Regenerative Braking in Electric Bikes

March 23, 2021 0 Comments

Electric bikes are considered as alternative transportation for fast travel however, there is always a fear of having a short driving range. To resolve this issue, elaborate research about brake energy recovery technology or regenerative braking is available.

But what is Regenerative braking? To explain it in easy words, one can say that it is the process in which the energy from the motor is used to charge the battery while braking. Regenerative braking is common for electric vehicles, however, it is rare on electric bicycles.

 In electric bikes, the regenerative braking system contains a developed microcontroller-based control system. Regen means that the electric motor is used to slow down the rider when stopping and generating some energy. The energy is then fed back into the battery pack which ultimately increases the efficiency of the rider and range.

Regenerative braking drastically reduces the brake wear and prevents the brakes from getting hot especially while riding down the hills. Moreover, regenerative braking never squeaks and has a smooth feel. Electric bikes that have a gearless hub motor also have regenerative braking.

Further, regenerative braking in electric bikes is seamless in the riding experience. The rider will notice a gentle acceleration from the direct drive motor compared to a bike with a geared hub motor. In simple words, regenerative braking acts like a powerful dynamo when the levers are pulled.

How regenerative braking works?

Regenerative braking is an advanced and supplementary braking system. Before regenerative braking, there was friction between brake pads and brake discs. Thus, converting the vehicle’s kinetic energy into heat which is wasted and dissipated into the air. Howbeit, regenerative braking utilizes this waste energy by charging the e-bike battery.

The regenerative system works with dual functions. It acts as a motor in one direction while as a generator in the opposite direction. As a motor, it converts the kinetic energy into mechanical energy by driving the wheels. However, while braking the system acts as a generator, running in the opposite direction.

Regenerative braking captures the rider’s kinetic energy as soon as he applies the brakes. The energy is then put back into the battery to use instead of wasting it on a stop. Nearly all the energy from the battery is utilized in combating air resistance.

Since the rider weighs lesser than a car. Thereby, there is a huge amount of energy available to be captured. While cycling almost 90% of the rider’s effort and energy is exerted opposing the air. The air resists as the riders move forward. Thus, the cyclist can only go 10% further. As the rider captures all the kinetic energy while braking.

Regenerative brakes on electric bikes create extra drag, even when not using the brake. Since the motor is always engaged in an e-bike with a regen system, so the motor is always turning even when coasting. The positive effect on the efficiency of a regenerative system greatly outweighs the small negative effect created by the extra drag.

When the battery of e-bikes is full, power will not flow into the battery. This phenomenon helps in protecting the battery. It also ensures that whether regenerative braking is converting more energy to the battery than it can handle or not. Also, if the brake levers are too tight. There may be a chance that the mechanical brakes begin to stop the bike before regenerative braking has a chance to kick in.

Anyhow, regenerative is effective only up to certain speeds. It is not very efficient at lower speeds. So, it only effectively assists the regular braking. The braking duties are not entrusted to the regenerative braking alone. Also, even in ideal conditions, there will only be a 10% recharge back to the e-bike battery. This is because braking periods are short and batteries like to be charged at low currents for a long time.

Why don’t E-bikes use Regenerative Braking?

Firstly, regenerative braking requires a far more complex interconnected braking, battery, and drive system than what you typically have with a normal e-bike. The design is complex and significantly drives up the cost of manufacturing the e-bike. The cost of all the features of e-bike would get put onto the consumer until the company itself cuts down on quality in other components. The price alone is often a huge turn-off for most e-bike companies.

Secondly, regenerative braking is a much heavier braking system than a typical e-bike brake system. The added weight means that the overall performance, especially the range, is going to be impacted. While regenerative braking typically adds 10% to 15% of range back to the battery as the rider rides. The added weight will also lose 2% to 5% of the range. As a result, the overall range extension is quite small compared to the price you must pay for it.

Thirdly, regenerative braking is detrimental once the battery of the e-bike is dead. As the added weight and complex motor system, the regenerative braking system impacts how hard the rider must pedal to accelerate with your e-bike. Most e-bikes will provide a normal pedaling experience with their motor on or off, but that is not the case with regenerative braking systems.

Lastly, this braking system causes the battery of e-bikes to degrade faster. The batteries of electric bikes have a certain number of charging cycles. It varies with the type and company of the battery used. Each time the battery is charged, it loses a fraction of its total capacity. Therefore, the battery needs to be replaced after a few years. Regenerative braking causes degradation. The degradation caused by regenerative braking is far less effective than the power boost provided by a dedicated charger.

Furthermore, regenerative braking does a special job. It converts kinetic energy to electricity, but in the process of doing so will create its heat as well. Due to their proximity, the batteries will be exposed to more heat than they otherwise would be with a traditional braking system. This can also cause the battery to degrade more quickly.

Hope this article has helped you in understanding the concept of Regenerative braking better. For any further queries feel free to get in touch with us in the comments below.

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