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How electric bikes work: a basic guide

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How electric bikes work: a basic guide

The electric bicycle is an incredible invention and became popular in the 1990s. They are a complex combination of mechanical and electrical engineering. Although you don’t need to understand every aspect of how electric bicycles work, it’s a good idea to understand some of the basic principles behind electric bicycles if you own an electric bicycle or are considering buying an electric bicycle.


The working principle of electric bicycles is very similar to that of ordinary bicycles. However, electric bicycles have electronic components, motors, and batteries to help the rider move forward. Electricity can help riders manage hillsides and wind and ride farther and farther (without fatigue).


This article will detail how an electric bicycle can be used as both a mechanical vehicle and an electric machine.

Basic knowledge of the working principle of electric bicycles

Electric bicycles use electrical energy to move the bicycle forward, whether it is entirely on your own or with the help of a rider. Electric bicycles have the same structure as ordinary bicycles, but they also have batteries and motors.


I will explain the details of each component of the electric bike in more detail below, but here are some basics.

Electric bicycles are bicycles first

Since electric bicycles can also be used as ordinary bicycles, the following is the basic knowledge about how your electric bicycle moves.


When you step on the pedal, the rotary motion turns a set of gears, called cranks, which are connected to the chain. The chain is also connected to a set of gears in the middle of the rear wheel.


When the crank turns and moves the chain, the chain will rotate the gear on the rear wheel. As these gears are connected to the rear wheels, the wheels will also start to rotate, pushing the bicycle forward.

How does the motor help the electric bicycle move?

Electric bicycles can move in one of three ways.

Unassisted pedaling
Boost pedaling
Use accelerator instead of pedal
You can choose to ride an electric bicycle without a battery or motor, and use it as a normal bicycle, as described above. This can be achieved by not turning on the battery at all or setting the pedal assist gear to “off” or “0” level assist.


It is not recommended to do this on any slope, because electric bicycles are naturally much heavier than ordinary bicycles, which makes them more difficult to ride. However, if you are going downhill or riding on a fairly flat road, you may want to do this in order to do more exercise or to save battery power. In addition, with this option, even if the battery runs out, you can still go home because you can pedal like a normal bicycle.


The most common way to move an electric bicycle is to step on the pedal while turning on the power. For most motors, the pedaling action uses the power in the motor, so you don’t have to actively turn on power assist. The motor facilitates the rotation of the chain or wheel, making it easier to ride a bicycle.


Generally, you can cycle through multiple settings to change the amount of assistance provided by the motor. Some people prefer to use minimal help to save battery and increase exercise. Others prefer to use maximum assistance to make riding easier and more enjoyable.


The last way to move an electric bicycle is the throttle. This means you don’t have to step on the bicycle, just twist the throttle on the handlebar to move the bicycle forward. The motor moves the chain or rotates the tire again, but this time without any help from you.


The more the throttle is twisted, the faster the electric bike will run. It is similar to a motorcycle, but not so fast. However, electric bicycles with only throttle function are not common. More common electric bicycles will be equipped with both accelerator and pedal assist motors, or they will only be pedal assist.

So do you have to step on the pedal to make it work?

If you have an electric bicycle with a throttle, you can choose not to pedal at all. However, this does drain your battery quickly. If you have a pedal-assisted electric bicycle, also known as an “electric bicycle”, you must step on the pedal to start the motor.

Does the electric bicycle charge itself?

There are technologies that allow electric bicycles to charge themselves while you are riding, but this is not a very popular or common feature. The main way for bicycles to charge their batteries is to use “regenerative” braking. The sensor will detect when you use the brake, trigger the motor to enter the reverse mode, and then use the excess energy to charge the battery.


Unfortunately, this technology makes the battery components of the bicycle significantly heavier, and only 5-10% of the braking energy loss can be fed back to the battery.


This means that in a 10-mile trip, your battery can last an extra mile. Due to the extra weight of the charging assembly, this small charge is usually not worth it. Therefore, most electric bicycles do not have this function.

In this article, I will learn more about electric bike batteries and their charging.

Do you need to change gears on an electric bike?

Some electric bicycles do not have gears, and these are called single-speed electric bicycles. That being said, most electric bicycles do contain gears. Most commonly, an electric bicycle will have 5-8 gears that cycle through when you pedal.


Therefore, if you have a single-speed electric bicycle, you do not need to change gears. If your electric bike does have gears, you will want to change them while riding, starting with the lowest gear (paradoxically, the highest numbered gear).


You need to change gears because riding in a consistent low gear will make your engine work harder and drain the battery. Riding in a high gear (lower-numbered gear) will make pedaling easier.


Most people prefer to install gears on their electric bikes so that they can better control the effort they put in riding. This also allows them to control how much battery they use and make it easier to ride when the battery is depleted.

How electric bikes work

How to change gears on an electric bike?

In terms of shifting gears, treat electric bicycles as ordinary bicycles. Start pedaling at the lowest gear and gradually shift gears as you step on the pedal.


Depending on the gear type of your electric bike, this can be done by turning the gear lever or switching with your thumb, both of which are usually located on the right handlebar. If you want to stop, try lowering the gear.

How to change the pedal assist level of an electric bicycle

Changing the level of assistance provided by the motor is another way to control how much energy you invest in riding and how much battery power you use.


On the left handlebar of the Pedal Assist Electric Bike, you should find the button that controls the Pedal Assist System (PAS). Sometimes this can be found on the central control panel, but each manufacturer is different, so you may need to find where these are on your particular electric bike.


These buttons will cycle through the different levels of help the motor will provide. At the lowest setting, you will use very little battery power to do most of your work. At the highest setting, you do the least amount of work, but the battery will drain quickly.


On throttle-assisted electric bicycles, only the throttle is used to change the speed, usually by twisting. A small twist will provide the least help from the motor, and a larger twist will give you more help. The difference between this and PAS is that you don’t have to use the gas pedal at all. If you choose not to pedal, adjusting the accelerator will only adjust the speed of your electric bike.


But remember, just like adding electric pedal assist, using the accelerator will quickly drain the battery.

The following is a list of common electric bicycle assist modes based on Bosch motors.

Environmental protection – 40%
Sports – 150%
Turbocharging – 225%


Having 100% power assist basically means that the electric bicycle will match your power. Given that the cyclist will generate 100 watts of power at a reasonable speed, this means that the bicycle will receive 200 watts of power. At 225%, you may contribute 100 watts, and the bicycle contributes 225 watts, for a total power of 325 watts.


Considering that professional cyclists generate 300 watts of power on average, you will understand why people say that riding an electric bike is like someone pushing you forward.

The working principle of electric bicycle motor

As I mentioned before, the electric motor is the driving force that drives the electric bicycle forward when it starts. There are different types of motors used in electric bicycles, each of which works in a unique way to propel the bicycle forward. First of all, here are some useful common motor terms.


Common terms
Torque A measure of the force of rotating something around a central axis.
The cadence sensor measures how fast you step on the pedal.
The torque sensor measures how hard you step on the pedal.
Watt A measure of power.


Motor type
There are two main types of motors on electric bicycles:

Wheel drive motor
Mid-mounted motor
The hub drive motor is located on the front or rear hub of the bicycle, which is the center of the wheel. It is more commonly seen that the rear hub hub drive motors are those that are usually modified in front of the motor, which means that someone has attached the motor and throttle to a regular bicycle.


Having said that, as manufacturers experiment with different designs, front hub motors are becoming more and more popular.


The central drive motor is located near the bicycle crank, which is located in the center of the bicycle frame. This motor is used for all pedal assisted electric bicycles. They are generally more expensive but more energy efficient than in-wheel drive motors.

How does the hub motor work?

There are two types of hub drive motors; direct drive hub motors and geared hub motors. Both basically attach to the wheel and generate torque to move the wheel.


The direct drive hub motor will rotate around a fixed shaft, which is the rear axle of the wheel and drives the wheel. The wheels rotate as a result, and the electric bicycle will move forward. Since the central axis remains fixed, this type of motor is the only motor that can enter the reverse mode and therefore use the regenerative braking discussed earlier.


There are many gears inside the geared hub motor, and these gears are connected to the hub. When the motor rotates, the motor shaft rotates the gear at a slower speed, generating torque, and pushing the bicycle forward again.


Essentially, both types of hub motors are connected to the wheels and move the electric bicycle by directly rotating the wheels. These motors put more pressure on the tires and are less energy efficient, but they are a cheaper option.

How does the mid-drive motor work?

The mid-drive motor adds another step to the process of turning the wheels. It is located in the middle of the electric bicycle, and the shaft is connected to the chain of the bicycle. When the motor spins, this moves the chain, then turns the wheels and propels the bicycle forward.


Because the motor is connected to the chain of the bicycle, it fits well with the natural gear system of the electric bicycle, making it more energy-efficient, while the hub drive motor is often a single-speed motor. However, this can be more expensive and will put more pressure on the chain.

How electric bikes work

What is motor power?

The power of an electric bicycle motor is measured in watts. This is the maximum output power of the motor, but it may run at a lower output, depending on the assist level selected.


Electric bicycles can have a variety of motor sizes, usually ranging from 250 watts to 1,000 watts. Unfortunately, a more powerful motor will be bigger and heavier, so you may need to compromise to use a smaller motor to reduce weight.


These numbers represent how much energy the motor can take from the battery to convert electrical energy into mechanical energy. In contrast, a professional cyclist can generate about 400 watts of power in an hour. This means that most motors will feel as if a professional cyclist is pushing you forward.

How to use the pedal assist with the motor?

Pedal assist is more commonly used for mid-drive motors, but it can be applied to both at the same time using sensors. The sensor will detect how hard you step on the pedal and adjust the power of the motor accordingly.


There are two types of sensors in the pedal assist system. These include cadence sensors and torque sensors. The cadence sensor will measure how fast you step on the pedal, and the torque sensor will measure how hard you step on the pedal. If the bicycle uses two sensors at the same time, motor assist will be the most accurate.


For its part, the cadence sensor will detect a slower pedal when you try to take off and cruise at higher speeds. In both cases, you may step on the pedal at the same speed, but require different levels of help.


A torque sensor is measuring how much power you need to be a little more accurate, but it will not be 100% correct when it is. This is why, if you have to choose, a torque sensor is a better choice. But when both are used, the pedal assist system works best.

How does an electric bicycle battery work?

The battery of an electric bicycle is a source of energy. When looking at the battery, you may encounter some confusing terms, so here are the most important terms to understand.


Common terms
How fast volts (V) current will flow.
Power/Watt (w) The rate at which work is completed, in watts.
Ampere (A) The amount of electricity (electrons) that flows through a certain point per second.
Watt hour (Wh)
Wh = Ah x V measures the power delivered over one hour.
Ampere Hour (Ah) measures the amount of electricity over an hour.
Range How far a fully charged battery can allow your electric bike to travel.


The battery will store energy and can be used to power the motor when needed. The motor converts electrical energy into mechanical energy to propel the bicycle forward.


When you buy a battery, you may get the battery voltage and ampere-hours. As mentioned above, voltage tells us how fast electricity can be transmitted, and ampere-hours indicate how much electricity the battery can provide in an hour.

Voltage and ampere hour

Increasing the voltage will make the electric bicycle faster, while increasing the ampere hour will increase the battery life.


These two factors can be multiplied to calculate the battery’s watt-hours, which means how much power is delivered to the motor in one hour. In a typical electric bicycle, this range is 300-1,000Wh.


Watt-hours make it easier to measure battery power because there are many different combinations of voltage and ampere-hours in the battery. Watt-hours give us a number for comparison.


A fully charged battery allows you to travel for miles before the battery runs out. This is called the range of the battery. This is affected by many variables, which I will discuss further later, but on average, an electric bicycle will use 10-20Wh per mile.


This means that for a smaller battery (300Wh) and using 20Wh per mile, you will be able to travel 15 miles on one battery. If you save battery, use about 10Wh per mile and have a larger 750Wh battery, you will be able to travel 75 miles.

Watt hour

Increasing the watt-hours will also increase the battery’s cruising range.


However, this assumes that you are using a pedal assist motor. If you use the throttle, your battery life will be much smaller (if you only use the throttle). This is because when it comes to pedal assist motors, you will contribute to power. Therefore, the electric power required for the electric bicycle is divided between you and the battery.


To use the throttle, you need to compare the power of the motor with the watt-hours of the battery to get the number of hours that the throttle can be used. If the battery has 1,000Wh, a 200w motor should be used for 5 hours, but a 750w motor can be used for about 1 hour and 15 minutes.


These are very simple examples, but they should give you an idea of how the battery works with the motor to power your electric bike.

How electric bikes work

What kind of battery does an electric bicycle use?

Most electric bicycles use lithium-ion batteries. The lithium ion battery is the same as you find in a mobile phone or laptop. The benefit of these batteries and the reason they are so widely used is that they can be used for a long time.


This is because their energy density is high, so they can hold more power than other batteries of the same weight. Considering that weight is a major disadvantage of electric bicycles, and it will actually affect battery life, this is currently the best choice for electric bicycles.


The working principle of lithium ion batteries is that positively charged lithium ions move through the battery and then release negatively charged electrons through an external circuit. These electronics provide electricity for your electric bicycle.

Lithium-ion batteries are also rechargeable. This is done by reintroducing electrons into the circuit and resetting the lithium ions. During the charging cycle, they will all move back to the other side of the battery.


Unfortunately, no battery can be used forever, as you experience when the car battery is dead or you have to throw away the old rechargeable AA from the camera. The same is true for electric bicycle batteries.


Depending on usage, lithium-ion batteries can only be charged a certain number of times. On average, they need to be replaced every three years. But for those who do not use electric bicycles every day, their batteries can last up to 10 years. It all depends on the frequency of charging.


Some people may be cautious about lithium-ion batteries for safety reasons. As we all know, some lithium-ion batteries explode when they are overcharged or overheated. This is why they are not allowed to board the plane. However, modern batteries will be equipped with circuit breakers to prevent overcharging, thus making them safer.

How do you charge the electric bicycle battery?

Charging the battery of an electric bicycle is very simple. It will come with a charging cable, and you can plug it into any regular power outlet. It may take 3-6 hours to charge a fully exhausted battery.


This is why most people charge their batteries at night, or if they ride a bicycle to work, they can charge at their desks during the day.


However, not every electric bicycle is the same. Some batteries are installed externally, some will be semi-integrated into the frame, and some will be completely enclosed within the frame.


The ones inside the frame are inaccessible, which means you can’t take out the battery to charge it. You need to bring the entire bike to the power source.


The semi-integrated and external battery is removable, which means you can take the battery with you to your home or office for recharging. These batteries are usually locked in place with a key to prevent theft.

What affects the use of the battery?

There are many variables that affect the battery life of an electric bicycle. Some you can’t control, but some you can.


Battery size: A battery with more watt-hours will increase your cruising range.


Motor size: A more powerful motor will use more battery energy.


The weight of the bicycle and the rider: Increasing the weight of the bicycle, whether it is the bicycle itself or the rider, will increase the resistance during riding, which will consume more battery energy.


Uphill and downhill: Uphill will require more battery power, while downhill will save energy. So if you live in a hilly area, the battery will usually not last that long.


Terrain type: Rough terrain, such as grass or gravel, will increase the resistance of the bicycle and require more power.


Wheels: Heavier and wider tires provide more resistance when riding, which drains the battery.


Assist type (gasoline and pedal assist): As we all know, pedal assist motors are more energy efficient because they constantly adjust the amount of power used. In a more relaxed ride, they will consume less power from the battery.


Assist level: On pedal assist bicycles, you can choose to reduce the amount of assistance provided by the motor when pedaling. This usually ranges from less than 100% (referred to as “ecological mode”) to about 300% (often referred to as “turbine mode”). Even with the throttle, you can choose to twist in smaller increments to use less power. The less help you use, the longer the battery life will be.


This article has answered any questions you have about how electric bicycles work and prepares you for buying and riding your own electric bicycle. Understanding the working principle of electric bicycles will help you have more riding pleasure, and hope to encourage you to take good care of it.


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