The endurance performance of pure electric vehicles at low temperatures is related to a variety of factors, and it is not accurately tested by fully charging the vehicle in a low temperature environment and then running the nest.
I believe that all friends who eat instant noodles for the first time have been deceived by the pattern on the outer packaging. A bowl full of beef is displayed, and after cooking, there are only a few beef grains. This incident made us know the importance of correctly understanding the "pictures for reference only". The same is true for the endurance test of electric vehicles.
Every winter, we can see all kinds of data on the winter endurance test and endurance test of pure electric vehicles from the network. Although it is winter, although the temperature is lower than one, although the whole process can be broadcast live to ensure the authenticity of the data, what EV Jun wants to say is that these data are separated from the test of the actual use scenario of the user, and the reference is almost the same as the packaging and physical objects of instant noodles. Why? Let's talk about it bit by bit.
Temperature determines endurance Low temperature but not as low
The number of winter mileage of pure electric vehicles is closely related to the temperature. Although we see all winter low temperature tests, when you understand the characteristics of the battery, you will find that it is also low temperature, but there is a very large gap between the battery at zero, 0 degrees and -10 degrees Celsius.
The picture above is a usable capacity test of the 80 Ah lithium-ion battery with a nominal voltage of 3.7V at different temperatures. The same batteries are placed in temperature chambers at 25, 0, -10, -20, -30 and -40 °C for discharge experiments, and the batteries are discharged after 5 hours of standing.
The results have shown that the available power of the battery also changes significantly as the temperature changes. Taking -10 degrees Celsius as an example, the usable power of the battery has been reduced by 12.5%, at -20 ° C, the battery capacity is reduced by 21.2%, and at -30 ° C, the battery capacity is reduced by 46%.
The reduction in battery capacity (what we usually call the attenuation of the battery due to low temperatures) also means that the range of the vehicle has been reduced without the use of any electrical equipment. Taking a model with a range of 500 km as an example, at -10 degrees Celsius, the endurance has been attenuated by 12.5% to about 430 km, and at -20 ° C, the endurance has been reduced by 21.2% to less than 400 km.
From the above data, we can see that although the network shows the results of the low-temperature endurance test, although the temperature at the beginning of the test is explained (generally the temperature is lower in the morning to start the test), these data are basically fully charged to use a day's time to drive the vehicle at least to the nest, and the temperature changes greatly within one day, so the final data can only play the meaning of "reference only".
The test process seriously violates the user's normal car logic
As we have already mentioned above, then most of the results of the winter low temperature and cold test of pure electric vehicles that we see on the Internet are the results obtained after a full charge and a single start directly drives the vehicle to the nest, but what EV Jun wants to say here is that this test method can only reflect the endurance performance that the driver of the online car can run out of using the pure electric vehicle, which is completely inconsistent with many consumer car scenarios.
Pure electric vehicles are different from fuel vehicles, in the winter in addition to the battery itself due to low temperature caused by the reduction of capacity, the electrical equipment on our car also has a very serious impact on the endurance. At present, pure electric vehicles have a battery heating system, when we start the vehicle in a low temperature environment, the battery heating system will also start to heat our entire battery pack, at this time, the liquid required for heating is cold, the battery is also cold, just start the vehicle battery heating after opening is often more expensive than steady-state heating in the process of driving later.
So how much does heating affect battery life? We have also tested both states before. From the data of the above two figures, it can be seen that the vehicle starts to show a battery life of 442 kilometers, and after driving for 1 kilometer in 5 minutes under congested road conditions after just starting, the remaining endurance is 437 kilometers, directly falling 5 kilometers.
After 14 minutes of driving 4.7 kilometers, the endurance dropped 12 kilometers, with the smooth flow of the road, the battery temperature gradually increased, the actual endurance and the table endurance drop gradually approached, in simple terms, the initial heating system work is particularly expensive, but with the gradual increase in the battery temperature during the driving process, but also through the driving process of the discharge after heating up, the endurance becomes more and more solid.
Through this test, we can see that after a car is fully charged until the next charge, the number of cold starts determines the length of the endurance test range. In the process of our daily use of the car, almost no one will fill the car every day and then run the vehicle to the nest at one time, basically driving to work in the morning and driving off work at night, which also includes two cold starts. And when fully charged until the next charge there will be multiple cold starts, then the final mileage of the vehicle will be shorter than the mileage of a single cold start until the vehicle is nested. And in theory, the more cold starts, the shorter the endurance.
Through this information, we can know that the results of those winter endurance tests on the network, although they are closely related to the low temperature and the actual use scenarios of users, but the final results can only be said to be the farthest endurance that pure electric vehicles can run out of in winter, if you are normal commuting, it will not exceed this endurance, and its data can really only be "for reference only".
The results of the test just after a full charge are even more outrageous
In addition to the above problems, there is also a test process that is not rigorous, which also leads to the "referentiality" of the final continuation data test, that is, the test process just after the full charge, when we see these data tests, we must understand that such test data is only for the home charging pile, or even the fast charging pile, and the vehicle is also just full when driving in the morning.
Why is it so, mainly when our vehicle has just been fully charged, because the battery has a large current input battery will heat up on its own, and the battery heating system has been fully heated during the charging process. According to the different strategies of manufacturers, the heating temperature is also different, but most models of heated battery temperature is basically around 25 degrees Celsius, and this temperature is exactly the best performance of lithium batteries, compared with the nominal capacity, there is almost no capacity attenuation caused by temperature.
In addition, the start of the test vehicle endurance in this state also eliminates the power consumed by battery heating, the whole process is completely inconsistent with the user's use scenario, and the winter endurance tested in this way must be the longest. But as a consumer, you can hardly achieve such a battery life when you actually use it.
summary:
The endurance performance of pure electric vehicles at low temperatures is related to a variety of factors, and it is not possible to test the vehicle by filling the running nest in a low temperature environment, which has a great relationship with the degree of vehicle newness and oldness (the battery will gradually decay with the vehicle driving) The temperature in which the battery is located, the heating power under the warm air and the heating power under the different temperatures of the battery heating system.
If you want more consumers to accurately understand the winter low-temperature endurance performance of the vehicle you want to buy, you also need the relevant government agencies to give specific test standards, and you also need the car companies to continue to make breakthroughs in technology, and strive to accurately display the remaining endurance at different temperatures and different power states of the vehicle, only by reducing the deviation rate of the table endurance and the actual endurance to the minimum can we solve the most fundamental problems. Of course, I also hope that battery technology will progress rapidly, when 1000 km endurance becomes the standard, 10 minutes can be full, no one will care about the endurance of pure electric vehicles, just like no one cares about the endurance of fuel vehicles.