Do electric bikes charge when pedaling? The short answer is most do not, but there are a few electric bikes available that do have regenerative capabilities. Bike manufacturer that offers regenerative equipped e-bikes will on average charge your battery less then 10%, and if you are really careful and break lightly when coming up to stoplights and going down hills, you may be able to get a regenerative charge as high as 20% but most likely lower.
What many people think when they first hear about e-bikes is that an electric bike will charge itself when pedaling. This is true in some ways with some regenerative electric bikes sold today, but because of the low 10% return on input, a person would need to pedal 10 miles to give them a 1-mile charge.
For this reason, it is still better to use a charger and plug into a wall outlet. Most e-bike batteries take around 4 hours to charge and cost approximately 20 cents with a range of from 30 to 50 miles if you put that into perspective with a regenerative electric bike you would have to pedal for 100 miles to get 10 miles back.
What is regenerative braking?
Regenerative braking is when an electric bike uses its braking system and motor to recapture some of the bikes kinetic energy and convert it into electricity, and this energy is used to charge the e-bike's battery. With a typical braking system, the brakes are applied, and this will create friction, this friction will then slow or stop your bike.
The surface of the road and the surface of the slowing wheel also produces friction. This friction generates kinetic energy, and this energy is dissipated into the air. In short, this heat energy is wasted. Regenerative power captures some of this energy but is not very efficient. A regenerative electric bike uses the motor to slow the bike down.
When the rider squeezes the brakes, the controller puts the bikes electric motor into reverse mode, causing the motor to run backward and slow the bike down.
When the motor is running backward, this turns the motor into an electrical generator and produces electricity that can be fed back to the battery. The controller will decide when the motor should be reversed, and send back electrical energy to charge the battery.
In a regenerative braking system, the idea is to get the motor to run backward and to use the momentum of the mechanical energy to puts the motor into reverse.
Momentum is the property that keeps the electric bike moving forward once it has been brought up to the desired speed. When the motor is reversed, the electricity generated by the motor is then fed back into the battery, where it can be used to accelerate and move the bike forward after the bike has stopped.
A person will use more caloric energy than the electrical energy produced.
In theory, you can completely recharge a battery by pedaling and keeping the brakes on lightly, but in reality, it is not too efficient. For a person to completely recharge a battery, a person would have to pedal for the entire day.
A human pedaling for several hours with the added resistance of the brakes will burn up many calories and have to consume a lot of food to charge the battery. What you are doing is converting leg energy ( mechanical energy) into chemical energy that is then stored in the battery.
If you remember from science class that calories are a form of energy. The calories used will provide much less electrical power than the energy required to produce it, this makes regenerating a battery not very efficient.
Effectiveness of regenerative braking systems on an E-bike
The effectiveness of a regenerative electric bike can vary significantly based on many factors like driving conditions, terrain and the size of the rider. Driving conditions can make a big difference in the effectiveness of regenerative brakes.
If you ride in stop and go traffic and repeatedly brake, you will capture much more energy than you would if you rode on a long flat stretch without stopping or using the brakes.
If you do a lot of uphill riding, you will not use the brakes very often and have less opportunity to generate electricity.
Motor torque variations cause another issue for regenerative braking. Drivers tend to vary the amount of braking. For example, a driver might increase their pressure on the brake as they slow down. This variation in torque causes inefficiencies since the regenerative braking must take into account the variations in torque as it calculates the amount of energy to recoup.
The benefits of a regenerative braking system
Brakes last longer on an Electric regenerative bike. Another advantage of regenerative brakes is not only are you by using the motor to slow your bike and producing electricity you are using the brakes pads much less and thereby your breaks will last much longer. Compared to regular breaks.
Problem with a regenerative braking system
One problem with regenerative braking systems is they are not the best for two-wheel-drive braking systems. A negative torque is applied to the drive wheel when the regenerative braking system is used. This negative torque is applied to only one wheel, and no brake is applied to the other wheel, and it is able to spin freely.
You will get uneven tire and brake wear because of negative torque distribution. This could cause skidding when braking. This is why most e-bikes with regenerative systems have a rear hub motor as opposed to front hub motors that could be much more dangerous.
The motors torque variations cause other issues for regenerative braking systems. Drivers often vary the amount of braking they do in different driving conditions. A driver might increase their pressure on the brake as they slow down.
A regenerative braking system must take into account the changes in torque to calculates the amount of energy to recoup. These variations in torque cause further inefficiencies in regenerative braking systems.
So do electric bikes charge when pedaling?
So there you have. In theory, it would be nice if you could pedal and charge your battery and go forever, but reality and science do not make this true. A few manufacturers are offering regenerative electric bikes, but they come at a premium price.
When using a charger and plugging into an AC outlet, it will cost less than ten cents to charge an e-bike battery fully. Whereas to pedal all day to charge a battery you will burn thousands of calories and that caloric energy will have to be replaced with food and that food you will need to consume will cost much more than 20 cents.
With the ever-increasing move toward electric vehicles. I think they will be working to improve the efficiency of regenerative technology, but in the meantime, you will only get about 10% back for your efforts.
