- Do you really know the function of an electric vehicle motor? What’s its role? How it works?
Many electric scooter, electric skateboard, onewheel, and other types of unicycles’ have motor as definition. The motor together with battery and a motor controller (ESC) are composed of the electric power system.
And motor is like the "heart" of an electric vehicle. It’s main task is to convert the battery electric energy into mechanical energy to make the electric vehicle run. If you compare an electric scooter to a plant, the battery is carbon dioxide and water, and the motor is sunlight. Plants can convert carbon dioxide and water into organic substances and release oxygen under the sunlight; electric vehicles can only start when the motor consumes electricity and become a travel tool.
- Most of the electric scooter motors are supplied from China, if you understand the distribution of electric scooter motor factories and industrial chain in China, maybe you will not wrongly purchase motors from a unknown store.
According to the data searched on China’s largest factory sales platform (1688 and Alibaba), Most of the electric vehicle motors factories(except for car) are mainly located in Zhejiang and Guangdong province. And about 80% of them are expected to be electric scooters motors produced in Zhejiang province（mainly in Changzhou, Wuxi, Yongkang, Ningbo, Suzhou）. And about 80% of the electric skateboard motors are produced in the GuangDong province(mainly in Shenzhen, Dongguan). This is mainly driven by product development: The manufacturing bases of well-known electric motor brands such as Emma, Xiaodao and Yadi are mainly located in Zhejiang Province, while most of the electric skateboard brands such as Meepo, Backfire, Wowgo and other high end electric skateboard OEM factories are in ShenZhen and Dongguan.
- Different electric vehicles have different requirements for motors? How to classify motors? Which type is the best one?
The DC motors can be classified by various perspectives
(RPM: rotations per minute)
|High speed motor||Geared ,stronger power , big torque, If it runs under a heavy load, the rotor cannot rotate due to insufficient power and the motor is easily burned. So use a reduction gear to reduce speed. when speed is lowered down, the transformed pulling force (driving force) is obviously increased, and climbing with laoding will be very powerful.|
|Low speed motor||Less torque per weight,Less torque per watt,More audible noise,Shorter lifetime,Higher reliability,Commutator sparking, More EMI radiation, May need airflow to cool rotor,Low RPM. It has been eliminated by electric viehcle factories.|
|Without brush||Brushless motor||More torque per weight,More torque per watt,Less audible noise,Longer lifetime,Higher reliability,No sparking,Less EMI radiation, Can be completely encosed,Higher RPM|
|With brush||Brushed motor||Less torque per weight,Less torque per watt,More audible noise,Shorter lifetime,Higher reliability,Commutator sparking, More EMI radiation, May need airflow to cool rotor,Low RPM. It has been eliminated by electric viehcle factories.|
|With gear||Geared motor||Gears are used to reduce speed by high-speed brushless motors,.|
|Without gear||Gearless Motor||Gearless are direct-drive brushless motors, Low-speed and high-torque can be achieved by changing the rated speed of the motor.|
So according to above classification with features, You can have a general idea of the category of motor and what feature you want to get.This may too technical for users to understand, but if we classify it in this way, it may help way out. This is summary from market availbe motors and mostly used status:
|Electric viecle||Motor Types||Board types||Power range|
|Electric scooter/ Electric skateboard||Hubmotor||Commuting in city flat road||300W-500W|
|Electric scooter/ Electric skateboard||Hubmotor||Commuting in off road||500W-1000W|
|Electric scooter/ Electric skateboard||Hubmotor||For fun(climbing hills),for racing||1200W-3000W|
|Electric Scooter||Chain motor(Belt motor/planet gear box)||Off road||1000W-3000W|
|Electric Skateboard||Chain Motor(Belt Motor/ planet gear box)||for fun(climbing hills), for racing||3000W-8000W|
|One wheel/ Balanced Board||Hub motor||for fun /short distance commuting||300W-500W|
(Surely, there're many different types of playing ,welcome adds up in comments.)
Then next we mainly talk about motor key parameters and the difference between the chain motor and hub motor.
- So many types and different motors , how do I choose reliable one?
1.Know the key parameters of the motor: Power, Efficiency, Torque, Performance
1.1 Motor Power: The most important parameter of the motor is the power, because it decides many performance feature:
- the top speed
- the climbing angle
- the load capacity
- the trip range
Nearly all electric vehicles have a motor power rating that is given in units of watts. It indicates how much power the motor is capable of consuming. A motor with higher watts will be able to consume a lot of energy in a short time. The more energy a motor consumes, the more mechanical energy that it will convert to. Generally speaking, a higher power motor will accelerate more quickly, carry more heavier weight, and climb steeper slope.
1.2 Motor efficiency :
This is more complicated concept, because there’re many factors influence a motor’s efficiency. It mainly include stator copper loss, rotor copper loss, mechanical power loss, and some key material quality (eg. magnets). Eg. Many same model of scooters are marked with same motor power ,saying like both 300w, but the riding experience are slightly different. Even two motors have same rated power 300W, this doesn’t mean that they can convert same mechanical energy. This is because motor power doesn’t capture how the motor’s efficiency.
1.3 Motor Torque
Motor Torque is the force that rotates your electric vehicle’s wheel and propels you forward. It’s a very useful metric to measure how much work can the motor perform, and it’s given in units of Newton-Meters(Nm).It’s very important for evaluate the top speed and the climbing angle of an electric vehicle can reach.
Sadly most manufactures don’t provide the torque value, as far as our investigation , it mainly due to high cost of torque test equipment input. However, you can still estimate it using the relationship that power is equal to torque multiplied by revolutions per second (RPS) or Power (W) = Torque (Nm) x RPS.
DC electric motors produce their max torque at zero revolutions per second (also called “stall torque”) and zero torque at their maximum, unloaded revolutions per second. Peak power output is found at half the max revolutions per second and half the max torque.
1.4 Motor Performance
As we can easily found a motor spec , it usually mark motor power at xx W. You should figure out it’s maximum watts or rated power(also means continuous working power) from seller. Because max power and rated power are totally different. Max power means maximum amount of power the motor can consume for a short period of time. Rated power refers to the amount of power that the motor can sustain for a long time, thus rated power is much more important for picking up a motor. Also , in order to boost the product stats, some manufactures will mark peak power, which is often 2 to 5X greater than continuous power, and peak power usually can sustain for very short time, often sustain for seconds.
2. Get aware of it : Spec in theory and in reality
A motor’s power changes over time, and it depends on several other factors. It mainly influenced by following factors:
2.1 motor temperature, when motor is heating up, it will become less performant. That makes difference of max power and continuous working power.
2.2 loading and road status.
A fat weighty rider will consume more power than a light weight rider. Also a flat road will consume less power than a grass ground.
Therefore , most of the time, the motor is not working in max power , it’s work in your actual real world, you may meet driving traffic, more braking and stopping , turning to avoid obstacles, climbing up and down hills.
This will be a real environment factor for you to consider in picking up a truly needed power of a motor. How to estimate the motor power? Usually the motor is marked with maximum power, then the rated power could be 50% of the max power, Or. If there is marked peak power , then rated power may be 20%-50% of it.
3. Get aware of your needs
Got well aware of your actual needs, what you want is for commuting ? or for off-road riding ? or for racing play? Then make correct choice of the motor power. Bigger power is better for top speed and climbing hills or in off road, but it doesn’t mean the bigger the better in your needs. You may have some loss in the weight of your electric vehicle, or loss in a perfect size. Bigger power also requires bigger battery pack, because it consumes power very quickly.
4. Mostly used motors in electric scooter and electric skateboardNormally often used hub motor and chain motor in electric scooter, electric balanced board, electric skateboard
Now here is a simple conclusion summary for the comparison between Hub motor and Chain motor
|Referene factor||Hub motor||Chain Motor|
|Power||most of market scooter power range is 2500-500W fewer electric scooter use high power (2000-3000W)|| most market chain motor power is > 1000W
many skateboard use high power motor(2000-3000)
|Torque||less torque||higher torque|
|Efficiency||Lower effiency due to weaker heat dissipation||higher efficiency due to higher heat dissipation|
|Assembly||inside wheel, easy for setup||Need extra chain and gear,much more complicated|
|Size and Weight||big size and much heavier||small size and light|
|Wheels choice||size much match with hubmotor||can match with multiple size of wheels|
- Some small tips for purchasing motor
1. Ask for the shop seller where the motor origin is : as explained in beginning, most electric scooter hub motors are well developed in east coastal city in China. And most electric skateboard motor is well developed in southeast of China.
2. Ask for the shop seller to provide motor torque test report. The ones that can be provided are generally large-scale electrical machinery factories, which generally wholesale to complete vehicle factories, and rarely provide external retail. Even if there is, the price is high.
eg. Here is our 11'' 72V 3500W hubmotor torque test report
If no such torque report is provided, it doesn’t mattery, you can calculate it(refer to above) normally, most of them cannot be provided.
3. Ask about the specifications. If the store tells you the specifications with certainty and cannot provide a report, the half rule will be adopted.
4. Testing: ask if the store has the conditions for testing. If the store has test equipment, it's quite possible a factory store. But most resellers don't have test equipments for motors.This is not big key point.
- After purchasing a motor, Can I program it?
If you buy a finished good, the manufacturer has designed a controller for this model of motor before shipment, and it has been calibrated and debugged. This kind of motor cannot be debugged.
If you buy a motor with a VESC controller, then this type of controller supports automatic motor calibration, and the performance can be perfectly matched. For how to adjust the parameters of vesc, you can refer to this blog.
Some scooters, like the Xiaomi M365, have firmware hacks that allow you to change the power output from the controller, which improves scooter performance (but reduces range and potentially battery life).
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