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Understanding the electric components of an eBike

Understanding the electric components of an eBike

January 17, 2022 | Justin Christopher

EBikes (electric bicycles) look and ride just like traditional bicycles, but add electric motors that propel the rider faster and further than they could go on pedal power alone.

If you're interested in learning more about eBikes, it's important to understand the key electrical components shared by all makes and models. While the specific parts may look slightly different, on all eBikes you will find:

An electric motor

An eBike motor could be placed in the hub at the center of the wheel ("hub motor") or located at the center of the crankarms ("mid-drive").

The electric motor can output more or less power based on decisions being made by the controller, making the eBike go faster or slower, or providing an extra boost for headwinds or hills.

A battery

You might find an external battery on the outside of the bicycle frame, on top of a rear rack, inside a bag on the handlebars, or even stealthily hidden inside the frame.

The vast majority of modern, high-quality eBikes use Lithium Ion batteries. Obsolete technologies like sealed lead-acid batteries provide significantly less lifespan and range.

Batteries come in a variety of capacities (measured in Watt-hours) and you can think of them like the "fuel tank" on an eBike. Batteries with a higher Watt-hour rating have more range.

Each eBike will include a matching battery charger that runs on AC power. Most eBike models support charging the battery while it's installed on the eBike, and also the battery alone, removed from the eBike.

The controller

You can think of the controller as the "brain" of an eBike. It measures the rider's pedaling input, the speed of the bike, battery voltage, and other factors; and uses that information to control the electric motor. The controller turns the motor on and off, and directs the specific power output of the motor as well.

The display

It's worth noting that the controller is NOT the display. Most higher-quality ebikes have a separate display mounted to the handlebar which shows speed, distance, pedal assist level, and other useful metrics. The controller might be hidden inside the frame tubes on some models, on other eBikes, you might find it strapped or bolted to the exterior of one of the frame tubes.

Sensors

The controller on your eBike needs to know when you're pedaling and when you stop. To measure those factors, a cadence or torque sensor is used. Cadence sensors detect movement when the rider pedals, while torque sensors measure pedaling force using a strain gauge, and adjust motor power accordingly.

You'll also find a speed sensor, often in the rear hub, that tells the controller how fast the eBike is traveling at any given time.

A remote, or "Human Machine Interface"

EBikes include an HMI - usually mounted to the handlebars - that allows the rider to control the available features. The HMI remote typically offers up and down buttons for changing the desired level of pedal assist, buttons for powering the bike on and off, and the ability to operate the menus and settings on the display.

A throttle (optional)

Some eBikes include an additional component - a handlebar-mounted throttle, which might come in a motorcycle twist style, or a push button style you push with your thumb. Bikes equipped with throttles (Class II models, and some Class III models) allow you to turn on the electric motor on-demand, propelling the eBike without pedaling at all.