Conversion kit for Electric bicycle : 26" Rear Wheel 48V 500W
To drive a large diameter bicycle wheel requires high torque, but modest RPM. A gear-reduced motor has many advantages compared to a direct-drive of equal power: it weighs less, it can produce much greater torque, and will consume less current from the battery at low speed. All of these advantages are offset by it’s single major disadvantage: mechanical complexity and reliability.
Driven by a 12 Fet, 25A controller, the motor is capable of exerting 74Nm (54.5 foot pounds) of torque at a stall, more than twice the torque of a 500W direct drive motor. This means you can climb much steeper hills and carry much heavier loads. As a comparison to achieve such torque, a direct drive motor would weigh at least 8.0kg and needs to be powered by 48V controller with minimum 35A current.
The lack of regen braking is cited by some direct-drive vendors as a disadvantage of gear-reduced motors. While the freewheel bearing does make regenerative braking impossible, the wasted braking wattage is more than offset by the more efficient acceleration.
It has taken over 10 years to source a gear-reduced motor that will withstand the gear-crunching forces it must endure, but since 2012 Motorino has relied on the Bafang line of gear reduced motors and cover them with two years warranty.