Electric vehicle endurance is not allowed to be a common thing, in the temperature is suitable and gentle to open the words, basically 20% off, once running high-speed or cold winter air conditioning, 60% off, 50% off is also commonplace.
In fact, the energy consumption and mileage of electric vehicles will be affected by the comprehensive influence of temperature, load, slope, driving habits, road conditions and many other factors, coupled with the uneven level of the vehicle's battery management system, it is inevitable that the actual endurance of the vehicle and the calibration data will be different.
From October 1, 2021, most new energy vehicles have replaced the original NEDC (New European Driving Cycle) operating range with CLTC (China light-duty vehicle test cycle) comprehensive operating range.
On October 8, the Model 3 Performance model on Tesla's official website showed a range that changed from the previous 605km to 675km, while the battery capacity of the new model (78.4kWh) was only 1.6kWh more than that of the old model (76.8kWh), and the reason why the mileage was improved was entirely due to the fact that its NEDC endurance standard was replaced by the CLTC working life standard.
At the subsequent Guangzhou Auto Show, all-electric new models released by major brands began to promote CLTC working range, such as cadillac LYRIQ CLTC under working conditions of more than 650km; salon mecha dragon CLTC cruising range of 802km; BMW iX xDrive 50 models up to 665km under CLTC standards; AION LX Plus CLTC comprehensive cruising range of 1008km; Audi Q5 e-tron CLTC has a maximum range of 560 km; ford Mustang Mach-E long-endurance rear-drive SE version, CLTC cruising range of 619 km.
The same model, almost the same hardware parameters, only modified to CLTC conditions, the mileage has been greatly improved, which undoubtedly makes the design for the actual situation in China, instead of NEDC conditions or WLTP conditions, and as the new national standard of electric vehicles CLTC comprehensive working conditions are questioned.
Outdated NEDC conditions
NEDC is an abbreviation for New European Driving Cycle. This set of test standards dates back to the ECE-15 standard in the 1970s, and the latest revision was made in 1997, which is a bit old. In the era of fuel vehicles, NEDC's fuel consumption standards are already notoriously inaccurate.
Mainland China after 2003 on the standard of motor vehicle emission test has been drawing on THEDC, after 2019, the endurance test of electric vehicles also began to use NEDC working condition test, although the mileage is stronger than the previous constant speed range, but because the working conditions are not designed for electric vehicles, it is far from the actual mileage.
This test cycle standard mainly refers to the typical road environment in Europe, including 4 urban cycles and a suburban/high-speed cycle, with a driving distance of 11 km and a total time of 1180 seconds.
The maximum speed of the urban working condition cycle test is 50 km / h, the average speed is 18.77 km / h during the test to accelerate, maintain speed, decelerate, stop, repeated four times, each cycle time is 195 seconds, a total of 780 seconds, driving 1.013 km, the maximum acceleration is 1.042 m / s, the average acceleration is 0.599 m / s.
In the suburban/high-speed test, the car simulates a section of acceleration from stationary to 60km/h, after which it is evenly accelerated and decelerated, driving at a uniform speed of 50km/h, 60km/h, 100km/h and 120km/h, respectively, with a maximum speed of 120km/h, an average speed of 62.6km/h, an effective driving time of 400 seconds, a total of 6.955km, a maximum acceleration of 0.833m/s, and an average acceleration of 0.354m/s. These tests are performed in the laboratory.
In the actual test, the vehicle will be in an enclosed space, the test temperature is between 20-30 ° C, it is fixed on the drum bench, and the motor driven by the drum in contact with the tire is used to simulate the resistance under different working conditions, and the wind resistance is simulated by the fan and the motor, and the non-driving load such as air conditioning, headlights, audio, heated seats and other equipment will be turned off.
NEDC cycle working conditions are characterized by short test time, small mileage, low speed, less variable speed, basically do not consider the impact of ambient temperature on energy consumption, nor fully consider the situation of vehicles constantly starting and stopping when traffic jams in urban areas, suburban / high-speed conditions are accelerated and uniform speed test, so that the core components of the vehicle can maintain a good working state, and the daily driving encountered frequent start stop, big foot throttle overtaking and other working conditions are completely incompatible.
In addition, from the beginning of its birth to its last update of the standard, the NEDC working conditions standard has not considered new energy vehicles that are completely different from the structure and working conditions of traditional fuel vehicles. This is why the ENDurance of THE NEDC will be quite different from the actual endurance, especially in the case of turning on the air conditioner in the summer and the heating in the winter.
More in line with the actual WLTC operating conditions
The WLTC cycle is part of the WLTP (Worldwide Harmonised Light Vehicles Test Procedure), which refers to the typical road environment in many parts of the world, has transient characteristics, and is more in line with the actual driving conditions of the road.
It is suitable for passenger vehicles such as internal combustion engines, hybrid engines, and electric vehicles, and obtains various parameters such as pollutant emissions, carbon dioxide, fuel consumption, and electricity consumption.
Since 2009, led by the United Nations Economic Commission for Europe (UNECE), jointly studied by many experts from Europe, the United States, Japan and other countries, the WLTP test procedure was officially compiled in 2015, and was recognized by the European Union, China, Japan, and the United States. China is also one of the signatory countries, and on July 1, 2021, the WLTP test standard for fuel vehicles and plug-in hybrid vehicles was officially implemented as the basis for the national VI emission test.
WLTC test first according to the power-to-mass ratio classification of vehicles ≤ 22, 22-34 and ≥34 standards, the development of Class 1, 2, 3 three sets of test curves, electric passenger cars are basically tested according to the largest power-to-weight ratio Class 3 standard.
The bench test of the WLTC cycle is divided into four parts: medium and low speed, medium speed, high speed and ultra high speed, with a duration of 589 seconds, 433 seconds, 455 seconds and 323 seconds, respectively, and the corresponding maximum speeds are 56.5km/h, 76.6km, 97.4km, and 131.3km/h, respectively. Acceleration, deceleration, uniform speed, idle speed accounted for about 30%, 27%, 28%, 12%. The number of acceleration and deceleration has reached more than 50 times, and frequent acceleration and deceleration has also increased the difficulty of the vehicle to achieve excellent results.
Compared with the NEDC, the WLTC test time was extended to 1800 seconds; the speed curve variation was more diverse, the average speed was increased to 46.5 km/h, the maximum speed reached 131.3 km/h, and the test distance was 23.25 km, which was twice that of the NEDC test.
WLTC test cycle time is longer, the impact of cold start on the entire test process has been reduced, but also considered the rolling resistance of the vehicle, gear, weight (cargo, passengers), brakes, short stops, etc., the proportion of idle test has dropped significantly, and even the temperature that has a large impact on the battery is also taken into account, and the in-car appliances that were not involved in the test in the past are also included.
For power consumption tests, the vehicle battery must be fully charged when it starts testing on a bench test. Immediately after the test, the engineer reconnected the vehicle to the charger. The connection cable is equipped with a ammeter that can detect the energy loss of the battery during charging. As a result, the tested range is closer to real-world use, and the energy consumption test results of electric vehicles will be 26%-30% worse than that of NEDC.
In the WLTP test process, in addition to the WLTC cycle, the RDE (Real Driving Emissions) cycle is also added as a supplement, including 34% urban, 33% rural and 33% highway driving cycle, covering 90% of the road conditions and temperature, altitude, load, slope, wind direction and many other environmental factors, which is quite close to the actual driving conditions. During the test, the vehicle will travel for 90-120 minutes and reach a maximum speed of 145km/h.
Although optimized for the problem of NEDC operating conditions, this does not mean that the WLTP test is completely in line with the actual situation, it still has a certain deviation. For example, the low-speed working load is low and the change is not drastic enough, the proportion of low-speed working conditions is still small, although the acceleration and deceleration are more frequent, it looks very close to the consumer car situation, but the acceleration process is too long (such as the stationary speed to increase the speed to 45km/h takes 25 seconds), still can not accurately simulate the real scene of the consumer's daily car.
The most demanding EPA conditions
EPA is an abbreviation of the U.S. Environmental Protection Agency, the official name of the EPA Cycle Test Specification FTP-75 (Federal Test Procedure 75), is a test procedure developed by the U.S. Environmental Protection Agency to measure the exhaust emissions and fuel economy of passenger cars with internal combustion engines and the range of electric vehicles, mainly referring to the typical road environment in the United States.
The EPA test includes urban conditions, high-speed conditions, intense driving conditions, air conditioning conditions and low temperature operating conditions, and later for the reproduction of electric vehicles, a test standard for electric vehicles was added, that is, 1 gallon of gasoline equals 33.705 kWh (kWh) standard.
Testing in urban conditions (UDDS) including cold start transition phase (505 sec), steady state phase (506-1372 sec), hot immersion (min. 540 s, max. 660 sec),hot start transition phase (0-505 sec). The entire test lasted 1877 seconds, traveled a total of 17.77km, with an average speed of 34.12km/h and a maximum speed of 91.25km/h.
The high-speed operating condition (HWFET) test used a preheated engine and did not stop, the driving distance was 16.45 km, the average speed was 77.7 km/h, the top speed was 97 km/h, and the total duration was 765 seconds. The road condition test is run twice, with a maximum interval of 17 seconds. The first run is vehicle pretreatment, and the second run is actual testing and emission measurements.
The intense driving condition (US06) first conducts a high-speed, high-acceleration test, pre-treats the vehicle to warm up the vehicle, then idles for 60-120 seconds, and then directly enters the high-speed, high-acceleration driving cycle to start the formal test. The driving distance is 12.8 km, the average speed is 77.9 km/h, the maximum speed is 129.2 km/h, and the duration is 596 seconds.
The air conditioning service condition (SC03) is to show the engine load and emissions associated with the use of air conditioning units in the summer heat. The laboratory temperature is 35 °C, the relative humidity is 40%, and the air conditioner is always turned on at the maximum cooling capacity during the test. The vehicle is pre-treated under this operating condition first, then the engine is turned off and hot-dipped in the environment for 540-660 seconds and then hot started to start the formal test. The test distance is 5.8 km, the average speed is 34.8 km/h, the maximum speed is 88.2 km/h, and the duration is 596 seconds.
There is also a cold operating condition (Cold UDDS), the test process is consistent with the city conditions, but the temperature is adjusted from the normal 25 ° C (between 20 ° C - 30 ° C) to -7 ° C for testing. The measured results are calculated by different proportions of various cycles.
For plug-in hybrids and pure electric vehicles, EPA began in 2010, using the "MPGe energy equivalent method" to convert the energy consumption of electric vehicles into miles traveled per gallon, calculated as 33.705kWh is equivalent to 1 gallon (gallon) gasoline, and 1 gallon is equal to about 3.785L, so this also makes the EPA test results closer to the actual car situation. The larger the value of MPGe, the lower the equivalent energy consumption.
When the EPA tests the electric vehicle, first of all, the car should be completely drained, the vehicle will be fully charged before the test, then it will be left overnight, and the next day the test will repeat different cycles such as urban conditions and high-speed conditions until the car is not enough to support it to complete the entire cycle. After the end, the car is fully charged again, and the actual mileage and power consumption value are measured.
In general, compared with other test standards, the EPA test standard is longer, the mileage is long, the speed is high, the speed is more variable, and the impact of ambient temperature on energy consumption is considered, these test items are highly similar to the daily car habits of North American drivers, but this use method is very unfavorable for new energy electric vehicles with faster speed and higher power consumption. Relatively speaking, EPA is the closest test standard to the actual fuel consumption of fuel vehicles and the actual mileage of electric vehicles.
However, because the EPA is based on the road conditions in the United States, the test is complex, the cost is high, the implementation is difficult, and it may adversely affect the automotive industry, so the mainland has not adopted the test condition standard.
If you are driving a Tesla, because the Tesla car and machine system is displayed in accordance with the EPA working conditions standard, the actual mileage of driving is not more than 10% of the standard error with the EPA, which can be used as a more accurate reference.
CLTC conditions tailored to China
From the above-mentioned cycle standards of various working conditions, there are obvious differences in parameters such as average speed, average acceleration, average deceleration, acceleration ratio, deceleration ratio, uniform speed ratio, and idle ratio.
These differences stem from which countries, cities, or regions the standard-setters collect data from when they develop standards. The national conditions are different from country to country, and there are also differences between different cities.
In january 2015, the Ministry of Industry and Information Technology (MIIT) issued a research task for China's automotive testing cycle CATC (China Automotive Testing Cycle) in order to bring fuel consumption test data closer to the real situation on China's roads.
In 2016, this task was led by China Automobile Research Institute and promoted by industry experts, which lasted for three years and supported a total of 92.4 million yuan. The project mainly selected 41 representative cities, collected data for 5,048 vehicles of various types, collected about 55 million km of vehicle data, and 2.1 billion pieces of low-frequency traffic big data, covering urban areas, suburbs, main roads, expressways and highways, and covered four seasons, weekdays, holidays, peaks and peaks.
The project team also determined the scope of acquisition parameters, involving a total of 22 parameters in five categories, including vehicle GPS, engine powertrain, new energy vehicle battery motor, environmental information and vehicle emissions. The information collected includes vehicle location information, power drive system information, battery information, emissions and environmental information.
After actual collection, the average speed of China's working conditions (29km/h) is 58.6% different from WLTC (46.5km/h), the idle ratio of Chinese working conditions (22%) and WLC (13%) is 40%, and the proportion of speed time above 80km/h is 77%.
On February 23, 2021, the Ministry of Industry and Information Technology released the mandatory national standard "Fuel Consumption Limit for Passenger Cars" on its official website, which is actually CATC. CATC has designed CLTC-P, CLTC-C, CHTC-B, CHTC-C and other 8 working conditions for different types of vehicles. We usually say that the CLTC condition is part of the CATC, usually referring to the light passenger vehicle condition (CLTC-P).
On July 1, 2021, the test conditions for conventional energy passenger cars and plug-in hybrid electric passenger cars will be switched from NEDC to WLTC. From October 1, 2021, pure electric passenger cars and fuel cell passenger cars will directly use CLTC conditions. After 2025, the WLC standard for fuel consumption testing will also be replaced by the constantly improving CLTC standard.
The cumulative driving mileage of CLTC-P for passenger cars is 14.48km, including low-speed, medium-speed and high-speed conditions, which match the urban, suburban and high-speed conditions of consumers' daily driving.
The working condition is 1800 seconds, the low-speed working condition is 674 seconds, the time ratio is 37.4%, the medium speed working condition is 693 seconds, the time ratio is 38.5%, the high-speed working condition is 433 seconds, the time ratio is 24.1%, the average speed during the period is 28.96km/h, the maximum speed of high-speed condition is 114km/h, and the idle (stop) time is 22.11%.
ClTC conditions seem to be more suitable for mainland car driving conditions, but it is precisely this plausible setting that results in a higher CLTC service range than NEDC service range.
First of all, the test weight of the CLTC working life standard is significantly more biased towards the performance of medium and low speeds than the NEDC working life standard and the WLTC working life standard.
The maximum speed set by CLTC is lower than the 120km/h of the NEDC and WLTC service endurance standards, and the average speed is 28.96km/h, which is lower than the NEDC and WLTP cycle conditions.
Second, the CLTC operating condition test has a longer idle time. The ID time in clTC test is up to 23.33%/419 seconds, while in THE NEDC condition, the idle ratio is 24.93%/284 seconds, and under WLTP conditions, the idle ratio is 13.06%/235 seconds. Idling does not increase power consumption, which is more beneficial for extending the range of electric vehicles.
Third, clTC working conditions are biased towards frequent acceleration and deceleration, acceleration is greater than NEDC working conditions, in line with the actual domestic stop-and-go road conditions, and more frequent acceleration and deceleration conditions, for electric vehicles with higher efficiency and kinetic energy recovery, it is very conducive to improving the mileage.
Fourth, the current CLTC test conditions are carried out without air conditioning, and actual people driving in hot or cold climates definitely need to use air conditioning. The use of ambient temperature and air conditioning system has a greater impact on the mileage, and the test did not take into account, so the difference in mileage was increased.
These situations can be seen that the CLTC endurance standard overemphasizes the city-based passenger car driving conditions, ignoring the huge energy consumption loss of electric vehicles driving in different environments, and the consequence is that the whole vehicle in the test is always running in a mode of high recovery rate and low power consumption demand, resulting in the mileage obtained by the test even exceeding the NEDC working condition endurance standard and the WLTC service life standard.
CLTC's working condition setting is mainly based on a large amount of data collected by the traffic GIS from 2016 to 2018 on the road of Chinese cars. In 2018, the penetration rate of new energy vehicles in the mainland was only 4.54%, and the number of new energy vehicles in the country reached 2.61 million, accounting for 1.09% of the total number of vehicles; and at that time, the mileage of pure electric vehicles was basically about 300km, which was more suitable for low- and medium-speed urban conditions.
CLTC working condition test of the mileage of the false standard, convenient for manufacturers to carry out publicity, is conducive to the promotion of new energy vehicles and may form greater confusion for users, and even form a mileage estimate of misleading, causing unnecessary trouble.
With the advancement of the double carbon target in the past two years, the technical level has been greatly improved, new energy vehicles have shifted from policy-oriented to market-oriented, and the number of new energy vehicles on China's roads has increased sharply, and by the end of 2021, the number of new energy vehicles in the country will reach 7.84 million, accounting for 2.60% of the total number of vehicles.
According to the data of the Federation of Passenger Vehicles, the output of new energy passenger vehicles in March 2022 was 437,000 units, an increase of 124.2% year-on-year, and the domestic retail penetration rate was as high as 28.2%, compared with the basic formation of clTC test standards in 2019 (the penetration rate of new energy vehicles was only 5.0%), an increase of nearly 6 times, has become an important force in the rapid rise of China's automobile market, and the current traffic road situation is also very different from when CLTC was formulated.
In different climatic conditions, more and more owners choose new energy vehicles as the main means of transportation, the driving range and mileage demand of electric vehicles are constantly expanding, in the current new energy vehicles, especially electric vehicles, the long time to replenish energy, the network is not wide enough, mileage anxiety has become the main pain point of new energy vehicle users, and accurately reflect the actual mileage of the vehicle has also become a need for electric vehicle drivers to pay more and more attention.
Fortunately, according to the planning of the Ministry of Industry and Information Technology, clTC standards will be fully applied to the automotive industry in 2025. Previously, the relevant national management departments and institutions will certainly continue to update and optimize the CLTC working condition test, such as increasing the experiment of turning on the air conditioner at high and low temperatures (high temperature 30±2 °C, low temperature -7±3 °C), increasing the investigation of the level of braking energy feedback, so as to be more in line with the actual use of the car, more objectively reflect the energy consumption of pure electric vehicles, and more truly evaluate the energy consumption and mileage of pure electric vehicles.
We expect that the CLTC working condition test can be more scientific and comprehensive before it is fully implemented, so as to obtain mileage estimates that are closer to the actual situation and eliminate people's mileage anxiety.