what are the most crucial ebike parts

Electric Bike Parts Explained


Noel Joseph
August 6, 2021

Monday morning in New York City is a festival of sweat and tears.

You want to get to your office because your work-from-home just ended. Unfortunately, all forms of public transport are unreliable. You contemplate owning a car of your own. Then you laugh at yourself for thinking that.

The only solution to all your Monday morning NYC woes is an Electric Bike

Commonly referred to as e-bikes, these are pedaled cycles that also have motorized functions attached to them. They significantly reduce your efforts and do not pollute the environment as you sail across the traffic in your city. The machine itself sounds uncomplicated.

However, it is a combination of various devices and technical instruments. There is no better time than the present to get introduced to the fantastic commuter that is the e-bike. 

The Battery

ebike crucial parts

The battery pack is the most crucial feature of every e-bike. In fact, the battery is what transforms a regular bike into an electric one.

It is essentially the device that powers the e-bike. The science behind battery-powered machinery is pretty straightforward. The battery pack on an e-bike generates a current that runs an electric motor, ultimately reducing your pedaling efforts. 

Batteries are made of a variety of metals and alloys. A few years ago, most batteries, or “cells” as we then called them, were made using a Nickel-Cadmium combination or lead.

However, all those tropes have been replaced today with the groundbreaking lithium-ion battery. It is also called “Li-ion.” A Li-ion battery made of the highest quality material can last up to 5-6 times longer than an average lead-acid battery.  

What are e-bike batteries like, and who makes them?

Well, that’s an easy question to answer. Most tech companies manufacture batteries of their own. Companies like Panasonic, Samsung, and Sony manufacture these batteries.

Most e-bike batteries have the potential of 36V or 48V, although you will find 24V and 72V batteries as well.

The spectrum of voltage in e-bike batteries is the safest possible metric. Any lower than that, and you would have to use high-gauge wires and connectors. On the other hand, if you use a higher voltage than that, there is a chance of electrocution. 

How much power output does an e-bike battery deliver?

The power output of any battery is measured in a unit called “watt-hours.” Every battery has a voltage, measured in volts, and a capacity, measured in amp-hours.

When you multiply these two units, you get watt-hours. Thus, the total energy stored inside a battery can be determined using this simple formula. 

Most e-bikes have batteries with power outputs in the 300-800 Wh range. For comparison, an average electric car runs on a 64,000Wh battery. Most ebike manufacturers will put their batteries into the integral frame of the bike so that it does not ruin the bike’s aesthetic. Additionally, that structural integration keeps the battery safer. 

There is a slight problem with stock ebike batteries, though. These batteries last for a long time, and when the time comes to replace your original battery, it becomes a daunting task to separate it from the frame. Also, since it’s been years since you got the bike, there is a probability that your specific type of battery has been discontinued.

Some bikes mount their batteries behind the rider or in any external position to be replaced easily. These external batteries are open to conversion and can be upgraded whenever necessary. 

The Motor

about ebike motors

In the circuit powering your ebike, the next element is the motor. Quite literally, the motor churns the wheels of your bike.

It absorbs the current that is generated by the battery and converts it into mechanical energy. The motor can be located anywhere on the bike, but the rear wheel is the most common location.

Keeping the motor on the rear wheel allows for the most effortless conversion where you essentially replace a regular bike wheel with a motorized one. 

A large part of modern e-bikes run on the BLDC motor – a Brushless DC motor. This type of motor has three-phase wires connected to it to supply power. That system of a motor and its connecting wires is called a Hub. 

What are the types of e-bike motors?

You can break down hub motors into two main types – geared or direct drive. Geared motors are small and give a limited output. On the other hand, direct-drive motors are heavy and powerful.

The function of the bike itself best decides the choice of motors on an e-bike. If the bike is used for general commutes or leisurely rides, then a simple geared motor will do the job.

However, if you use the bike to ride steep slopes or lug up cargo, you need to fit a heavy direct-drive motor. 

How much speed do e-bike motors add?

To determine how much speed an ebike motor contributes, we need to learn a new metric – the motor winding constant.

It is, in essence, the number of times the motor will rotate the wheel for every voltage of the battery. It is represented by the symbol kV, and it can be calculated as rpm/V. 

If a motor winding constant is 10 rpm/V, the motor spins the wheel 120 times for a 12V battery, 240 times for a 24V battery, etc. 

Wheel diameter also plays a part in calculating the speed generated by a motor. The most commonly used wheel diameter is 26 inches. Also, most motors are wound to produce 8rpm/V.

So, if you have a motor that produces 100 rpm for a 26-inch wheel, the motor generates a speed of 12 kmph (approximately 7.5 mph). The higher the rpm generated, the higher the speed. 

If you are already pedaling faster than the motor is providing, it will stop providing any power output or go into regenerative braking mode. 

The Controller

controllor box

You might have heard of the battery and the motor, but you must not have known what a Controller is. It is simply the bridge between the two. Basically, you cannot connect a battery directly to a motor. Instead, the connection has to pass through a controller. 

Ever wonder how direct current from the battery is converted to alternating current for the motor? The answer is – the controller does it. It converts DC into three-phase AC for the motor to spin.

The controller is also in charge of adjusting the voltage from the battery. The battery voltage fluctuates according to the rider’s response. The controller considers various phenomena like the rider’s throttle signal, pedal sensor data, and current limits to decide the voltage necessary from the battery. 

The controller can adjust the battery voltage from anywhere between 0V to maximum potential. For example, if you are running a 48V battery pack and are riding your e-bike at 50% throttle, the controller will reduce the voltage to 24V.

Moreover, the battery will function like a 24V battery at 100% power output. Simultaneously, the controller also increases the current in the circuit by the necessary ratio.

Where is the controller located?

Most commonly, you will find the controller located inside the hub motor or the battery package. Mounting the controller inside the hub motor proves to be beneficial since it is positioned perfectly to maneuver the battery voltage.

However, fitting the controller in the battery package makes it difficult to be repaired or replaced. 

The other components

The battery pack, motor, and controller are the primary essential parts of every ebike. Without these elements, you have a regular standard bike on your hands and feet. 

Let’s look at a few other components that are commonly seen on e-bikes.  


ebike twist throttle

How does a rider control the amount of power generated by the motor? Using the throttle, of course. Regardless of how the rider is pedaling, they can regulate the motor’s power at any point in the ride. 

You will commonly find throttles in two variables – thumb throttles and twist-grip throttles. If you have seen and handled geared bicycles, you will find that gear-shifters are ridiculously similar to the throttle. Both devices also serve the same purpose. 

Throttles are linked to the controller using connectors, and every company uses different sets for these links.

However, throttle signals follow an industry standard – all throttles use magnets to detect throttle position and sit at about 0.8-0.9V when the throttle is off and can rise up to 4V as it is gradually engaged. 

PA and Torque Sensors

A PA sensor stands for Pedal Assist Sensor. It is a device that senses and analyzes the rider’s pedaling and engages the motor and battery voltage.

Similarly, torque sensors measure your pedaling ability and how hard you are pushing on the bottom crankset of the ebike. 

Both the sensors mentioned above are external components. As a result, there is no standardized method that these gadgets use to calculate their metrics. However, most e-bikes are compatible with a wide range of these gadgets. 


E-brakes are essentially brake sensors. Whenever the rider presses the brakes, the e-brakes alert the controller that you are pushing the levers.

People generally opt for e-brakes for safety reasons. E-brakes act as kill switches for the motor. Every time the rider presses the e-brake, the controller will alert the motor and shut it down. 

Alternatively, e-brakes can trigger and activate regenerative braking. However, this facility will only be available in bikes that assist regen-braking. Essentially, the activity of pressing the brake levers will set off a mechanism that will charge the battery pack on the bike. 

Today mechanical and hydraulic brake levers are available with e-brake sensors built right into them, making it easy for riders to gauge their ebike commutes. 


display with battery level indication

Every ebike manufactured holds a unique and detailed display as a dashboard for the rider. In fact, the display is one of the most prolific additions that bikes have seen in their evolution. It is a facet that excels in making biking digital. It adds the “e” to the bike. 

The display on your bike is hooked up to the controller. The magnanimous controller relays all the necessary information about battery voltage and motor speed to the display. Since each e-bike’s display is connected to its individual controller, there is no standardized way of calibrating and showing details.

However, each ebike manufacturer might have its own unique methods ready for dispatch. Also, since displaying information is not standardized, it is challenging to change displays on your bike.

The tech that surrounds ebike displays has outdone itself in the last few years. The latest e-bikes now offer Bluetooth communication with the rider’s phone, allowing them to use their phone displays for their ebike data. 

What is the difference between an e-bike and a motorcycle?

Fundamentally, a motorcycle and an ebike are siblings. They have both been created out of a two-wheeler vehicle where we did not want to utilize our energy.

However, the fundamental difference between the two is that a motorcycle runs on an ICE (Internally Combusting Engine) mechanism, whereas an e-bike works on an electrical battery. 

There do exist electric motorcycles that work on the same principle as that of an e-bike. However, to ride an electric motorcycle, you need a license and registration. On the other hand, you don’t need any documentation to ride an e-bike.

Moreover, you can ride your bike on specially designed infrastructure like bike paths. You cannot pull off the same feat with electric motorcycles. 


Ebikes are truly fascinating machines. They are an ardent symbol of growth, development, and progress. Collectively, we took a bicycle and made it better.

Ebikes run on electric batteries and cells. These cells generate a current that feeds into a motor. The motor then converts electrical energy into mechanical energy and makes the wheels of the ebike spin.

A controller facilitates the trade-offs between the battery and the motor. Moreover, it also provides the details of the same to the rider. 

Ebikes also feature accessories and gadgets that allow riders to understand and control the workings of their bike in real-time. The growth in ebike tech has been monumental in shaping the automotive industry.


Noel Joseph

Noel Joseph has been in the world of motor vehicles for a long period. Currently, he is enthusiastic about Electric & Hybrid Motors and is an independent researcher. He advocates for a clean and sustainable future and envisions utilizing his years of experience in mechanical engineering. His new venture here at CompactPower.com is to organize and simplify knowledge on Electric vehicles. He wants to build a space where people can talk about EVs and associated technologies with freedom.