For electric vehicles, range has always been one of the most concerned issues, so how do we make sure that our car has enough charge to reach the next charging station?
There are currently three international standards for electric vehicle range testing, namely EPA in the United States, NEDC in Europe, and WLTP in the United Nations. Which test method is more reliable and closer to the actual range? In general, it is EPA > WLTP > NEDC.
NEDC
The full name of the NEDC is the “New European Driving Cycle”, which is the current standard used in European driving tests. In addition to Europe, this standard has also been used in China and Australia.
The NEDC test method mainly consists of 4 urban cycles and 1 suburban cycle.
Simply put, it is to let the vehicle run from full charge according to the above NEDC speed cycle until the power runs out, and the driver’s requirement is that the speed deviation does not exceed 2km/h.
So, how does it work?
The first thing to tell you is that whether it is the endurance power consumption of the new energy vehicle or the fuel consumption of the traditional car is tested on the “treadmill”, the scientific name of the “treadmill” is chassis dynamometer, commonly known as the drum. The car is stationary on the drum, and only the wheels are rotating with the drum when accelerating, so the energy consumption measured in this condition is not a big bargain? In fact, it is not, the front and back of the two barrels will be connected to a dynamometer, the dynamometer can not only measure the power output of the wheel, but also actively generate opposite forces on the wheel to simulate the resistance of the vehicle.
After the dynamometer gets the sliding resistance, it can begin to carry out the endurance test, which mainly includes the following steps:
1.Charge and dip the car
Charging: Charge at a laboratory temperature of 20-30℃;
Soak the car: After full charge, soak the car at the laboratory temperature of 20-30℃ for at least 6h.
2.Formal test
A long cycle test is carried out in accordance with the NEDC working condition until the accelerator speed does not meet the tolerance requirements under the NEDC working condition. At this time, the driver releases the accelerator, does not step on the brake, coastes to the stop, records the vehicle mileage De (Km), and rounds to an integer.
3. Power consumption calculation
After the test, the vehicle was connected to the power grid for charging within 2h, and the energy from the power grid was measured, which was divided by the driving distance measured the previous day to obtain the power consumption of the vehicle, in kWh/100km.
60km/h constant speed method
The above introduces the NEDC mode test, the uniform speed method test is relatively simpler, of course, but also more ideal, the actual mileage shrinkage is larger, once criticized by consumers. The main process is that the vehicle carries out a constant speed test of (60±2) km/h, and calculates the driving distance and energy consumption rate at constant speed according to the driving distance and energy consumption.
Car companies generally announce the driving mileage tested by the above two methods, the general constant speed method driving mileage is about 20% more than the driving mileage under NEDC conditions, because the test conditions are too idealized, the current car companies and consumers pay more attention to the driving mileage under NEDC comprehensive conditions.
Through the above introduction, I believe that everyone has a preliminary understanding of the test method of electric vehicle driving range, then some people will ask what factors affect driving range? Why is it frequently claimed that the NEDC has a comprehensive range of 500km, but the actual driving down is only 300km? So, is the driving range of the NEDC test accurate?
Let’s talk about the specific factors that affect our driving range.
1.Environmental factors
The NEDC cycle test simulates the ambient temperature of 25 ° C, and accessories including headlights and air conditioners that can generally be turned off will be turned off to save electricity, but in actual driving, headlights and air conditioners will inevitably be turned on, such as night driving, headlights will probably consume dozens of watts of power, which will increase your energy consumption by 1 to 2%. The consumption of air conditioning in winter and summer is even worse, the general air conditioning power is 1-2kw, and it can reach 3kw at very low temperatures. Assuming that the electric vehicle consumes 15kwh for 100 kilometers, according to the air conditioning power of 2kw, the driving distance of about 5h will be reduced by close to 70km because of air conditioning; Another algorithm, the average net power of a car in the NEDC working condition is probably less than 5kW, so if the air conditioning consumes 2kW, the driving range will decrease by 30%. In this way, the main reason for the decline of electric vehicle driving range in winter is not the battery decay that we think, but the consumption of air conditioning.
2.Driving condition factors
Because of the relationship between wind resistance, the driving resistance of the vehicle with the speed can be considered to be a quadratic curve relationship, in popular terms, that is, every time the speed rises a little, the motor has to consume some additional energy to overcome the resistance, which is why the higher the speed, the greater the power consumption of 100 kilometers.
Because of the relationship between wind resistance, the driving resistance of the vehicle with the speed can be considered to be a quadratic curve relationship, in popular terms, that is, every time the speed rises a little, the motor has to consume some additional energy to overcome the resistance, which is why the higher the speed, the greater the power consumption of 100 kilometers. For example, suppose that the resistance curve of a car is:
∑ F = 120 + 0.5 x v ∗ + 0.03 v
Without considering the driving efficiency, it can be obtained by simple calculation that the energy consumption of the car at several typical speeds of 100 kilometers is as follows:
Speed km/h 100km Energy consumption kWh/100km
| Vehicle speed km/h | Energy consumption kWh/100km |
| 60 | 7.2 |
| 80 | 9.8 |
| 120 | 17.0 |
Although the above calculation is not rigorous, it can also be clearly seen that the same 100km distance is run, with the increase of the driving speed, the power consumption will increase rapidly. In general, high-speed driving will be 20-30% lower than the standard driving range, SUV due to the windward area is larger, the loss will be more serious.
3.Resistance factors
Finally, the problem of resistance, NEDC comprehensive driving mileage is tested on the chassis dynamometer, and the resistance coefficient provided to the dynamometer is obtained by sliding on a good road, and our actual driving conditions are diverse, there are potholes on the road, speed bumps or water in the rain, will lead to increased actual road resistance; In addition, the NEDC test according to the loading standard 100kg, equivalent to an adult plus some luggage, and the actual driving is likely to take more than 2 people, the increase in vehicle load will also lead to increased resistance, each more than one person will probably make your energy consumption increase by 3~5%, driving mileage reduction is also reasonable.
The purpose of explaining the above factors is not to attack how inaccurate the driving mileage results measured by the standard NEDC are, after all, each manufacturer must unify the standard, there is a unified standard, and everyone’s level is comparable. What I want to tell you here is that under different circumstances, each factor has an impact on driving mileage, so that you can make a judgment on the real driving mileage according to the actual situation before traveling, and develop good driving habits, which is also of great benefit to the increase of driving mileage.
For a developed car, the driving range is mainly affected by the above factors, but from the source, the vehicle factory also needs to continuously optimize the motor battery efficiency, improve energy density, reduce vehicle resistance factors, etc., to effectively improve the driving range.
In fact, when choosing new energy electric vehicles, you can multiply the range of the NEDC standard by 0.7~0.75 to roughly estimate the actual driving range. At the same time, it is also important to pay attention to the results of other test criteria to get a more complete picture of the car’s endurance. In this way, we can make more intelligent car purchase decisions and choose new energy electric vehicles that are really suitable for us.