Whist an electric bike and a conventional bicycle shares a number of the same components such as wheels, brakes and chainsets, an e bike  has a number of additional components.

Electric Motor

There are three main motor systems used in e-bikes. These are hub drive motors, mid drive or crank motors and friction drive motors. Its probablty fair to say the most common type is the hub motor due to its low costs and simplicity and the fact it be be retro fitted to a conventional bike.

Click here for a  more detailed description of e bike motors.

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Battery

The battery is often the most expensive part of an e-bike. They are often fitted to the downtube or into a rear rack. With the introduction of smaller and more efficient brushless motors batteries are increasingly being fitted inside the frame.

In the early days of e-bikes Nickel Cadium cells were often used but in modern e-bikes lithium-ion technology is used in the form of 18650 or the slightly larger 21700 cells. These are lightweight, high capacity, safe and long lasting with the ability of being charged hundreds or even thousands of times. Its better to use cells from companies such as Samusung, Panasonic, LG rather than generic cells.

The number of cells in the battery and wiring configuration (banks of cells in parallel connected in series) determine  the voltage and capacity of the battery pack. Most e-bike packs are 36v or 48v but they can go as low as 24v or as high as 72v.

The battery will also contain a Battery Management System (BMS) which controls the balanced charging of the pack to prevents overcharging or overdischarging.

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Speed Controller

This part is rarely visible on an e-bike but is an essential component. It has two main functions. It converts the DC power from the battery into AC for the brushless motor. It also regulates the voltage to the motor and hence the speed.

 

Throttle

Whilst not legal in the UK some e-bikes are fitted with throttles which may be either on a thumb switch or and twist grip.

 

Pedal Assist System / Torque Sensor

Most e-bikes will have a Pedal Assist System (PAS) or a torque sensor. Both these control the motor if the rider pedals but there is a big difference between the two.

A PAS tells the speed controller that the user is pedaling and so activates the motor according to the speed setting on the display control unit. A torque sensor not only measures pedaling but also the effort that the rider is putting in and then boosts the motor power according to the setting on the display control unit.

 

Display Unit 

Many e-bike have some sort or LCD / LED display unit mounted on the handle bars. This usually allows the rider to see information such as speed, battery range, battery capacity, trip distance, power setting etc. It also allows the rider to change the power level of the motor and other features such as walk mode.

Some modern bikes do not have a display unit but instead have a simple switch allowing the user to control the power level and a series of LED’s. More advanced functions can be controlled using an app on a phone which is connected to the bike via Bluetooth.

Unfortunatley there is very little standardisation and control unit only generally work with certain motor / battery combinations.

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