative braking is to boost efficiency and range. An EV's range is limited without regenerative braking by the amount of charge stored in the car's battery when you unplug it and start driving. With regenerative braking, the vehicle can continue to produce power in excess of what is stored in the battery.This is because some of the battery power expended to accelerate the vehicle is recaptured and stored whenever the vehicle slows or stops, and that power can then be used to accelerate the vehicle again later. All of these actions contribute to an EV's increased range, even if only slightly.
Regenerative braking, in addition to increasing an EV's efficiency and range, has another advantage: it reduces pollution. While EVs do have traditional brakes, they are used far less frequently than in a comparable ICE vehicle. This means they don't need to be serviced as frequently and produce far less brake dust. According to Science Daily, because brake dust contributes to air pollution and can cause respiratory complications when inhaled, the less of it there is, the better.
Why Do EVs Still Use Conventional Brakes?
While EVs are designed to use regenerative brakes in a variety of situations, including stop-and-go traffic, each EV also includes a traditional braking system. This secondary braking system provides additional stopping power in an emergency and also takes over in certain situations, such as when an EV is stationary and must remain stationary.Full stops are another example. Some EVs use regenerative brakes to bring the vehicle to a stop, then engage traditional brakes to keep the vehicle stationary until it is time to move again. When used in this manner, the traditional brake system experiences almost no wear and produces no brake dust.
When rapid deceleration is required, the stopping power of traditional brakes can be combined with the stopping power of regenerative brakes. This type of use causes some wear, but not as much as an ICE vehicle driven in similar conditions.
Is Regenerative Braking Truly Beneficial?
Regenerative braking is always useful because it accomplishes a necessary task, but it is more efficient in some situations than others. While regenerative braking can and does increase a vehicle's range, the overall increase in efficiency is always dependent on factors such as driving conditions, how aggressive the driver is when accelerating and decelerating, and even the size and weight of the vehicle.When slowing a vehicle, generating electricity, and storing it in the batteries, regenerative braking is said to be 60 to 70% efficient. However, that level of efficiency does not translate into a 60 to 70% increase in range because regenerative brakes only charge the batteries when the system is in use. That is why driving conditions are so important in determining the effectiveness of regenerative brakes.
Stop-and-Go Travel
Regenerative brakes are far more useful in stop-and-go traffic than they are on long distance freeways. Because brakes are used much more frequently in stop-and-go traffic, regenerative brakes naturally charge the batteries much more than they would if the vehicle drove for long periods of time without slowing or stopping on an uncongested highway or freeway.Terrain
The effectiveness of regenerative brakes can also be affected by terrain. Driving downhill naturally allows regenerative brakes to charge the batteries more than driving uphill. Driving up and down hills on a regular basis will result in more recaptured energy than driving on flat ground, because some of the energy used to move the vehicle up each hill can be recaptured on the way back down.Vehicle Mass
The effectiveness of regenerative brakes is also affected by an EV's size and weight. Heavier vehicles require more energy to accelerate in the first place, so the regenerative brakes have more energy to recapture when slowing down. While regenerative brakes are used in vehicles as small and light as electric scooters, their impact increases as the vehicle's weight increases.various Modes
Some vehicles allow you to switch between regenerative braking modes, which can affect effectiveness. When you switch between these modes, the system regenerates more or less energy and the vehicle handles differently. Setting a less aggressive regenerative braking mode, for example, will allow a vehicle to coast longer when you take your foot off the pedal, but it will not be able to recapture as much energy in that lower mode.Rates of Recapture
In practice, EV drivers typically report recapture rates ranging from 5 to 30 percent. Lower rates are associated with lighter vehicles and extensive highway driving, whereas higher rates are associated with heavier vehicles and extensive city driving. So, while regenerative brakes are more useful in some situations than others, they still contribute significantly to the overall efficiency of EVs.
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