As electric bicycles become increasingly popular, their convenience and low-carbon properties make them an irreplaceable mode of transportation. The motor on an electric bicycle provides additional pedaling assistance to the rider, making cycling more effortless. As a core component of electric bicycles, different motors affect the performance of electric bicycles. Currently, the motors on the market mainly consist of hub motors and mid-drive motors. In terms of market share, hub motors have an absolute advantage. However, in recent years, high-end models that are popular in Europe and America are mostly designed with mid-drive motors. So, what are the differences between these two types of motors? This article will summarize the differences and advantages and disadvantages of these two types of motors in detail.
A hub motor, as the name suggests, is a design that combines the hub and the motor. Its biggest feature is that it integrates power, transmission, and braking devices into the hub. Thanks to its mature design and low price, it is widely used in electric two-wheelers and the power design of automobiles.
- Simple structure, no need for maintenance
The structure of the hub motor is simple, usually composed of coils, axles, magnets, and outer casings. Due to its simple structure, the failure rate of the hub motor is relatively low, and it basically does not need maintenance. It is independent of the pedal drive system, and it does not add any additional pressure to the chain or gear shifter, causing wear and tear on other parts. The chain of the electric motor vehicle may have a longer lifespan compared to non-electric bicycles.
- Low price, high efficiency
The production technology requirements for hub motors are low, and the manufacturing cost is low. A standard hub motor costs only 200 yuan, and motors over 500 yuan have the function of kinetic energy recovery. In terms of performance, the hub motor has a high electrical energy conversion efficiency and is more energy-efficient. Since the hub motor directly drives the rear wheel, there is no energy loss in the transmission process, and the energy conversion rate is currently around 80%. The hub motor operates with a uniform current and relies on electromagnetic induction to operate, making it quiet and less prone to wear. It is also easy to install, disassemble, and maintain.
The hub motor has a significant impact on the control, comfort, and reliability of the suspension of the entire vehicle. It does not handle shocks well, reducing the comfort of riding. It is more suitable for low-speed commuting below 40km/h. At high speeds, the vehicle is prone to wheelie.
- Easy to damage
The precision motor is placed in the hub, which is subject to severe up and down vibrations and harsh external environments (water, dust), making it prone to failure problems. When it involves tires, rims, and flywheels, the hub motor may be subject to more restrictions, making it more difficult to replace tires.
- Poor heat dissipation
The hub motor performs well at low speeds, but it is easy to generate a lot of heat during high-speed operation. The poor internal heat dissipation environment not only easily causes the decline of motor performance but also may burn the tires.
Hub motors can be further divided into geared hub motors and gearless hub motors. Geared hub motors have internal planetary gears that can reduce the speed of high-speed motors. Gearless hub motors do not have gearing devices and directly connect the low-speed motor shaft to the bicycle. The biggest problem with geared hub motors is the gears, which wear out quickly. Gearless hub motors only have bearings and no other moving parts, so there is basically no wear and tear. As long as the bearings are not rusted or worn out, they can be used almost indefinitely, making them more widely applicable.
A mid-drive motor is located at the bottom of the bicycle frame between the pedals and connects directly to the crank. The mid-drive motor is integrated into the electric bicycle frame and is not an independent unit like the hub motor. It does not directly provide power to the wheels but requires the bicycle's transmission system to provide power to the rear wheel. The motor rotates the crank and chainring, and the chain transmits power to the rear wheel.
- High efficiency, large torque
The biggest advantage of a mid-drive motor compared to a hub motor is its gear ratio. The rider can use the same chainring and gears as the pedals to provide power to the rear wheel, allowing for low gear ratios to provide power or high torque when starting from a stop. A low-speed mid-drive motor can outperform a hub motor of similar power when climbing hills, with longer endurance. Mid-drive electric bicycles use a torque sensor to transmit power smoothly, providing a better riding experience.
- Reasonable weight distribution, suitable for sports vehicles
The mid-drive motor is located in the middle of the vehicle, and the weight distribution is relatively balanced, allowing for maximum balance of the electric bicycle. During high-speed driving, it does not affect the shock absorption, and the impact on the motor is smaller. The integrated design reduces the exposure of lines and cables, and is superior to vehicles with hub motors in terms of off-road controllability, stability, and passability.
- Low resistance
The hub motor generates electromagnetic resistance as the battery power is depleted, making pedaling more difficult. In the case of no electricity, pedaling becomes more difficult. The mid-drive motor, on the other hand, has no magnetic resistance, and the internal design of the clutch allows the motor to be completely disconnected from the central gear when not in use, allowing for easy pedaling like a mechanical bicycle, even when the battery is depleted.
- Complex structure, high price
The internal structure of the mid-drive motor is complex, requiring not only a motor but also a clutch, transmission shaft, transmission chain, gearbox, and differential. Compared to hub motors, mid-drive motors are more expensive. Building a vehicle with a mid-drive motor, including the vehicle, motor, and battery, typically costs over $4,000. These parts not only increase complexity but also require regular maintenance and repair. The difficulty of modification is also greater, and the risk of failure is higher. Replacing the motor is also more expensive than just replacing the hub motor.
- Transmission system more prone to wear
Since the power needs to be transmitted through gears and chains to the rear wheel, the wear on gears and chains is greater than that of hub motors, and the chain needs to be replaced when it is severely worn. Otherwise, the chain may break, and you will have to push the vehicle home.
Currently, mid-drive motors are the best solution for mainstream products on the market due to their lighter weight, higher efficiency, and better riding experience. They are typically used in high-end electric bicycle models and are more suitable for off-road vehicles with high performance requirements. Hub motors have price advantages and low maintenance costs, and are environmentally friendly and cost-effective. Some people prefer the power and reliability of hub motors during off-road use, while others prefer the lightweight and concealed mid-drive motors for commuting. However, the price of a mid-drive motor vehicle is generally over ten thousand yuan, which may not be affordable for ordinary consumers. Hub motors can basically meet their needs.