In the case of the increasingly perfect new energy vehicle technology, China's new energy vehicle market has ushered in a round of explosion in the past year. As of November this year, the retail penetration rate of new energy vehicles in China has reached 20.8%. This also means that on average, one of the 5 vehicles sold in China is a new energy vehicle, which is a significant increase compared with the market penetration rate of 5.8% last year. Obviously, new energy vehicles have been further recognized by Chinese consumers.
The reason why new energy vehicles will gradually be recognized by consumers is part of the reason why policy support is part of the reason, and the improvement of pure electric vehicles in terms of endurance allows consumers to have no worries. At present, the endurance of pure electric vehicles can generally reach 500-700km, and car companies such as Weilai, GAC Aean and Zhiji Automobile will also launch an impact on the 1000km endurance mark this year.
Even if new energy vehicles have been able to launch an impact like 1000km endurance, the endurance claimed by car companies has far exceeded that of traditional fuel vehicles, but it still has shortcomings that cannot be ignored. For example, the harsh winter cold will mercilessly tear off the fig leaf of pure electric vehicles in terms of endurance.
Low temperature continuous driving evaluation hit the face of ternary lithium
With the arrival of winter, many media have taken advantage of the cold temperature to do a harsh winter endurance test on pure electric vehicles that are afraid of cold nature. Among them, ByteDance's automotive media platform released the winter test endurance results of 40 electric vehicles in one breath a week ago. The test standard is very stringent, the test site is located in Yakeshi City, Hulunbuir City, Inner Mongolia Autonomous Region, when the temperature of Yakeshi is as low as -20 °C.
Although the car emperor has tested the endurance of pure electric vehicles in extreme temperatures to the greatest extent, the temperature in the northern region of China is mostly below -15 ° C. Therefore, although the winter test results of the car emperor are quite interesting, they are slightly biased from the actual car use scene in China.
On December 24, China Automobile Research Institute (CCRT) released the mileage evaluation results of six pure electric vehicles sold in China's automobile market. Although the models tested by China Automobile Research Institute are not as comprehensive as those that understand the car emperor, they are basically hot models on the market and have certain reference value for consumers who intend to buy new energy vehicles.
The test is tested at room temperature 23 °C and low temperature -7 °C, which can not only verify the difference between the official mileage and the actual mileage, but also verify the degree of attenuation of these new energy vehicles at low temperatures, which is more in line with the car use scenarios of new energy vehicle users in China.
Models participating in this review include Tesla Model 3, NIO EC6 Sport, BYD Han EV, Xiaopeng P7, BMW iX3 and Nezha U Pro 500. Judging from the test results, these six models have a better performance in the normal temperature mileage test, but their low temperature driving range is difficult to say.
Among them, the winter endurance performance of by THE BYDHan EV is the most outstanding, compared with the 629km cruising range measured by the China Automobile Federation at room temperature, its cruising range at low temperatures is 435km, and the decline rate is 30.9%. Nezha U Pro's performance is the worst, compared with the 550km cruising range tested at room temperature, its cruising range at low temperatures is only 232km, and the decline rate is as high as 42.4%.
It is worth mentioning that the models with excellent low temperature endurance performance in this test are basically equipped with lithium iron phosphate batteries. You know, due to the different chemical compositions, winter endurance has always been a place where lithium iron phosphate batteries have been criticized, and the winter performance gap between it and ternary lithium batteries cannot even be bridged.
However, this test is a surprising performance of the ternary lithium battery that originally dominated the winter endurance. So how did a pure electric vehicle equipped with lithium iron phosphate batteries reverse the trend in this test? To analyze this problem, we first need to understand what impact low temperatures will have on the endurance of pure electric vehicles.
Factors affecting the low temperature mileage of trams
The factors affecting the low-temperature driving range of pure electric vehicles mainly include three points, one is the power consumption of air conditioning; second, battery attenuation; third, mechanical loss.
1, heat pump air conditioning to the tram superimposed a heavy BUFF
In terms of air conditioning power consumption, since pure electric vehicles do not have a heat source such as traditional fuel vehicle engines, it cannot solve the heating problem in the car by importing engine heat. In order to solve the heating problem, the current pure electric vehicles mainly adopt PTC and heat pump air conditioning these two technical solutions, but these two technical solutions have their own advantages and disadvantages.
Among them, the working principle of PTC technology is similar to the "hot fast" we used to boil water in the past, and its advantage is that it is low cost, but it is extremely power-consuming.
Generally speaking, the power value of pure electric vehicles in urban areas is about 3kW, when the temperature drops below 0 °C, the heating demand power through PTC heating technology will be greater than the power required for urban working conditions; when the temperature drops to -20 °C, the air conditioning heating demand power will exceed 6kW. This means that when pure electric vehicles are below 0 °C, PTC heating consumes more power than the drive motor that drives the wheels.
The heating efficiency of heat pump air conditioners is more than 2.5 times that of PTC technology, and the energy consumption of pure electric vehicles using heat pump air conditioners is 30-40% lower than that of PTC technology. However, the cost of heat pump air conditioning is high, and the cost of a heat pump air conditioner is as high as thousands of yuan, which is not suitable for models with lower positioning.
In fact, the results of the low temperature mileage test of China Automobile Research Institute also verified the importance of heat pump air conditioning. Among the six cars participating in the test, the best performing BYDHan EV and Tesla Model 3 are equipped with lithium iron phosphate batteries, but they are equipped with expensive heat pump air conditioners at any cost.
The worst performers, the Nezha U Pro 500 and Xiaopeng P7, are equipped with inexpensive but extremely power-hungry PTC heating technology. Among them, Nezha U Pro 500 is mainly limited by the price, and the Xiaopeng P7, as the most popular flagship car under Xiaopeng Automobile, is because of the early launch time, so the configuration is somewhat backward.
In Xiao Lei's view, the heat pump air conditioner is the key to the success of Tesla Model 3 and BYD Han EV in this winter endurance test. Although the heat pump air conditioner is not exclusive to the lithium iron phosphate battery model, Xiao Lei does not think that they are suspected of speculation in this victory. On the contrary, they spare no effort to install heat pump air conditioners locally.
As mentioned above, the heat pump air conditioner is not the exclusive configuration of the lithium iron phosphate battery model, Tesla Model 3 and BYD Han EV have made a qualitative breakthrough in winter endurance after being equipped with heat pump air conditioning. In addition to further optimizing the air conditioning technology, it is also particularly important to work on the battery itself.
2, battery heating is the door technology activity
There is an idiom in our country called "worse than worse". In Xiao Lei's view, the word is used just right in the winter endurance of pure electric vehicles. The heating problem of pure electric vehicles is like the "frost" on new energy vehicles, but the more serious problem of pure electric vehicles is not only "frost", but also "snow" itself, and the power battery is afraid of cold is the "snow" of pure electric vehicles.
There are three main factors that affect the performance of pure electric vehicle power batteries in the low temperature environment:
First, battery capacity. Because the electrolyte of the power battery is liquid, the liquid will become viscous or even solidify in the low temperature environment. The viscous electrolyte will cause the internal resistance of the battery to increase, the efficiency will decrease, and the battery capacity will also drop faster. This is the same reason that we swim in clear water is more labor-saving than swimming in the paste.
Second, the battery has the risk of lithium evolution at low temperatures, which is like a long thorn inside the battery, which may damage the battery structure and cause a short circuit inside the battery. To reduce this risk, battery management systems typically limit the maximum allowable charge and discharge power of the battery. After all, compared to charging and endurance, safety should always be put first.
However, it is precisely because the battery management system will limit the discharge power of the power battery in a low temperature environment, which will lead to poor dynamics of the vehicle. Such a situation can easily make pure electric vehicle users have the illusion that the vehicle may run out of power at any time, exacerbating their endurance anxiety.
Third, the difference in the cell of the single battery will pull down the overall performance of the battery pack. Since the battery pack itself will follow the barrel effect, and the current thermal management scheme of pure electric vehicles cannot affect the uniformity of all the single cells in the battery pack, the single battery with the lowest temperature will determine the overall performance of the battery pack.
For example, most of the single batteries in the battery pack have a temperature of about 10 ° C, but there is a single battery that has not been warmed by the thermal management system at a temperature of only 0 ° C, then this low temperature single battery is like a grain of mouse, a bad pot of porridge.
If the heat pump air conditioner solves the problem of people's fear of cold, then the battery heat management system is specifically designed to solve the problem of battery cold. However, the problem of battery cold is not as simple as adding money to the heat pump air conditioner.
The technical solutions for heating the power battery mainly include external heating and internal heating. Internal heating is faster and more efficient than external heating, but also at higher risk. In fact, the field of new energy vehicles has always had a nightmare word - thermal runaway.
It can be seen that the power battery is not unable to generate its own heat, but it is a very challenging and dangerous technology to control the heat of the battery at a controllable temperature. Therefore, internal heating has not become the mainstream technology of current battery thermal management systems.
In order to alleviate the problem of battery cold, the current mainstream solution is to develop an excellent battery thermal management system to heat the power battery through external heat, and such a solution has not been perfect so far. The control logic of external heating is relatively complex, and the timing of heating will directly affect the available capacity of the battery.
Heating at 80% of the battery is very different from heating at 30%, and at what temperature it is activated is also very different for users in different regions. For example, if the heating is activated at 0 degrees Celsius, the heating mechanism of the pure electric vehicle in the north will be activated frequently, while the heating mechanism of the pure electric vehicle in the south may never be activated.
In this regard, Tesla has done a good job, it has played its own vertical integration advantages, making full use of motor waste heat to heat the battery. You know, although pure electric vehicles do not have a high-heat heat source such as engines, high-performance motors can also generate a certain amount of heat.
In addition to the unique disadvantages of pure electric vehicles such as winter heating and battery cold, the mechanical loss of the car itself in winter is also the direction that pure electric vehicles need to optimize.
3, the oil truck is more serious than the tram mechanical loss, but the tram mechanical loss is more urgent
The so-called mechanical loss is the energy loss caused by mechanical components. In fact, compared with pure electric vehicles whose mechanical structure has been greatly simplified, the mechanical losses of traditional fuel vehicles are more serious.
There is a crucial technical parameter in the field of the internal combustion engine called "thermal efficiency". At present, even the BYD Snap Cloud engine, which has achieved the peak thermal efficiency, its thermal efficiency is only about 43%. This means that the internal combustion engine has lost more than 50% of its energy when converting chemical energy into kinetic energy, and the energy that is actually delivered from the crankshaft to the wheel is even more pitiful.
In addition, cars will have more mechanical losses in low temperature environments. Among them, the tires will become harder in the low temperature environment, and the tire pressure will also be reduced, which will increase the rolling resistance of the car. In order to solve this problem, new energy vehicle companies often choose low rolling resistance tires, and car owners can appropriately increase the tire pressure of the car in low temperature weather.
Secondly, the electrolyte of the power battery will increase the internal resistance in the low temperature environment, and the viscosity of the oil between the mechanical parts of the car will naturally change with the change of temperature. The lower the temperature, the thicker the oil becomes, eventually exacerbating the transmission loss, which is a reason for Xiao Lei's example of "swimming" given above.
Again, the air density of -7 °C is 1.12 times that of the ambient air density of 25 °C. It should be known that when the speed of the car is lower than 60km/h, the impact of air resistance on the energy consumption of the car is not large, but as the speed increases, the air resistance will rise rapidly. When the speed reaches 120km/h, 60% of the energy consumption of the car will be used to resist air resistance, which is the main reason why new energy vehicle companies have paid more attention to the wind resistance coefficient in recent years.
However, traditional fuel vehicles do not pay too much attention to mechanical losses, because mechanical losses affect only the fuel consumption and power of a car, but it takes countless time and energy to make these mechanical parts better.
For car companies, a small mechanical loss can become the direction of technology optimization, but it is not the focus of research and development. After the traditional fuel vehicle runs out of fuel, any gas station can be replenished in time, but the direct feeling that the mechanical loss of pure electric vehicles can bring is the anxiety of endurance. Therefore, although the mechanical loss of traditional fuel vehicles is far more serious than that of pure electric vehicles, the mechanical losses of pure electric vehicles are still more urgent than that of traditional fuel vehicles.
The battery faction battle is far from over
If you look at the battery cell technology alone, the current mainstream lithium iron phosphate battery has not been given much of a transformative upgrade. In Xiao Lei's view, the reason why they can counterattack is because the turtle and rabbit race and can make up for it.
You know, energy density has always been the proud advantage of ternary lithium batteries, and safety and cost are its hidden pain points. Therefore, car companies and battery suppliers have become more inclined to stumble on the safety shortcomings of ternary lithium batteries in recent years.
In fact, From 2017 to 2021, China Automobile Research Institute has tested a total of 34 pure electric vehicles. The test results show that the endurance of pure electric vehicles has improved significantly in the past 5 years. In Xiao Lei's view, the endurance of pure electric vehicles has been able to have such an improvement in recent years, and the ternary lithium battery has contributed an indispensable contribution.
It is true that today's pure electric vehicle endurance has basically spanned 450km, and the mainstream pure electric vehicle endurance has even reached 568km, and this year car companies have even begun to challenge the 1000km endurance mark.
However, in the past 5 years, the low-temperature driving range reduction rate of pure electric vehicles is still above 35%, and the average low-temperature mileage reduction rate of the six models tested this time is as high as 39%. It can be seen that compared with the cruising range at room temperature, the low-temperature driving range is still a pain point that is difficult to cure for pure electric vehicles.
Low temperature driving capacity is still room for ternary lithium batteries that have advantages in energy density and cold resistance, but for lithium iron phosphate batteries, it is enough for many consumers in the north to retreat from it.
Xiao Lei believes that it is precisely because the winter endurance of lithium iron phosphate batteries is weak, which has led to car companies and power battery suppliers more inclined to make up for its shortcomings in this regard. This and Xiao Lei said above, ternary lithium battery suppliers know that their shortcomings are safe, so they tend to focus more on making up for safety shortcomings when upgrading products.
It should be known that in order to enhance product strength, any company will give priority to making up for the shortcomings of its own products in the barrel effect when upgrading products, and it is even more important for a new energy vehicle company to make up for the shortcomings in winter battery life.
For example, BYD equipped the Han EV with a heat pump air conditioner that the competitor Model Xiaopeng P7 does not have, so it makes up for the technical shortcomings brought by the lithium iron phosphate battery in the air conditioning system. Compared with the BYDHan EV, Tesla Model 3 is more comprehensive, it is not only equipped with heat pump air conditioning, but also made additional efforts in the battery thermal management system, so it can also stand out among the ternary lithium battery models.
In fact, Xiaolei is not surprised that BYD and Tesla can make up for the shortcomings of lithium iron phosphate battery models under low temperature conditions. What Xiao Lei did not expect was that they were able to make their original deficiencies into their own strengths and complete a counterattack like a tortoise and a rabbit race.
Of course, from the current point of view, whether it is safety for ternary lithium batteries, or winter endurance for lithium iron phosphate batteries, power battery manufacturers have not chemically eradicated their problems. The reason why BYDHan EV and Tesla Model 3 equipped with lithium iron phosphate batteries can win in the low-temperature endurance test of China Automobile Research Institute is only by relying on the "side door left road", which can be used in lithium iron phosphate battery models, and can also be used in ternary lithium battery models.
In Xiao Lei's view, today's lithium iron phosphate battery models are just taking advantage of the ternary lithium battery models to take a nap. When the ternary lithium battery reacts, the advantage of lithium iron phosphate battery models in winter endurance will be surpassed.
It can be seen that the tortoise and rabbit race between lithium iron phosphate batteries and ternary lithium batteries is far from reaching the end. In the future, whether lithium iron phosphate batteries dominate the new energy vehicle market, or ternary lithium batteries dominate the new energy vehicle market, it also depends on how power battery manufacturers and new energy vehicle companies show their magic.
Note: The material for this article comes from the Internet