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The science behind accurately testing electric vehicles accurately revealed by Su-vastika

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The science behind accurately testing electric vehicles accurately revealed by Su-vastika

November 07
13:16 2022
The science behind accurately testing electric vehicles accurately revealed by Su-vastika
Su-vastika’s Automatic Testing Setup for EVs
Su-vastika’s focus is on designing the Automatic Testing Equipment for testing Electric Vehicles so that we are able to help the Electric Vehicle Industry to test all the parameters to ensure the reliability of Electric Vehicles.

There is no denying the fact that if the EV industry needs to be successful, then we need to have testing set-ups in manufacturing as well as service stations.

But is it possible to do a full EV test?

The answer is yes, thanks to Su-vastika’s Automatic Testing Setup.

Let’s understand it with an example of an electric scooter.

What all needs to be tested and what is the different equipment required to test those components?

So, the electric scooter or 3-wheeler has 3 major components, and the major ones are the battery, controller, and motor.

All these components need to be checked individually as well as in synchronization. Everyone is interested in knowing the mileage of the electric scooter or electric 3-wheeler, which is to be calculated based on the efficiency of the complete scooter and needs to be checked for synchronization of all three components.

So even the efficiency will be checked on different loads so that we are clear that the mileage will be different on different loads.

Then the controller needs to be checked to see if it has a square wave or sine wave so that the quality of power given to the motor is checked.

Also, we can see that in certain scooters when moving there is absolute silence, but in other scooters, there is a slight noise in the motor which is there because of the waveform of the controller. In such scooters, cheap controllers are installed in the 3-wheelers and 2-wheelers that come from China.

Then after applying the load, how much THD is increased in the motor is another important parameter that needs to be checked. As the power supplied by the battery goes to the motor through the controller of the electric scooter, More THD will cause more wear and tear on the motor and reduce the life of the motor as more THD increases the heat inside the motor.

Then we need to check the overload of the controller and at what wattage the controller gives the signal to the motor to stop. The load is applied to the controller by loading the motor with the load. At which wattage the overload happens and how fast the controller behaves needs to be checked so that the life of the battery and motor is maintained. If the overload is not properly set in the controller, then the life of the motor can be a big challenge as it will overload the motor on various occasions and the motor can be damaged.

This can be understood in terms of how many people can sit on the scooter, and the scooter can take those people and can run.

I see a lot of people showing three, four, or five people sitting on the electric scooter and it is running properly, which is a very big risk for the electric scooter as the controller is allowing the motor to operate at a certain load for which the current is drawn from the battery. If the limit is not set properly, the scooter is overloading the motor and its battery is also discharged at a certain current, so the life of the motor and battery are compromised.

Another important parameter is the short circuit. What percentage of load is considered a short circuit in an electric vehicle, say 200 percent or 300 percent, and what happens if the short circuit occurs?

Does the battery give power after how much current you take from the battery and how much load is applied to the motor where it can take that much load?

This is a very important parameter to check as the scooter can go into the water or there could be any other eventuality, so how much time does the controller take to shut down the system so that any eventuality can be stopped in milliseconds?

Every lithium battery bank has its own BMS which defines the overload and short circuit threshold limits, so those threshold limits need to be checked. Every controller also has the same threshold limits as overload and short circuit capacity tests, so generally, they are not synchronized and that creates a lot of issues in the long run. 

So, in the case of a battery bank’s BMS going bad and doesn’t have control over the battery bank, the controller has a different set of overload and short circuit tests. In that case, the battery will keep getting discharged at that particular threshold and a few cells will be damaged and the user will not come to know. To understand this feature practically, we need to understand how the overload will give warning and control the circuitry.

If the user drives the scooter at a particular speed like 100km/h or whatever is specified by the manufacturer’s manual, then in case of overload happens, the speed will be reduced automatically in the scooter. That’s the threshold limit of overload and the controller is designed in such a fashion that in case of overload it gives the warning and if the user doesn’t reduce the speed at a particular time, the overload function kicks in and automatically reduces the speed so that the motor and battery can be saved.

Because when you are using the motor beyond its capacity, the motor might fail, and to drive that motor you are drawing more current from the battery, which will reduce the battery life as well. So this feature operates like this.

Another concept is breaking, so in this case, we need to note down the timing of breaks and the current taken through the controller becomes zero. This process takes how much time? As the controller needs to check when it gets the break signal, how much time does it take to cut off the current? It starts reducing the current and at last stops the top current completely, but if you remove the breaks, it starts again, so the timing between the different times of breaking is very important to check which is the function of the controller.

Another factor is to check the efficiency of the controller, battery bank, and motor. Each of these components has its efficiency at different load factors. So at each load, say 10% to 100% load, we need to see the efficiency of these components. which defines the mileage speed and life of the electric vehicle. Another factor is no load status, which means when the scooter is on but not running, how much current it’s drawing from the battery. So that defines the efficiency of the motor and controller when no load is present, which is called idle current. Some controllers draw very high currents in that status, which will reduce the mileage of the electric scooter as it has a lower efficiency in the no-load status.

For battery testing parameters, it is to check the low battery reserve setting. As this will define the battery life, if the battery reserve is set by the BMS or controller at a lower level than the specified limit, you will get more mileage but the life of the battery will be affected. As the battery reserve needs to be kept at say 48V DC, the system should be around 44V, which will keep the battery life to the maximum. But if the EV manufacturer keeps this to 40 volts, the user will get higher mileage but the battery may go to deep discharge as well, for which the user has to go to special charging of the battery.

If the manufacturer keeps the low battery level at a higher level than the battery reserve, the life of the battery will go up drastically, but in the competitive world, everyone would like to judge the EV on the basis of mileage rather than other parameters. In the automobile industry, so far, mileage and torque are very important, but the comparison is different as the engine is being used. In the EV, the combination of motor and battery is present and to balance, both things are the most important parameter to watch.

If we overload the engine, the RPM automatically reduces to reduce the speed, but in an electric vehicle, everything is minutely controlled, like we can decrease the torque time, and in one minute we can increase the speed of the vehicle much faster than the mechanical engineering and no comparison can be made. As we are drawing the current from the battery, which can be very fast, and it depends upon the speed of the motor, which is again a mechanical part controlled electrically.

The motor specifications are also very important to check whether the motor is performing its parameters.

Generally, the motors used in electric scooters and 3-wheelers are BLDC motors, which have a capacity in terms of watts, generally 250 watts to 2,000 watts and higher. The faster the wattage, the more current it will draw from the battery, so the same size of battery will give more mileage if the wattage is less. because the motor’s consumption will increase with the size of the motor.

Another important aspect is the peak power of the motor, which is required to use in cases of climbing, fast driving, or off-roading. The climbing is for a few seconds or minutes or driving faster for a few minutes, so if that continues for a longer period, the motor gets heated and can be damaged. So this is taken care of by the controller as it has the feature that if the higher current is drawn from the battery for a rated time, then it reduces the current so it automatically speeds slower down than it can take that much more load. Another important parameter is the RPM of the motor, which is called Rotation Per Minute. The higher the RPM, the higher the wattage drawn from the battery. So, if you drive the motor at a fast speed, the current drawn from the battery will be higher. The motor voltage is also specified, such as 48V or 60V, which is used in electric scooters and three-wheelers. The higher the voltage, the lower the current drawn, but the wattage remains the same. So a 48V BLDC motor will take 20.83 Amps of current to give 1,000W of output and the same 60V BLDC motor will take 16.66 Amps of current, but the major difference will be that the efficiency of the motor will increase if it is working on 60V compared to 48V DC, and the life of the motor will increase and wear and tear will also be less in comparison to a 48V DC motor.

All the features of the electric scooter and three-wheeler can be tested by using various testing equipment. To learn more about the Automatic Testing Setup system by Suvastika. Su-vastika’s focus is on designing the Automatic Testing Equipment for testing Electric Vehicles so that we are able to help the Electric Vehicle Industry to test all the parameters to ensure the reliability of Electric Vehicles.

 

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Company Name: Su-vastika Systems Private Limited
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City: Gurugram
Country: India
Website: linktr.ee/suvastika

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