How Does an Electric Bike Motor Work? - ElectricVehiclesFAQs.com

Revamping traditional bicycles through the integration of electric motors has proved to be one of the greatest ideas in the world of vehicles.

The mechanism of an electric bike motor is simple: You turn on the motor through the given switch. The motor takes power from the battery and comes into action by producing torque, the power which makes things spin. The motor’s torque moves the drive shaft that, in turn, operates the chain ring.

How does the motor of an electric bike work? It depends upon numerous factors. Let’s look at them in detail.

Table of Contents

1. Components of an Electric Motor

Motors work on the principle of electromagnetism. But how? Well, it’s a very simple process.

A magnetic field is created when you take a wire, coil it around a rod, and pass electricity through it. The magnetic field has two poles, North and South. When you surround that rod with several magnets, the attractive and repulsive forces of the poles make it spin in a single direction.

To understand how the motor of an electric bike works, you need to know what it’s made up of. The basic components of the motor of an electric bike are:

a) Stator

This is the outer, fixed component of the motor consisting of 3 parts: outer frame, core, and permanent magnets.

First comes the outer frame that supports the stator’s core. Then comes its hollow cylindrical core made up of high-grade silicon steel laminations. It protects the stator’s inner windings. Finally, the permanent magnets create a stationary magnetic field around the rotor.

b) Rotor

This is the moving component of a motor located on an axis inside the stator. It contains two parts: core and windings.

When current passes through the rotor’s windings, they generate a rotating magnetic field. The stator’s fixed magnetic field attracts and repels the rotating magnetic field of the rotor. This interaction creates a torque, making the rotor spin on its axis.

Also read, Advantages and Disadvantages of Electric Bikes

c) Commutator & Brushes

If the rotor windings are directly connected to an external power source, they would twist and break off. Therefore, the current is carried to the rotor windings through the combination of brush and commutator.

Brushes, now made of carbon instead of copper, are the electrical conductors that ride along the commutator to carry the current between stationary wires and moving parts.
A commutator is a mechanical rotary switch located on the rotating shaft. It comprises of split rings segments, each connected to the windings on the rotor. These rings receive the current from contact with the brushes and reverse the current direction before supplying it to the rotor’s windings

*Note: The reversal of current is necessary with each half turn to maintain a full rotation. The torque produced on the rotor would not work in the same direction otherwise.*

Read How Do You Charge an Electric Bike

2. Type of motor

The motor of an electric bike works according to its internal design and placement on the bike. Let’s see how they are classified into different kinds.

a. Design

Based on their internal design, there are two basic electric bike motors: Brushed DC and Brushless DC. Brushed DC motors are rarely used in electric bikes now because they are not as efficient as brushless motors.

Brushed DC Motors

This is the simplest kind of motor that has been in use for a long time now. You can usually find it in many common electrical devices, including blenders, power drills, and other home appliances.

As evident by the name, carbon brushes play a critical role in the working of a brushed DC motor. These brushes make sliding contact with each commutator segment as it rotates, producing an electrical charge.

Characteristic	Detail
Design	The stator of a brushed motor contains permanent magnets, while the coil windings are attached to the rotor. The motor works when the electric charge reaches the rotor through the brushes and the commutator.
Complexity	The design of a brushed motor is simple. This is why they are more commonly known and understood than brushless motors.
Cost	Brushed motors are not that expensive because they contain fewer parts than brushless motors.
Efficiency	The need for regular maintenance of brushes and commutator makes these motors a less-efficient option. Therefore, they are rarely used in electric bikes now.
Lifespan	The friction caused by the sliding contact between the brush and the commutator wears down the brushes over time, reducing the motor’s life.
Noise Generation	The brushes sliding against the commutator produce a lot of mechanical or electromagnetic noise.

Brushless Motors

They are a more efficient replacement for brushed motors. There are no mechanical brushes or commutators involved. Instead, sensors are used to control a brushless motor.

Sensors take signals back and forth from the control unit in the form of currents to control the motor’s rotation. Simply put, commutation in a brushless motor happens electronically through a complex control unit.

Characteristics	Detail
Design	The design of a brushless motor is just the opposite of a brushed motor. The stator of a brushless motor contains the coil windings, while the rotor is mounted with the permanent magnet. Instead of a brush and commutator, an electronic controller drives the rotor.
Complexity	A brushless motor requires more complex equipment like a computer, controller software, controller, wiring/cabling, and encoders.
Cost	Brushless motors come with an expensive controlling system. Hence, they cost more than the brushed motors.
Efficiency	No physical contact between any motor parts means less wear and tear possibilities. Plus, these motors are known to accommodate higher speed ranges than its counterpart.
Life span	Brushless motors last longer than brushed ones as there are no parts to wear out.
Noise Generation	The parts of a brushless motor are electronically controlled, so there is no mechanical or electromagnetic noise involved.

b. Placement

The motor of an electric bike can be placed in the following areas: front-hub, rear-hub, and mid-drive. Each placement comes with its own pros and cons. Let’s discuss them in detail below.

Read How Much Does an Electric Bike Battery Cost?

Mid-Drive

You can find mid-drive motors in the middle-bottom of the bike near the cranks (the part that connects the bottom bracket and the pedals). Here are some features worth considering.

The power travels from the motor to the rear wheel through the drivetrain and pushes the vehicle forward. The motor only complements your drivetrain instead of adding any additional power. This means that the harder you pedal, the more power the motor applies.
Mid-drive motors work the best for mountain and off-road bikes. They utilize the bike’s geared drivetrain for smooth low-speed climbing. Plus, their middle placement evens the weight distribution on the bike, ensuring higher stability. Their lower sprung weight also helps in steep climbs.
Although mid-drive motors are available in different sizes and weights, they make the bike look bulky in general. Also, they can cause the chain and shifters to wear out quickly. Plus, placing the motor in the middle makes the bike noisier.

Read How Many Calories Do You Burn on an Electric Bike?

Hub-Drive

Hub refers to the central part of a bike’s wheels. You can place the motor of an electric bike in the front tire or the rear wheel to build a direct connection with the ground. Let’s look at some noticeable traits of this placement.

Hub-drive motors are more common than mid-drive ones because manufacturers don’t need to alter to the frame of bikes to fit these motors. Plus, bikes with hub motors require less maintenance than mid-drive ones because they don’t stress the chain ring.

However, changing tires on an e-bike with hub motors is more difficult because the motor is fixed on the wheel. Plus, they have a fixed gear ratio, making it more challenging to climb steep hills.

Hub motors can be further classified into two kinds: Front-hub and rear-hub.

Front-hub Motors

Do you know most of the gear and batteries are installed in the middle or rear of the bike? The front of a bike usually holds the least weight. Therefore, placing your motor in the front wheel can spread the weight of your e-bike even better than the mid-drive motors.

Moreover, front-hub motors are the most affordable option, considering power rating and simplicity. You can easily get offerings of 250–350W, involving fewer magnets and less copper wire.

Plus, front-hub electric bike motors are easier to install than rear-hub motors. There is no need to worry about transferring over the freewheel or adjusting your derailleur.

However, they offer the least torque and power compared to other motors. The front part of the bike already doesn’t weigh enough. Driving the front wheel by motor, rather than the rear wheel, can produce a push-pull feeling that affects your balance. Therefore, front hub motors are best suited for casual pavement rides.

Read 500-Watt Electric Bike or 750-Watt Electric Bike

Rear-hub Motors

Rear-hub motors provide the most traction because your body weight is mostly supported by the rear wheel. Therefore, they work the best on dirt roads where you need a strong grip.

However, you might need to change rear tires more frequently than the front wheels. Why? Because any sharp object lying flat on the ground does not harm the front tire. But once the front tires kicks up that object, it can align with your rear tire and puncture it. Fixing the motor on the rear-hub makes it difficult to change tires so frequently.

Check How Long Does an Electric Bike Battery Last?

3. Level of Assistance

“How does an electric bike motor work?” largely depends on the level of assistance you require. The level of assistance you choose determines how fast the motor will propel you. In the USA, the motor of an electric bike provides the following levels of assistance: pedal-only, pedal-assist, and throttle.

a. Throttle

Are you too tired to pedal? Want to enjoy a free ride? Well, this is your go-to option then!

Electric bike motor on throttle mode extends all of its power, so you don’t need to pedal. It gives you a similar experience to riding a motorcycle. Different types of throttle include twist grip, thumb, and push button.

b. Pedal-Assist

This is the most commonly used mode of an e-bike.

On pedal-assist mode, an electric bike motor provides the amount of power in correlation to your pedal efforts. Torque and cadence sensors guide the motor regarding the level of assistance you need.

With torque sensors, your bike increases or decreases the level of assistance based on your actual pedal power.
With cadence sensors, the level of assistance remains the same as you select, no matter how hard you pedal.

c. Pedal-Only Mode

This mode makes your e-bike work just like any regular bike. You can turn this mode on when you are in the mood to exercise.

Read Can you take an Electric Bike on Eurostar?

Final Words

Electric bikes provide a clean and efficient way of commuting. They don’t pollute the environment like the combustion engines of other vehicles. Plus, they don’t tire out the rider quickly like those regular bicycles. Before buying one, it’s best to learn about how they work.

So, how does an electric bike motor work? Well, motors are the heart of e-bikes. Their performance is largely based on their design, placement, and modes of control. You will come across a large variety of electric bike motors, including brushed and brushless motors, mid-drive motors, front-hub motors, rear-hub motors, etc.

Each kind of motor comes with its own advantages and disadvantages. You cannot say that one is better than the other. It all depends on how you plan to use your bike. A front-hub motor is a good choice if you want an electric bike for your daily commute. If you want to climb hills, you should select an e-bike with a mid-drive motor. Experience this fascinating technology if you still haven’t!