How to choose an electric bike according to the motor

Users in the purchase of electric bicycles, there are two factors are most important, one is the battery capacity, the second is the motor performance. Battery capacity is not necessarily the larger the better, after all, the battery is too heavy will also have a certain impact on the range; but a good motor with the range, speed and other driving relationship is very big. In addition, from the aspect of matching between accessories, many users only think that the battery power is large, the speed of the electric car will become faster. In fact, such an idea is wrong, both the battery and the motor (even including the controller) are needed to match reasonably in order to make the electric car reach the maximum efficiency. Once the battery power is large, it may burn the motor, leading to its performance decline, and even can not be used normally.
electric bike
Other users like to modify their electric bikes privately. In terms of electric bicycle power alone, in recent years, thanks to the improvement of motor technology and the decrease of battery cost, electric bicycle power has been greatly improved. Although the increase in battery and motor power can be a big boost to speed. But in the long run, it will also speed up the loss of accessories to the motor, which is one of the main reasons why many users find that the motor is not as durable as the original. If you want to modify the motor, you need to match the motor with the battery and controller in a reasonable range, not a single pursuit of power, otherwise it will damage the life of other accessories.
Users purchase, what kind of motor suitable for their road conditions, we will briefly introduce the following.

Wheel motor
Hub motor is the power, transmission and braking device are integrated into the wheel hub. This technology was first applied to cars, as early as 1900, Porsche has made an electric car equipped with a wheel hub motor in the front wheels. With the development of electric vehicles, hub motor technology is not what it used to be.
The advantages of the hub motor are the mature design and relatively low price, which occupies most of the market of electric bicycle. However, since the motor is integrated into the wheel, it will break the front and rear weight balance of the whole vehicle, and will be affected by the impact of bumps when off-road in mountainous areas; for full shock models, the rear hub motor will also increase the underspring mass, and the rear shock will need to deal with greater inertia impact.
electric bike
There are three ways to install wheel motors.
1. Rear wheel: This is also the most common installation method. Compared with the installation on the front wheel, the rear triangle is more stable and reliable in terms of structural strength, and the transmission of torque pedal signal and alignment will also be more convenient.
2. Front wheel: Some small and delicate city cars with small wheel diameter generally choose the front hub solution in order to take into account the internal shift hub and the overall appearance of the vehicle.
3. front and rear wheels: In pursuit of more powerful power, some electric vehicles are equipped with motors for both front and rear wheels, rated at up to 1000 W. It should be noted that China's new national standard stipulates that the rated power of electric vehicles and electric-assisted bicycles shall not be higher than 400 W, the European Union shall not be higher than 250 W, and some parts of the United States shall not be higher than 750 W.
electric bike
In addition to the different power levels, the complexity of their control is also different. When the electric vehicle is turned off or the battery is dead, the clutch device (usually a planetary gear, which plays a lever-like role in the motor, it can reduce the speed and amplify the output torque) designed inside the geared hub motor makes the vehicle glide or human pedaling with less resistance than the same situation with a gearless hub motor.

To put it simply, when the electrical system is turned off and the vehicle is coasting or pedaling, the resistance of a geared hub motor is less than that of a gearless motor. This is because a gear hub motor is usually designed with a clutch device inside, and the force of pedaling is broken down through the clutch device to act directly on the rear wheels, and does not drive the electromagnetic structure inside the motor to rotate, so it does not bring too much extra resistance.
electric bike
There is another kind of gearless hub motor (also called direct-drive motor), whose internal structure is more traditional, without planetary wheel reduction device, relying directly on electromagnetic conversion to generate mechanical energy to drive the electric vehicle. Gearless hub motors are direct drive type, which generally do not have a clutch device inside, so they also need to overcome electromagnetic resistance when riding in a power failure. The advantage of this structure of hub motors is that they can convert kinetic energy into electrical energy to be stored in the battery when pedaling or driving, but the electromagnetic conversion efficiency is not ideal.

A mid-mounted motor is a motor that is placed in the middle of the frame. The advantages of the mid-mounted motor are that it can keep the front and rear weight balance of the whole car as much as possible, and will not affect the shock absorber action, and the motor will bear less road impact, high integration, and more concise motor shape; when driving on the ground with poor road conditions, its handling, stability, and passability are better than the wheel motor models; with the same battery capacity, the unique power transmission structure and drive mode of the mid-mounted motor make its power and range both better. With the same battery capacity, the unique power transmission structure and drive mode of the mid-motor makes its power and range better than that of the hub motor.
electric bike
The mid-motor converts electrical energy into kinetic energy and does not apply it directly to the drivetrain, but rather through a series of derating devices that amplify torque and reduce speed. Therefore, for a mid-motor bicycle, the motor power output shaft and the bicycle's tooth plate shaft are structurally two shafts linked by a speed reduction mechanism in the middle. According to the difference of relative positions of these two shafts, the mid-motor can be divided into coaxial motor (also called concentric shaft motor) and parallel shaft motor.

One of the structure diagram of the parallel shaft motor: the left side is connected to the disk shaft, the right side white pinion is connected to the power output shaft of the motor, the two shafts are in a parallel position, and the middle is connected by a series of transmission gears.

Coaxial motor
This type of motor is mostly an external rotor motor, which uses the inner ring of the motor stator and the space on both sides to place the reduction system. Coaxial motors are also more difficult because it is not easy to achieve multi-stage reduction, torque, heat dissipation and concentricity of the drive shaft in a limited space.
electric bike
In many high-end or conceptual e-bike designs, a mid-mounted motor is basically used; however, in the national context, e-bikes are used as the main means of travel for reasons of economy and convenience. To put it in perspective, a mid-mounted motor has high torque, sufficient power and low starting current, which makes it more suitable for three-wheeled e-bikes and can maintain the overall appearance of the vehicle when converting from oil to electricity. Users with strong hands can also configure the transmission ratio according to the gears at will, fully utilizing the potential of the motor according to the usage requirements, and even designing their own transmission and clutch.

However, this modification will also increase the failure rate after the chain, gears and other transmission parts usually need to maintain maintenance.

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