E-Bike Glossary
Spec sheets love jargon. Here's what the terms actually mean, in plain garage language, so you know exactly what you're buying.
A
Amp-hour (Ah)
How much charge a battery holds. Multiply by voltage to get watt-hours: a 48V 14Ah pack is 672 Wh. Ah alone tells you nothing without the voltage.
B
Battery Management System (BMS)
The circuit board inside the pack that keeps cells balanced, cuts power when voltage gets too low or high, and protects against overheating. The unsung hero of pack longevity.
C
Cadence Sensor
A pedal-assist sensor that only detects THAT you are pedaling, not how hard. Cheaper, but assist feels on/off compared to a torque sensor.
Class 1 / 2 / 3
The US legal framework. Class 1: pedal assist only, 20 mph cap. Class 2: adds a throttle, 20 mph. Class 3: pedal assist to 28 mph, usually no throttle. Trail and state rules vary.
Controller
The box that takes battery power and feeds it to the motor based on your input. Its amp rating, with battery voltage, sets the real power ceiling of the bike.
H
Hub Motor
A motor built into the wheel hub (usually rear). Simple, cheap, low maintenance — but heavier at the wheel and less efficient on steep climbs than a mid-drive.
M
Mid-Drive Motor
A motor at the cranks that drives through the chain and gears. Climbs better, centers the weight, feels natural — but costs more and wears drivetrain parts faster.
N
Newton-meter (Nm)
The unit of motor torque. More Nm means stronger acceleration and hill climbing. Commuter hub motors run 40-60 Nm; strong mid-drives 70-100 Nm.
P
Pedal Assist (PAS)
The system that adds motor power while you pedal, usually in selectable levels. Higher levels eat more watt-hours per mile — which is why range claims vary so wildly.
T
Throttle
A lever or twist grip that powers the motor without pedaling. Standard on Class 2 bikes. Convenient, but the fastest way to drain a battery.
Torque Sensor
A pedal-assist sensor that measures how hard you push and scales motor power to match. Smoother and more efficient than a cadence sensor; found on better bikes.
W
Watt-hour (Wh)
The honest measure of battery size: voltage times amp-hours. Divide Wh by your Wh-per-mile consumption to estimate real range. The single most useful spec on the sheet.
Important Disclaimer
These definitions are simplified for educational purposes. Always consult with professionals for technical specifications.