Today we dive deep into the factors that truly how fast can ebikes go, from understanding motor components like windings and KV value to the impact of battery voltage and wheel diameter. Discover how to optimize your e-bike for exhilarating speed while maintaining efficiency.
Motor
The motor, as a power output unit, is one of the core components of an electric bicycle. The parameters and design of the motor largely affect the output speed of the motor and thus the maximum speed of the electric bicycle. The following are the structures and parameters that can affect the motor speed.
Winding
What is the winding of an e-bike motor
The winding of an electric bicycle motor is a component used to generate a magnetic field in the motor. It consists of a wire (usually an enameled wire) wound on the motor core in a certain way. The structure and parameters of the winding will directly affect the performance of the motor, such as speed, torque, efficiency, etc.
The following types of windings are commonly used in electric bicycle motors:
Concentrated winding: Concentrated winding winds all the wires on the motor core. It has a simple structure and is easy to manufacture, but the efficiency is low.
Distributed winding: Distributed winding evenly distributes the wires on the motor core. It has a complex structure and a high manufacturing process, but the efficiency is high.
Special winding: Special winding is designed according to the special requirements of the motor, such as to increase torque or reduce noise.
Why the more windings, the higher the motor speed
The relationship between the number of motor windings and the speed can be explained as:
The working principle of the motor is to convert electrical energy into mechanical energy using the principle of electromagnetic induction. In short, when current flows through a conductor, a magnetic field is generated. The magnetic field in the motor interacts with the fixed magnetic field to generate torque, which makes the motor rotate.
The role of winding
In a motor, the windings consist of multiple turns of wire wrapped around an iron core. When current flows through the windings, a magnetic field is generated at each turn. These magnetic fields add up to form a stronger magnetic field.
Number of windings and magnetic field strength
The more windings there are, the less current there is in each turn. However, because the number of windings has increased, the total current has increased. Therefore, the more windings there are, the stronger the magnetic field produced.
Magnetic field strength and speed
The motor speed is proportional to the magnetic field strength. That is, the stronger the magnetic field, the higher the motor speed.
Number of windings and speed
In summary, the more windings there are, the stronger the magnetic field generated and the higher the motor speed. This is why the faster Direct Drive motor looks much larger than the GEAR HUB MOTOR because it has many more windings.
for example
Assume that the number of windings of two motors is different, 100 turns and 200 turns respectively. Under the same other conditions, the current on each turn of the 200-turn motor is 1/2 of that of the 100-turn motor. However, since the number of windings has doubled, the total current of the 200-turn motor is twice that of the 100-turn motor. Therefore, the magnetic field strength generated by the 200-turn motor is twice that of the 100-turn motor. According to the working principle of the motor, the speed of the 200-turn motor is also twice that of the 100-turn motor.
KV value
Relationship between the KV value of the motor and the winding
The KV value of a motor refers to the no-load speed of the motor per volt of voltage. In other words, the higher the KV value of the motor, the higher the no-load speed at the same voltage.
The relationship between the motor KV value and the number of windings can be explained as:
KV value calculation formula
The calculation formula for the motor KV value is:
KV = No-load speed / voltage
Conversely, we can also say,
No-load speed = KV * voltage
The higher the KV value of the motor, the higher the no-load speed at the same voltage.
in:
KV value: The unit is RPM/Volt (speed per volt)
No-load speed: The speed of the motor per minute when it is not loaded
Voltage: The voltage applied to the motor, measured in volts (V)
Number of windings and no-load speed
As mentioned above, the more windings there are, the stronger the magnetic field generated by the motor is, and the higher the motor speed is. Therefore, the more windings there are, the higher the no-load speed of the motor is.
Number of windings and KV value
According to the calculation formula of KV value, the more windings there are, the higher the no-load speed of the motor is, and therefore the higher the KV value is.
For example
Assume that the two motors have different numbers of windings, 100 turns and 200 turns respectively. If other conditions are the same, the no-load speed of the 200-turn motor is twice that of the 100-turn motor. If 10 volts are applied to both motors, the KV value of the 200-turn motor is twice that of the 100-turn motor.
It should be noted that the number of windings is not the only factor that affects the KV value of the motor. Other factors include the motor’s magnetic circuit design, cooling method, etc.
Reduction ratio
GEARED HUB MOTOR is called GEARED because there is a GEAR BOX inside. The gear hub motor reducer used in electric bicycles is usually a planetary gear reducer. Planetary gear reducer is a compact, high-efficiency reducer. The gear material is usually nylon, which is very suitable for electric bicycle applications.
The working principle of the gear hub motor reducer is to reduce the motor speed through a series of planetary gears, so that the hub rotates at a slower speed. The transmission ratio of the reducer depends on the gear ratio of the planetary gears ( reduction ratio ) . The larger the transmission ratio, the more obvious the reduction effect.
There is an indirect relationship between the motor reduction ratio, the top speed of the e-bike and the torque.
- Definition of reduction ratio
The reduction ratio refers to the ratio of the motor output shaft speed to the input shaft speed. The larger the value, the more obvious the reduction effect.
- Reduction ratio and maximum speed
The relationship between the reduction ratio and the maximum speed depends on the KV value of the motor and the battery voltage. The KV value is the ratio of the motor’s no-load speed to its voltage, expressed in RPM/V (revolutions per volt). The battery voltage provides power to the motor.
Under the same battery voltage, the higher the KV value of the motor, the higher the no-load speed. The smaller the reduction ratio, the higher the speed of the motor output shaft. Conversely , the larger the reduction ratio, the lower the speed of the motor output shaft .
- Reduction ratio and torque
The relationship between reduction ratio and torque is more complicated. Generally speaking, the larger the reduction ratio, the greater the torque output by the motor. This is because the reducer can amplify the force of the motor.
However, higher torque usually reduces the speed of the motor. Therefore, under the same power, using a smaller reduction ratio can get a higher speed, but the torque will be smaller; using a larger reduction ratio can get a greater torque, but the speed will be lower.
Battery
Voltage
The KV value mentioned above is the no-load speed voltage coefficient. It is an important indicator to measure the relationship between the no-load speed and voltage of the brushless motor. It refers to the increase in no-load speed for every 1 volt increase in voltage when the motor is in the no-load state. The unit is RPM/V (speed per volt).
The higher the KV value, the higher the no-load speed of the motor at the same voltage. For example, a motor with a KV value of 1000 has a no-load speed of 10,000 RPM at 10V, while a motor with a KV value of 2000 has a no-load speed of 20,000 RPM at 10V.
The relationship between battery voltage and motor speed can be expressed by the following formula:
No-load speed = battery voltage * KV value
in:
- No-load speed: The speed of the motor when it is not loaded (RPM)
- Battery voltage: The voltage supplied to the motor (V)
- KV value: no-load speed voltage coefficient (RPM/V)
It can be seen from the formula that the battery voltage and no-load speed are directly proportional, that is, the higher the battery voltage, the higher the no-load speed.
In practical applications, the motor speed is also affected by other factors, such as:
- Motor load: The greater the motor load, the lower the speed.
- Motor efficiency: The higher the motor efficiency, the higher the speed.
- Controller performance: The performance of the controller will affect the operating efficiency of the motor and will also have a certain impact on the speed.
- Ambient temperature: In low temperature environments, the efficiency of the motor will decrease and the speed will also decrease.
for example:
Assume there is an electric bicycle with a 60 V battery and a motor KV value of 8 00. Then, the no-load speed of the motor is:
No-load speed = 60 V * 8 00 = 48 000 RPM
In actual riding, due to the existence of motor load, the actual speed will be lower than the no-load speed. For example, if the motor load is 50%, the actual speed may be only 24,000RPM .
In summary, the KV value can be used to measure the relationship between battery voltage and motor no-load speed. When choosing an electric bicycle or other electric equipment, you need to consider the matching of battery voltage and motor KV value to obtain the best performance.
Controller
The controller can directly affect the speed of the motor by controlling the current and voltage to the motor. For example, the controller can increase the current to the motor, thereby increasing the speed, or reduce the voltage to the motor, thereby reducing the speed.
It should be noted that the controller’s action is based on the battery voltage and motor characteristics. If the battery voltage is too low or the motor KV value is too low, the controller may not be able to increase the motor speed to the required level. In addition, excessive motor load will also limit the increase in motor speed.
In summary, the controller is one of the important factors that affect the motor speed, but it is not the only factor. When choosing an electric bicycle or other electric equipment, you need to consider factors such as battery voltage, motor KV value, motor load and controller performance to obtain the best performance.
Here are some frequently asked questions about motor controllers and speed control:
How does a motor controller control speed?
Motor controllers typically control speed by:
- Pulse Width Modulation (PWM): PWM is a technique that controls the on-time of a switching device. By adjusting the duty cycle of PWM, the average voltage supplied to the motor can be controlled, thereby controlling the speed.
- Hall Effect Sensor: Hall Effect Sensor can detect the speed and position information of the motor. The controller can adjust the current and voltage of the motor based on this information to achieve more precise speed control.
What is PID control?
PID control is a commonly used closed-loop control method used to control the deviation between the system output and the set value. In motor control, PID control can be used to control the motor speed to make it closer to the target speed.
Wheel diameter
The wheel diameter of an e-bike will affect the top speed, but only to a limited extent. Generally speaking, the larger the wheel diameter, the higher the top speed. This is because the larger the wheel diameter, the longer the distance traveled per wheel circumference, and the higher the speed at the same speed.
Specifically, the relationship between wheel diameter and maximum speed can be expressed by the following formula:
Maximum speed = wheel circumference * rotation speed / 3600
in:
- Maximum speed: in kilometers per hour (km/h)
- Wheel circumference: in meters (m), equal to the wheel diameter multiplied by π
- Speed: in revolutions per minute (RPM)
From the formula, we can see that the maximum speed is proportional to the wheel circumference, that is, the larger the wheel diameter and the larger the wheel circumference, the higher the maximum speed. For example, an electric bicycle with a wheel diameter of 26 inches has a maximum speed of about 28km/h at a motor speed of 1000RPM; while an electric bicycle with a wheel diameter of 28 inches has a maximum speed of about 32km/h at the same motor speed.
Load
We can use basic physics formulas to explain how load affects the top speed of an e-bike.
First, we need to understand that the movement of an electric bicycle is mainly affected by the following forces: gravity (Fg), friction (Ff), air resistance (Fa), and thrust provided by the motor (Fm). In an ideal situation, the relationship between these forces can be expressed as:
Fm=Fg+Ff+Fa
in:
- Gravity Fg=m⋅g, where m is the total load (including the weight of the rider and the bike) and g is the acceleration due to gravity.
- Friction force Ff=μ⋅Fg, where μ is the friction coefficient.
- Air resistance Fa=0.5⋅Cd⋅A⋅ρ⋅v2, where Cd is the drag coefficient, A is the frontal area of the bike and rider, ρ is the air density, and v is the speed of the bike.
The thrust Fm provided by the motor is related to the motor power P and the speed v of the bicycle, that is, Fm=vP.
Therefore, when the load increases (i.e. m increases), both Fg and Ff increase, requiring the motor to provide a greater thrust Fm to overcome these additional forces. If the motor power P is fixed, then in order to provide more thrust, the speed v of the bike must decrease. This is why increasing the load will reduce the top speed of an e-bike.
Please note that this is a simplified model and the actual situation may be more complicated because both friction and air resistance change with speed .
Imagine you are riding an electric bike, the bike is like a horse and the battery is like food for the horse. The more food the horse has, the farther it can run.
Now, let’s say you’re carrying a heavy backpack on a trip. The backpack is like an extra load. When you put the backpack on the horse’s back, the horse needs more food to run as fast as before. If the amount of food doesn’t increase, then the horse needs to slow down to make sure it has enough food to run to its destination.
Likewise, when you add an extra load to an e-bike (like a heavy backpack), the e-bike’s motor needs more power to maintain the original speed. If the battery charge is not increased, the e-bike needs to reduce speed to ensure that the battery power can support you to your destination.
Therefore, the increase in load will reduce the maximum speed of the electric bicycle. I hope this story can help you understand this problem.
Examples of How Fast Can Electric Bikes Go
How fast can a 48V 250W/350W e-bike go
Take this e-bike as an example.
https://jieli-electric.com/product/2022-250w-electric-folding-bike-tdn09z/
It is equipped with
- 250W GEARED HUB MOTOR
- 48V Li-ion Battery
- 20-inch wheels
According to our test, the maximum speed of the electric bicycle is about 20MPH.
How fast can a 52V/750W ebike go
Take this ebike for example.
https://jieli-electric.com/product/2022-lynx-750w-female-shorty-friendly-retro-electric-moped-bike/
This model equipped with
- 750W GEARED HUB MOTOR
- 52V Li-ion Battery
- 20-inch fat tire wheel
Compared to the car above, it has a higher battery voltage, a larger wheel diameter (because it is a fat tire), and more motor windings. According to our tests, its top speed is 28-30 MPH.
How fast can a 60V/2000W ebike go
https://jieli-electric.com/product/60v-2000w-direct-drive-fast-electric-bike-d2000/
The D2000 is our latest product, this electric bicycle is equipped with
- 2000W DIRECT DRIVE MOTOR
- 60V lithium-ion battery (17S battery, maximum voltage 71.4V when fully charged)
- 20-inch fat tire wheel
Compared with the previous car, it is equipped with a DIRECT DRIVE MOTOR, without a reducer, and the battery voltage is significantly higher. According to our test results, its top speed has reached an amazing 44MPH, and because of the power, even without reducer gear box, and the torque it outputs is also at a satisfactory level.
Summary: How to make an e-bike go faster
Choose a motor with powerful performance
one of the most critical components that affects the top speed of an e-bike . When purchasing, be sure to ask the seller about the parameters of the motor, such as power, windings, KV value, etc.
Increase battery voltage
The battery voltage powers the motor, and the higher the voltage, the more power it provides and the higher the top speed.
- Choose a higher voltage battery: When buying an electric bike, you should choose a battery with a higher rated voltage.
- Use multiple batteries: If the existing battery voltage is insufficient, consider using multiple batteries in series or parallel to increase the voltage.
Improve motor efficiency
Motor efficiency refers to how effectively the motor converts electrical energy into kinetic energy. The higher the efficiency, the less energy is wasted and the higher the top speed.
- Choose a high-efficiency motor: When buying an electric bike, you should choose a motor with higher efficiency.
- Maintain the motor regularly: Keeping the motor clean and lubricated can improve the motor efficiency.
Optimize the speed ratio
The speed ratio refers to the ratio of the number of teeth on the sprocket to the number of teeth on the flywheel. The larger the speed ratio, the higher the top speed.
- Choose the right gear ratio: When buying an electric bicycle, you should choose the right gear ratio according to your needs. For example, if you pursue high speed, you can choose an electric bicycle with a larger gear ratio.
- Use gear changes properly: During riding, you should use gear changes properly according to road conditions to maintain optimal motor efficiency and maximum speed.
Reduce the load
The load will increase the resistance of the motor and reduce the maximum speed. Therefore, the load should be lightened as much as possible.
- Reduce the weight of your load: Do not carry heavy objects or passengers on your e-bike.
- Choose the right tire pressure: Keeping your tires inflated can reduce rolling resistance.
- Avoid driving into a headwind: Headwinds increase wind resistance and reduce top speed.
- Choose a flat road: Try to ride on a flat road and avoid climbing hills.
Reduce wind resistance
Wind resistance affects the efficiency of the motor, especially at high speeds, where the effect of wind resistance on top speed is more pronounced.
- Choose a streamlined body design: A streamlined body design can reduce wind resistance.
- Wear tight-fitting clothing: Tight-fitting clothing can reduce wind resistance.
- Keep your helmet flat: The shape of your helmet also affects wind resistance.
Optimize control strategy
The motor controller can control the speed and torque of the motor. Optimizing the control strategy can improve the efficiency and maximum speed of the motor.
- Choose a controller with good performance: When buying an electric bicycle, you should choose a controller with good performance.
- Upgrade controller software: If the existing controller software version is lower, you can consider upgrading to the latest version.
It should be noted that the above measures are not completely independent, but affect each other. In practical applications, various factors should be considered comprehensively to obtain the best performance. In addition, attention should be paid to safe riding and compliance with traffic regulations.
Key takeways
The Engine of Excitement: Understanding Motor Components
Windings: These coils of wire are the heart of the motor, generating magnetic fields that propel your ride. More windings generally translate to higher speeds, but come with a trade-off in efficiency.
KV Value: This number reflects the motor’s no-load speed per volt. A higher KV value indicates a faster motor at the same voltage.
Reduction Ratio (Geared Hub Motor): This gearbox reduces the motor’s speed, translating it into higher torque (power) for tackling hills. However, a larger reduction ratio sacrifices some top speed.
Battery Power: The Fuel for Speed
The battery voltage directly impacts motor power. Higher voltage batteries deliver more power to the motor, leading to greater potential speed.
Beyond the Basics: Optimizing for Speed
While motor and battery are crucial, several other factors influence e-bike speed:
- Wheel Diameter:Larger wheels cover more distance per rotation, translating to a higher top speed.
- Load:Lighter loads reduce resistance on the motor, allowing for faster speeds.
- Wind Resistance:Aerodynamic designs and clothing minimize wind resistance, maximizing speed.
- Controller Performance:A high-performance controller efficiently manages motor power for optimal speed.
Examples to Illustrate the Power:
The post showcases how e-bike speed increases with better motor and battery combinations:
- 48V 250W/350W:Estimated 20MPH due to the lower power motor and battery.
- 52V 750W:Increased speed (28-30 MPH) due to higher voltage, larger wheels, and more windings.
- 60V 2000W:Blazing speeds of 44MPH achieved with a powerful direct drive motor and high voltage battery.
The Final Gear: Putting it All Together
Remember, these factors work together – a high-performance motor won’t reach its full potential with a low-voltage battery. To achieve the perfect balance of speed and efficiency for your needs, consider all these aspects.
Ride Responsibly, Ride Fast!
Always prioritize safety and follow traffic regulations while enjoying the exhilarating speed of your e-bike. This guide empowers you to make informed choices and unlock the true potential of your electric adventure!
Who We Are?
Jieli Electric is an experienced and professional electric bike manufacturer.
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Sales Manager at Jieli Electric Bikes.
Near 10 years experience in electric bike industry, researching/marketing/promoting e-bike is my daily life.
