How do Electric Bikes Work?


When I was recently looking to buy a new electric bike I wanted to know how they work. There are actually a wide variety of types of electric bikes which can work in different ways. This post will help to show you the ways in which electric bikes can work.

So, how do electric bikes work? Electric bikes work in a similar way to ordinary bikes but with a battery and motor. The motor uses power from the battery to make one of the wheels turn more quickly when you pedal or when you push on the throttle. 

There are actually a number of different types of electric bikes that can work in different ways. This can have a large impact on the ride and performance of the e-bike.

How Electric Bikes Work

Regardless of the type of electric bike, they will all make use of a motor and a battery.

  • The Battery

The batteries on electric bikes will be Lithium batteries that are very efficient and that can be recharged using a mains outlet. They are, however, expensive and can cost between $300-$800 this is what mainly drives the price of electric bikes up. The batteries can be removed from the bike and stored elsewhere. Depending on the specific e-bike, they will often be designed in a way that allows for the bike to be used in the rain without having to worry about damaging the battery.

The purpose of the battery is simply to provide power to the motor. The batteries can add a lot of weight to the bike and where they are placed can make a big difference to how the bike rides. They can be placed anywhere on the e-bike but you’ll normally find them either above the rear wheel or on the main frame. Having the battery above the rear wheel makes it easier to remove the battery but it causes there to be extra weight towards the rear of the bike which can affect handling. Having the battery on the main frame distributes the extra weight more evenly but it makes the battery a bit harder to remove.

  • The motor

The motors on electric bikes can come in a number of different forms but their main purpose is to make one of the wheels turn more quickly by using power from the battery.

The motors can turn either the front wheel or the rear wheel and their placement can have an impact on how the bike performs.

The amount of power in the motor will impact how quickly the e-bike will be able to get up to speed and but it will also impact the range that you will be able to get out of the battery. The size of the motors will have varying limits based on where you live but they can range between 250 watts and 750 watts. Having a larger motor will help you to get up hills more easily but it will mean that you won’t be able to get as much range out of the battery.

There are three main types of motors that get used on e-bikes, front hub, rear hub, and mid-drive.

  • Front hub motors

Front hub motors work by making the front wheel turn using power from the battery. These types of motors will rarely be found on pedal assist e-bikes. This means that you will only be able to use a front hub motor by using a throttle. Having the front wheel pulling you forward can create an unusual feeling and can make cornering a bit more difficult. Another thing that makes cornering more difficult is the extra weight towards the front of the bike caused by the front hub motor.

You’ll usually find these types of motors on cheaper throttle assist e-bikes and on conversion kits. This is because it’s normally easier to replace the front wheel than the rear since you don’t have to deal with the chain.

  • Rear hub motors

Rear hub motors work by making the rear wheel turn by using power from the battery. Having the rear wheel be the wheel that is providing power will feel more natural for most people and it also means that it can be used with both pedal assist and throttle assist electric bikes. Having the motor be located to the rear also means that the extra weight will be at the rear of the bike this is preferable for most people over having it placed towards the front.

Most higher end throttle assist electric bikes will have the motor placed at the rear since it allows for a better performance of the bike over having it placed at the front.

  • Mid-drive

Mid-drive motors get placed in the area of the bike where you pedal and, in recent years, they have begun to be made by some very big names in the electric motor industry. They work by making the rear wheels move more quickly when you pedal by integrating with the bike’s drivetrain. This means that you’ll only find mid-drive motors on pedal assist electric bikes.

Mid-drive motors allow for the extra weight to be distributed more evenly throughout the bike. This can make it easier to accelerate and to handle the bike. You’ll normally find mid-drive motors on the higher end models of pedal assist e-bikes.

 

Geared vs Direct Drive Hubs

If you’re thinking of getting either a front or rear hub motor then there are two different types of hubs that you will be able to get and they are geared hubs and direct drive hubs.

  • Geared Hubs

Geared hubs are the smaller of the two and they use an epicyclic gearbox that uses an outer gear with inner teeth to connect to the wheel it then has three gears inside of it with one of them connected to the motor itself. Due to the way these types of motors are designed it makes it easier for them to generate more torque when traveling at lower speeds. This helps to propel the bike forwards more easily. They can also be freewheeled without creating extra drag. The main problem with these types of hubs is that they are slightly louder than direct drive hubs.

  • Direct drive

Direct drive motors are larger and a part of the wheel itself. They have a big ring of magnetic earth metals connected in them. The motor works by making the outer shell spin when turning the throttle causing the wheel to turn as well. Due to their design, they are not so well equipped to generate torque at lower speeds which is why they tend to be large almost as large as the wheel itself. This adds weight to the bike and can cause it to be harder to pedal and to handle. The other issue is that they can not be freewheeled so if you want to cycle it without the motor then you will have to deal with increased drag. The advantage of these types of motors is that they are very quiet.

Pedal Assist vs Throttle Assist

There are two main types of electric bikes that you can get and they are pedal assist and throttle assist.

  • Pedal assist

Pedal assist electric bikes work by giving you extra power when you pedal and only work when you are pedaling. They are ideal for people looking to improve their fitness and it has actually been shown that they can help to do so. They also allow for you to control the level of assistance that you want to use via an LCD display. Being able to control the level of assistance is especially helpful in increasing the range that you can get out of the bike. By putting the level of assistance to a low setting you will be able to reduce the amount of work being done by the motor and increase the range of the bike.

Pedal assist bikes will vary the amount of power assistance being provided by the motor by using either a torque sensor or a cadence sensor. The harder you pedal the more power will be provided by the motor. Having it this way is ideal since it means that you will get a proportional amount of power based on the speed you are going. Getting a sudden jolt of power when going at a slow speed would make for an uncomfortable riding experience and the sensors prevent this from happening.

Torque sensors are the more premium sensors that are used on higher end e-bikes. They allow for more precise power adjustments based on your speed and they allow for a smoother riding experience.

Cadence sensors work by monitoring how fast the magnets on the chainring are moving past the magnet sensor. They serve the same purpose as torque sensors but they are not as precise. This means that if you expect to be stopping and starting often then they won’t provide as much of a pleasurable experience. They are, however, good for when you will be maintaining the same speed over a prolonged period.

  • Throttle assist

Throttle assist electric bikes make the motor turn the wheels when you push or twist a throttle. These types of electric bikes do not need to be pedaled to move but you can still pedal them if you want to. Many people like having throttle assist available to them for when they come up to difficult obstacles such as hills which is why many people opt to get hybrid electric bikes that have both pedal assist and throttle assist modes. The problem with throttle assist is that it won’t help you to improve your fitness much and the use of the throttle can drain the battery quickly so you won’t be able to get much range.

I have a more in-depth post about the advantages and disadvantages of pedal assist and throttle assist e-bikes here.

How Conversion Kits Work

There are conversion kits, that you can get, which allow you to turn your ordinary bike into an electric bike. They work by replacing one of your wheels with one that has a hub motor. The motors can be either pedal assist or throttle assist but throttle assist is more common.

The hubs will normally be front hubs since it is easier to replace the front wheel that the rear but there are rear hub conversion kits available.

Conversion kits are ideal since they are normally cheaper than a pre-built electric bike and they allow for you to continue to use your own bike. But, they will add about 30 pounds to the weight of the bike and they can’t always be used in the rain.

I have written more in-depth about conversion kits and their benefits here.

Related Questions

How far do e-bikes go? Electric bikes will normally have a quoted range of between 20-50 miles. The range that you will actually be able to get will depend largely on how you use it and the terrain that you cycle on. You can read about how far electric bikes go here.

How fast do e-bikes go? Electric bikes will normally be limited to a certain speed depending on your area. The max speed will vary between 20 mph and 28 mph in USA and it will be 15.4 mph in Europe.

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