How do electric bikes work? Battery, motor, sensors and controls

The five extra parts on an electric bike

An electric bike is a bicycle first. It has a frame, wheels, pedals, a chain and brakes like any other bike. On top of that come five parts that work as one system:

• Battery: stores the energy.
• Controller: the small computer that decides how much power goes to the motor.
• Motor: turns electric power into a push.
• Sensor: tells the controller when, and on some bikes how hard, you pedal.
• Display and controls: where you switch on, pick an assist level and see speed and charge.

Every ride runs the same loop. You pedal, the sensor reports it, the controller reads the assist level you chose, and the motor adds a matching push. Stop pedaling or pull a brake lever and the motor backs off.

The battery: where the energy lives

Most e-bike batteries are lithium-ion packs made of many small cells, managed by a battery management system that guards against overcharging and overheating. Two numbers describe them: voltage (V), which is the electrical pressure, and amp hours (Ah), the capacity. Multiply them for watt hours (Wh), the total energy.

The Speedway Riders Q3, for example, carries a removable 48V 20Ah battery listed at 960Wh, and the Hiboy EX11 a removable 48V 18Ah pack at 864Wh. More watt hours means more range and more weight. Our guide to electric bike battery range explains how those figures turn into miles, and our sibling guide to electric bike battery care covers charging and storage.

The controller: the brain of the bike

The controller sits between the battery and the motor and decides how much current to send. It reads the sensor, the throttle, the assist level and the brake levers many times a second, and sets the motor’s output to match.

The controller is also where the speed limit lives. When the bike reaches the top assisted speed for its class, the controller stops sending power. That is why a switchable class bike, like the Segway Myon, can follow class 1, 2 or 3 rules from a setting rather than new parts. Some listings name the controller: ASAP lists a 48V 22A controller for the ASAP Varna.

The motor: where the push comes from

The motor sits either in a wheel hub or between the pedals. A hub motor turns the wheel directly. A mid-drive motor turns the chain, so it works through the bike’s gears. Our guide to hub vs mid drive motors compares them in full.

Within hub motors there are two common types. A geared hub, like the 500W unit on the ASAP Zen, uses small internal gears to give more pull from a compact motor. A direct-drive hub, like the 750W motor on the Segway MUXI, has no internal gears.

Motor power comes as rated and peak figures. The rated figure is what the motor can keep up; the peak is a short burst. The AOTOS FLUX X26 shows the difference clearly: a 750W rated motor, with Boost mode reaching 1,200 W on the X26 and 2,000 W on the X26 Pro, for up to 10 seconds at a time. Torque, listed in Nm, tells you how hard the motor pulls from a stop and up a hill: the Hiboy EX11 lists 90 N·m.

Pedal sensors and the throttle

The sensor is what makes an e-bike feel like a bike. There are two main kinds:

• Cadence sensor. It detects that the pedals are turning and switches the motor on at a set level for each assist setting. The Segway MUXI lists a cadence sensor.
• Torque sensor. It measures how hard you press on the pedals and scales the motor’s help to your effort. The Hiboy EX11 and the Segway Myon list torque sensors, and the Hiboy EX9 a dual-sided one.

Some bikes offer both: ASAP lists torque or cadence sensing for the Varna and the Zen. Our guide to torque vs cadence sensors explains how each one feels.

A throttle sends power without any pedaling, from a thumb lever or twist grip. Under the class system it belongs to class 2 and stops helping at 20 mph. Our guide to throttle vs pedal assist covers when each mode makes sense and how each one affects range.

The display, assist levels and riding modes

The display is your control panel. It switches the system on, shows speed and battery charge, and lets you pick an assist level. Low levels add a gentle push and save battery; high levels add more help and use it faster. The Segway Xafari lists 12 levels of pedal assist, and the Q3 lists an LCD that shows speed, mileage and battery.

Many bikes also offer riding modes. Hiboy lists bike, power assisted and pure electric modes on the EX9, so you can ride with no motor, with pedal assist or on the throttle alone. With the motor off, an e-bike rides like a heavy regular bicycle.

Brakes, gears and the rest of the bike

Most e-bikes have brake levers with a motor cut-off. Pull a lever and the controller stops the motor, so it never pushes against your brakes. Hiboy lists power off brakes on the EX9, and the Hiboy C1 lists a motor cut-off on its front and rear disc brakes. Our sibling guide to electric bike brakes compares hydraulic and mechanical discs.

Gears still matter on an e-bike, especially with pedal assist. The Q3 uses a Shimano 7-speed drivetrain, and Segway lists 9-speed electronic auto shifting on the Segway MUXI Pro, which shifts for you as you ride.

Maker figures, checked September 2026. Real range and speed depend on rider weight, terrain, temperature and riding mode.

Keeping the system healthy

• Power off before you clean or adjust anything, and follow the maker’s manual.
• Keep water away from connectors. Check the listed water rating: the Q3 lists IPX4, and the Hiboy EX11 lists IP65 for its battery and motor.
• Charge with the supplied charger, on a hard surface, away from anything that burns.
• Leave battery, controller and wiring work to a qualified technician. Never try to raise a speed limit or modify a battery.
• Check our warranty page if a part fails under normal use.

Our electric bike maintenance checklist covers the rest. Ready to choose? Start with how to choose an electric bike, then browse our electric bike shop. Every order ships free to the lower 48 states.

Questions riders ask