Electric Bike Energy Regeneration: How Does It Work?

Electric bikes are a great way to get around, but can they regenerate? In short, electric bikes do not currently have a system for recharging while riding. However, some electric bikes are equipped with regenerative braking, which captures energy lost during braking and stores it in the battery. This technology is still in its infancy and is not widely available on the market. So, while it is possible for electric bikes to regenerate, it is not yet a common feature.

Regenerative braking

Additionally, the mid-drive arrangement, which is common in electric bikes due to its ability to use reduction gears, does not allow for regenerative braking due to the freewheel.

Despite these limitations, some companies are developing electric bikes with regenerative braking. For example, ThirtyOne's VAEs, a Toulouse-based company, has developed a hybrid bicycle that recharges on deceleration, whether downhill or backward. This bike incorporates the BionX conversion system, which offers four regenerative modes for different slope gradients.

Direct-drive motors

Electric bikes can be equipped with direct-drive hub motors, which allow for regenerative braking. This feature captures some of the energy lost during braking and stores it in the battery. However, direct-drive motors are not typically found in most electric bikes on the market, as they are very heavy compared to other types of motors.

Regenerative braking, also known as KERS (kinetic energy recovery system), is not currently an efficient or practical option for electric bikes. While it does not damage or wear out brakes, it requires a specific type of motor and has limited braking force.

The ThirtyOne VAEs, a Toulouse-based company, has developed a hybrid bicycle that recharges on deceleration, whether downhill or backward. This bike incorporates the BionX conversion system, which offers four regenerative modes for different slope gradients. However, it is estimated that the bike would need 300 kilometres of continuous downhill riding to fully charge, which is not practical.

Overall, while direct-drive motors enable regenerative braking in electric bikes, they are not widely used due to their weight and the limitations of the current regenerative braking technology.

Kinetic energy recovery system (KERS)

Regenerative braking, or Kinetic Energy Recovery System (KERS), captures some of the energy lost during braking and stores it in the battery. This technology is still in its infancy, and most electric bikes do not use it because it requires a direct-drive motor, which is heavier than the motors found in most electric bikes. These direct-drive motors also have the disadvantage of not being able to produce high forward torque and, therefore, not being able to produce high inverse torque for braking.

KERS is activated manually via the controller and features four regenerative modes, ranging from gentle slopes to very steep descents. Some electric bikes with KERS are estimated to be fully charged after 300 kilometres of downhill riding.

Although KERS is possible, it is not efficient or practical for most electric bikes. However, some promising electric bikes with KERS are being developed, such as the Pi-Pop.

Electric bikes with regenerative braking

Regenerative braking is a concept that captures some of the energy lost during braking and stores it in the battery. This feature is only available on electric bikes with direct-drive hub motors. While regenerative braking does not damage or wear out the brakes, it is not an efficient or practical option for most electric bikes because it requires a direct-drive motor, which is heavier and less powerful than other types of motors.

Regenerative braking is also uncommon in mid-drive electric bikes due to the freewheel, which does not allow for regenerative braking. Hub motors, on the other hand, are the only arrangement that would make regenerative braking possible, but they have low forward and inverse torque, resulting in poor acceleration and braking force.

Some electric bikes with regenerative braking include ThirtyOne's VAEs, a Toulouse-based company that has developed a hybrid bicycle that recharges on deceleration, and electric bikes with the BionX conversion system, which has four regenerative modes for different slopes. However, most electric bikes on the market do not have regenerative braking as the technology is still in its infancy.

RPM situation in electric bikes

Regenerative braking, also known as KERS (kinetic energy recovery system), captures some of the energy lost during braking and stores it in the battery. However, this technology is not widely available on electric bikes as it requires a direct-drive motor, which is heavier than the motors typically used in electric bikes.

The best RPM situation in electric bikes is in mid-drive bikes that have enough space to use reduction gears. The mid-drive arrangement does not allow regenerative braking due to the freewheel. The worst RPM situation in electric bikes (lowest RPM) is in hub motors, the only arrangement that would make regenerative braking possible. These hub motors cannot produce high forwards torque and, therefore, cannot produce high inverse torque for braking.

As a result, an electric bicycle with regenerative braking could only produce half of its poor acceleration as braking force, which is not significant. This is in contrast to electric cars, which are well-known for their high acceleration, thus allowing rapid braking.

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