It's 2024. Can't electric vehicles withstand temperatures as low as minus 20 degrees?

In winter, the endurance of new energy vehicles in China undergoes a concentrated test.

In the winter of 2024, the new energy vehicle market will usher in the largest collective inspection in history. According to data released by the Ministry of Public Security, as of the end of June this year, the number of new energy vehicles in the country has reached 24.72 million. In the first half of this year, 4.397 million new energy vehicles were newly registered, with a year-on-year growth of 39.41%, setting a new historical high. The market penetration rate of new energy vehicles has exceeded 50% for several consecutive months.

With the continuous development of technologies such as batteries and high-voltage platforms for pure electric vehicle models, the market acceptance of pure electric vehicles is also constantly increasing.

However, the regional distribution is uneven. Currently, the top ten cities with the highest sales of pure electric vehicles are mostly concentrated in the southeastern and southwestern regions, with only two northern cities - Tianjin and Xi'an. This is related to the lower winter temperatures in the north, where the endurance of pure electric vehicles will significantly shrink under low-temperature conditions.

Perhaps in many people's impression, the "culprit" that affects the endurance of electric vehicles in low winter temperatures is the battery, because the activity of the battery itself decreases in a low-temperature environment. But in addition, there are many other influencing factors, such as battery capacity, charging and discharging capacity, electric drive efficiency, cabin heating, wind resistance, and rolling resistance.

If you don't want car owners to start the annual "imprisonment" experience as soon as the season arrives, you need to ensure that all the components in the vehicle can work in a comfortable environment. This requires efforts in many aspects, such as providing batteries with longer endurance and better low-temperature retention, a more efficient thermal management system, and a battery management system.

However, technical theories are just theories, and the specific results still depend on the actual test results.

This winter, we once again came to Inner Mongolia and brought the Tesla Model 3 and the Zhijie New S7, which claims to be relatively leading in the same class with a summer endurance of up to 855 km. Through a hardcore actual test, let's see if in 2024, electric vehicles can still withstand a temperature of minus 20 degrees Celsius?

Low Temperature Remains a Great Test for Electric Vehicles

The working principle of electric vehicles determines that they will encounter problems such as power attenuation, preheating energy consumption, increased mechanical friction, and energy-consuming air conditioning heating in a low-temperature environment.

The cold not only significantly reduces the endurance but also leads to a series of chain reactions such as slower charging speed and longer vehicle preheating time. Just looking at the endurance achievement rate, from the ranking of pure electric vehicle models in the "Dongchedi" winter test at the end of 2023, the best result is also less than 60%, which is almost halved.

This time, the models we tested are the Zhijie New S7 Ultra Four-wheel Drive Long-Endurance Version and the Tesla Model 3 Long-Endurance All-Wheel Drive Version. The official endurance of these two vehicles is 785 km and 713 km respectively, the battery pack sizes are 100 kWh and 78.4 kWh respectively, and both use ternary lithium batteries.

In the Inner Mongolia region, where the average daily temperature is in the range of minus 15 to minus 20 degrees Celsius, we tested the low-temperature pure electric endurance fulfillment rate, low-temperature cold vehicle charging efficiency, and low-temperature cold vehicle air conditioning system heating efficiency of these two vehicles.

The test results show that the endurance of both pure electric vehicle models has been discounted. From a fully charged state to a zero power state, the actual driving mileage of the Zhijie New S7 is 467.2 km, and the Tesla Model 3 actually traveled 371 km, with endurance fulfillment rates of 59.7% and 52% respectively.

The two vehicles tested are the flagship models of their respective brands, indicating that extremely cold low temperatures remain a great test for electric vehicles. However, the long endurance of the vehicle itself can provide more endurance redundancy space for the vehicle in low-temperature conditions, allowing the Zhijie New S7 to travel nearly 100 kilometers more than the Tesla Model 3.

To improve the endurance mileage of pure electric vehicle models in a low-temperature winter environment, there are essentially two paths - increasing the source and reducing the consumption.

Increasing the source means using larger batteries and better battery materials to achieve longer endurance. This is because the battery is the main driving source of an electric vehicle. When the temperature drops, the electrolyte inside the battery becomes viscous, and the lithium-ion migration rate slows down, resulting in a decrease in battery activity. At the same time, a temperature drop also leads to a decrease in the charging and discharging power of the battery and the available energy of the battery.

Ternary lithium batteries have better low-temperature stability and higher energy density than lithium iron phosphate batteries, but they are also more expensive. Currently, the average quoted price of lithium iron phosphate battery systems is below 1 yuan/Wh, and the cell price is around 0.6 - 0.7 yuan/Wh. The average quoted price of ternary battery systems is around 1.1 - 1.3 yuan/Wh, and the cell price is around 0.9 - 1.05 yuan/Wh. This means that the cost of ternary lithium batteries is at least 10% - 30% higher than that of lithium iron phosphate batteries.

A larger battery pack also means a higher price. But for various car companies in the current fierce price war, this is only one of the options that some companies are willing to invest heavily in. To improve the winter endurance efficiency of electric vehicles, providing a large battery is only one of many optimization approaches. 

Tailored Solutions, Two-pronged Approach

In addition to increasing the source, reducing consumption is also necessary - that is, minimizing the energy consumption in each link as much as possible, and this requires "meticulous efforts".

Before understanding how to improve the winter endurance of electric vehicles, we need to first know what factors will affect the low-temperature endurance of electric vehicles. Only in this way can we "tailor the solution to the problem".

In addition to the battery, there are many other factors that affect the winter endurance mileage of new energy vehicles. Increased energy consumption from driving and heating in the cabin are the main factors.

Studies have shown that the energy consumption from driving is one of the main factors that lead to increased energy consumption of vehicles in low-temperature conditions, accounting for 75% of the vehicle's total energy consumption.

In low-temperature conditions, the driving energy consumption of electric vehicles also increases. This is because the physical properties of the materials change in low-temperature conditions. For example, the tires and the lubricating oil used in the drive system. At minus 7 degrees Celsius, the tires will become harder in winter, and the rolling resistance will increase by 50% compared to normal temperature; in low temperatures, the lubricating oil in the drive system will also become viscous, and the efficiency will decrease by 2%. To make the lubricating oil work properly, some thermal energy also needs to be consumed, etc.

In low-temperature weather, the external conditions also change. A vehicle electric product manager of a new energy vehicle company once told us that the wind resistance process can be understood as the vehicle hitting the molecules in the air during driving. "In low-temperature weather, the molecular density in the air becomes higher, and the number of molecules hit by the same vehicle will also increase, which will increase the energy consumption of the vehicle during driving."

The remaining 25% of the energy consumption is the energy consumption of the air conditioning. Heating the cabin in a winter electric vehicle is more challenging than cooling in summer because the difference between the actual external temperature and the cabin temperature in winter is greater, with a maximum temperature difference of up to 60 degrees.

These will all lead to a significant discount in the endurance mileage of pure electric vehicles in winter.

To reduce the energy consumption from driving and air conditioning heating, these are strongly related to the vehicle's own drive system and thermal management system.

The traditional thermal management system is itself relatively complex, with many pipelines, components, and energy transfer levels, which leads to a relatively fast energy consumption; at the same time, it has poor adaptability to low-temperature environments. Below minus 10 degrees Celsius, it is very difficult to start the vehicle; in addition, the efficiency and intelligence level are low, and there is no way to implement a precise energy recovery strategy for the vehicle.

Improving the efficiency of the vehicle's own thermal management system is a key direction in the industry for optimizing the energy consumption of electric vehicles. For example, the Zhijie New S7 uses the Huawei TMS thermal management system. This thermal management system has a higher integration level, and the components are redesigned. While reducing the number of components, the pipeline length is also reduced, which also reduces some pipeline heat loss.

In addition to a higher integration level, another direction for optimizing the thermal management system at the current stage is intelligence. In the original thermal management system, various calibrations need to be done manually, but now it is more intelligent control.

For example, the thermal management system on the Zhijie New S7 can intelligently control the heating of each seat, the steering wheel, and the air conditioning temperature, and rationally allocate to significantly reduce energy consumption. In practical applications, the heat in the vehicle can also be flexibly distributed to ensure comfort while saving electricity. According to Zhijie officials, compared to the traditional electric heating system, the energy consumption of the Zhijie New S7 can be reduced by 50%.

To optimize the driving energy consumption, using a more efficient motor platform and a lighter body design is also one of the solutions. For example, the Zhijie New S7 is equipped with the HUAWEI 800V High-Voltage Silicon Carbide High-Efficiency Power Platform, which adopts a flat wire winding and a high-voltage silicon carbide module, has a maximum speed of 22,000 rpm, a maximum efficiency of 98%, and the silicon carbide has a 4.4% higher efficiency than the IGBT assembly, with very low energy loss of the motor.

In addition, the drag coefficient of the Zhijie New S7 is only 0.203Cd, and the low-rolling-resistance tires reduce the impact of the hardness of the winter tires. Energy braking recovery and other strategies also contribute to the ultra-low energy consumption of the Zhijie New S7.

For cooling, the principle of new energy vehicles is similar to that of traditional vehicles. For heating, the air conditioning system of traditional vehicles uses the waste heat of the engine for heating; while electric vehicles use PTC (Positive Temperature Coefficient Thermistor) for heating. However, PTC has a lower heating efficiency because it uses heat conversion.

In the industry, the heat pump solution is commonly used for the battery performance of pure electric vehicles in low-temperature conditions, including the Tesla Model 3 and the Zhijie New S7 tested this time. Because in the same environment, the heating efficiency of the heat pump heating is 1.8 - 2.4 times that of PTC, and at the same time, the endurance mileage loss caused by heating can be restored to 40% - 50%.

But even for models with the same heat pump air conditioning, the performance is very different. For example, in this test, the air conditioning heat pump of the Tesla Model 3 will make a loud and sharp noise in various working conditions such as charging, driving, and parking, affecting the driving and riding experience.

This is strongly related to whether the product attaches importance to the user experience from the project's initiation.

Today's vehicles not only emphasize the vehicle's own tool attributes but also emphasize the user's experience, emphasizing that the vehicle is a mobile and warm space. When the extremely cold winter comes, the endurance extension solution designed by car companies not only needs to consider endurance, efficiency, and cost but also, most importantly, the user's experience.

The continuously evolving new energy vehicle industry is not lacking in 800V pure electric high-voltage platforms, nor is it lacking in ultra-large batteries with an endurance of up to 800 km, nor is it lacking in heat pump air conditioning. What it lacks is a good product with no obvious shortcomings, starting from the user, and with the best comprehensive experience. Using technology to solve the endurance anxiety in low-temperature winter travel is the original intention, but on the way to achieving longer endurance, the product concept of user-oriented should also be continuously implemented.

This article is from the WeChat public account "36Kr", and 36Kr is authorized to publish it.