How Motors Work With the Rest of the E-Bike
In addition to the motor, all e-bikes have motor controllers and batteries. The controllers modulate the amount of power flowing to the motor, which uses your input to transfer the desired amount of current from the battery into the motor.
“What makes an e-bike an e-bike is the experience of how power is being doled out,” Lemire-Elmore says. Pedal-assisted e-bikes might use a speed (a.k.a. cadence) sensor, which regulates e-assist by detecting the rider’s pedaling cadence, or torque sensors, which sense how much torque the rider is putting into the pedals.
Some e-bikes have throttles that allow you to use the motor independent of your pedaling, although regional laws define where you can and cannot use throttle-equipped e-bikes.
The Different Types of Motors
Despite sharing the same basic tech, the motors you’ll see on today’s e-bikes come in three basic variants. Mid-drive motors are positioned at the center of the bike’s frame, where you’d normally find the bottom bracket.
Hub-driven e-bikes have motors within the front or rear hub, and there are two types of hub motors. Direct-drive hub motors, apart from their bearings, have no moving parts: The motor just spins around the axle, which is secured to the frame’s dropout.
Geared hub motors use a series of planetary gears to lower the motor’s RPM and increase its torque output. You’ll also find aftermarket e-bike kits that allow you to equip a standard bike with a mid-drive or hub motor, and among aftermarket kits, there are friction drives, which use a spinning wheel that contacts the rear tire to create propulsion.