An electric bike that recharges when you pedal is commonly known as a regenerative electric bike or a regenerative braking electric bike. These bikes use a special feature called regenerative braking that allows the bike's motor to convert the kinetic energy generated by the rider's pedaling and braking into electrical energy, which is then stored in the battery.

When the rider applies the brakes, the regenerative braking system kicks in and the motor acts as a generator, converting the kinetic energy generated by the bike's motion into electrical energy. This energy is then stored in the battery, which can then be used to power the bike's motor when needed.

While regenerative braking can help to extend the range of an electric bike by recharging the battery while riding, the amount of energy that can be generated is typically quite small compared to the energy needed to power the bike's motor. As such, regenerative braking is best seen as a way to supplement the battery's charge, rather than a primary means of recharging the battery.

It's worth noting that not all electric bikes are equipped with regenerative braking systems, and those that do have them may not be able to generate enough energy to make a significant impact on the bike's range. If you're interested in a regenerative electric bike, it's important to do your research and choose a model that offers a reliable and effective regenerative braking system.