E-Bike and Electronics Glossary: Motor, Battery, Wh and Sensors

A bike with a motor that helps you pedal. In the European Union, to count as a regular bicycle, the motor can't exceed 250 W rated power and must stop assisting at 25 km/h (15.5 mph). Most US states use three classes instead: Class 1 and 2 assist up to 20 mph and Class 3 up to 28 mph.

See also: EPAC, speed pedelec, mid-drive motor, battery E-Bike Range

Short for Electrically Power Assisted Cycle, the technical name for an e-bike in the European standard EN 15194: assist only while pedaling, up to 25 km/h (15.5 mph) and 250 W rated power.

See also: e-bike, assist cut-off speed, rated power E-Bike Range

An e-bike that assists up to 45 km/h (28 mph). In Europe it's legally a moped: it needs type approval, a license plate, insurance, an approved helmet and a driver's license.

See also: e-bike, assist cut-off speed

A motor mounted at the bottom bracket that drives the cranks. It makes use of the bike's gears and keeps the weight centered; it's the norm on e-MTBs and mid- to high-end e-bikes.

See also: hub motor, torque, torque sensor E-Bike Range

A motor built into the front or rear wheel hub. It's cheaper and quieter, but doesn't use the bike's gears and throws off the weight balance.

See also: mid-drive motor, hub E-Bike Range

The lithium-ion pack that powers the motor. Its capacity is measured in watt-hours: 400 to 500 Wh on many city e-bikes and 600 to 800 Wh on e-MTBs.

See also: watt-hours (Wh), range, lithium-ion, charger E-Bike Range

The unit of energy stored in the battery: volts times amp-hours. A 36 V, 14 Ah battery holds 504 Wh; at 16 Wh per mile (10 Wh per km), that's about 31 miles (50 km).

See also: battery, range E-Bike Range

How far you can ride on one charge. It depends on the battery, assist mode, climbing, weight and temperature: the same battery can last three times as long in the lowest mode as in the highest.

See also: watt-hours (Wh), assist modes, range extender E-Bike Range

The turning force the motor delivers, in newton-meters (N·m). Full-power e-MTB motors put out 85 to 120 N·m (the current Bosch Performance Line CX reaches 120 N·m) and lightweight ones 35-60 N·m. You feel it most when starting off and on steep pitches.

See also: mid-drive motor, torque sensor E-Bike Range

A sensor that measures how hard you push on the pedals so the motor helps in proportion. It feels natural: the harder you push, the more the motor gives.

See also: cadence sensor, torque, assist modes

A sensor that detects whether the cranks are turning and how fast. On basic e-bikes it switches the motor on whenever you pedal, without measuring force; in training it measures pedal revolutions per minute.

See also: torque sensor, cadence, ANT+

The motor's levels of help (Eco, Tour, Turbo and similar). Each one multiplies your effort by a different amount; automatic modes adjust it on their own based on how you pedal.

See also: range, torque sensor, display E-Bike Range

A feature that moves the bike at walking pace, up to 6 km/h (3.7 mph), while you push it. Handy on unrideable ramps or for getting the bike up a steep driveway.

See also: assist modes

The speed at which the motor stops helping: 25 km/h (15.5 mph) on an EPAC and 45 km/h (28 mph) on a speed pedelec; 20 or 28 mph on US Class 1-3 e-bikes. Above it, it's all your legs.

See also: EPAC, speed pedelec, speed sensor E-Bike Range

The power the motor can deliver continuously, limited to 250 W on an EPAC (US federal law allows up to 750 W). In short bursts it delivers much more, sometimes 600 W or more, without breaking the rules.

See also: EPAC, torque

The chemistry of almost every e-bike battery. To make it last, store it at 30 to 60% charge in a cool, dry place, and avoid charging it below freezing or in direct sun.

See also: battery, charge cycles

The number of full charges a battery can take before it loses noticeable capacity; manufacturers usually quote 500 to 1,000. Two half charges count as one cycle.

See also: battery, lithium-ion, charger

The device that charges the battery from a wall outlet. A 4 A charger fills a 500 Wh battery in about 4 to 5 hours; fast chargers, at 6 to 8 A, take much less.

See also: battery, charge cycles

A small extra battery, about 160 to 250 Wh, that mounts in the bottle cage to extend range, especially on lightweight e-bikes.

See also: range, battery, bottle cage E-Bike Range

An electric mountain bike, almost always with a mid-drive motor and full suspension. Lightweight (SL) models use smaller motors and batteries to weigh several pounds less.

See also: mid-drive motor, full suspension

A bike built to carry heavy loads or kids, with a front box (long john) or a stretched rear end (longtail). Most are electric and handle 330-550 lb (150-250 kg) of total weight.

See also: e-bike, rear rack

The handlebar unit on an e-bike that shows battery level, mode and speed, and lets you change modes. Some e-bikes replace it with a remote with indicator lights and a phone app.

See also: assist modes, bike computer

A derailleur moved by a small motor when it gets a signal from the shifter, either by wire (Shimano Di2) or wirelessly (SRAM AXS). It shifts the same every time and doesn't go out of adjustment from cable stretch, but you have to charge its battery.

See also: rear derailleur, shifter

A low-power wireless protocol used by sensors (power, heart rate, cadence) and bike computers. It works alongside Bluetooth Low Energy, which is what phones use.

See also: bike computer, power meter, cadence sensor

A sensor on the hub, or a magnet on a spoke, that counts wheel revolutions and, using the circumference, calculates speed and distance. On e-bikes it's what lets the motor cut assist at the legal speed limit.

See also: wheel circumference, assist cut-off speed, bike computer Tire Size

A rear light with radar that detects cars approaching from behind, up to about 460 ft (140 m), and alerts you on your bike computer or phone.

See also: front light, bike computer

A white light required at night by law in most US states and in Spain (where it's also mandatory in tunnels), along with a red light or reflector at the rear. It's measured in lumens: 200-400 is enough in the city, and for unlit paths you'll want more than 800.

See also: bike radar