Electric car life is a mystery, is it the reason for the battery?

Date:Mar 11, 2019

Recently, the founder of the car and home, Li Xiang, bombarded the voyage of electric vehicles. "A lot of car brands are still promoting their own cruising range at the same speed when promoting electric vehicles, and even directly put such false mileage miles. On the car's buttocks." A number of media joint initiatives subsequently stopped using the constant-speed cruising range provided by the manufacturer in subsequent reports. A vigorous electric car cruising range was launched.

The cruising range of electric vehicles is undoubtedly the most concerned issue for consumers. However, the actual cruising range is inconsistent with the constant speed of the manufacturer's propaganda and NEDC's comprehensive working conditions, and it has become a major problem for consumers. When an electric car owner talked about the cruising range, he said that he was quite helpless. "My car manufacturer claims to have a constant speed of 360km and a total life of 305km. Actually, it will be air-conditioned in winter, and the battery life is only about 100 kilometers." Consumers can't help but ask. How far can my car run?

Consumers’ anxiety about mileage has always been accompanied by the development of pure electric vehicles, and the power battery has once again been pushed to the forefront. However, this "pot" of electric vehicle cruising range is difficult to back up with the battery alone.

Pay attention to the life of electric vehicles, the battery is not the "culprit"

There are many factors affecting the endurance of electric vehicles. They are roughly divided into two categories. The first category is the same factors as fuel vehicles, such as vehicle weight, wind resistance, tire diameter, etc. The second category is the unique factors affecting electric vehicles, such as batteries. , motor, electronic control, external environmental factors, etc. As far as the battery itself is concerned, there are three main factors affecting battery life: battery capacity, battery material, and battery system energy density.

Generally speaking, the larger the battery capacity, the more kinetic energy can be provided, and the longer the cruising range will be. This is like the size of the fuel tank will affect the battery life to a certain extent. However, it is worth noting that the larger the capacity of the battery pack, the better, because in the case of the same capacity of a single battery, the larger the capacity of the battery pack, the more the number of batteries required, which means the whole vehicle. The heavier the quality, the overweight body will have a negative impact on battery life.

For this reason, lightweighting has always been one of the important goals pursued by electric vehicles. In addition to the weight reduction of the body and other components, the battery pack also requires a lighter weight. Therefore, the selection of ternary materials with higher energy density has gradually become the mainstream.

At present, the commonly used batteries for passenger cars are lithium iron phosphate batteries and ternary lithium batteries, and each of the two batteries has advantages and disadvantages. In actual use, the lithium iron phosphate battery is resistant to high temperature, has good safety and stability, is inexpensive, and has good cycle performance. The energy density of the ternary lithium battery is high. In the case of the same battery capacity/weight, the erecting quality of the ternary lithium battery is lighter and the cruising range is longer.

However, the use of a ternary lithium battery with a high single-energy density does not mean that a higher cruising range can be obtained, which also relates to the system energy density of the battery pack. Only the reasonable layout of the battery pack structure, so that each cell can play its proper energy, the cruising range is more secure.

In addition to the battery, these factors will directly affect the battery life

A pure electric vehicle runs on the road, and it needs a three-electric system composed of a motor, a battery and an electric control to work together.

The motor is like the "heart" of an electric car. It is equivalent to the engine of a fuel car. As a driving unit, the performance of the whole vehicle has a strong correlation with the motor. The parameters such as the acceleration time and the maximum speed depend on the motor.

As the main console of the whole vehicle, the electronic control system determines the speed regulation and torque control of the motor. It also controls the battery discharge rate and the efficiency of the high-low voltage conversion of the whole vehicle. It must control the energy consumption and balance the performance. And to protect the safety of the battery and the motor while meeting the high dynamic vehicle response frequency.

It can be seen that the battery, the motor and the electronic control complement each other, and close cooperation is indispensable. Whether the motor and the electronic control have the best performance will directly affect the cruising range of the pure electric vehicle. Therefore, the battery life problem of electric vehicles cannot be simply attributed to the power battery. It should also pay attention to the important role played by electronic control and motor.

In addition, some external factors such as wind resistance, vehicle weight, speed, driving conditions, weather conditions, driving style, etc., will also affect the life of electric vehicles. Therefore, the cruising range is affected by many factors, and comprehensive evaluation is needed.

Reduce mileage anxiety, new technologies continue to promote industrial development

In recent years, power battery technology has developed rapidly. The energy density of passenger car battery systems averaged 97 watt-hours/kg in 2015 and rose to 111 watt-hours/kg in 2017. According to the battery China network statistics, the first batch of announcements in 2018 catalogues of pure electric passenger car systems with an energy density of 140 watt-hours/kg or less accounted for 59%, and the proportion in the last batch of announcements at the end of the year has dropped to 20%. The increase in system energy density has also indirectly promoted the year-on-year growth of new energy vehicle sales, which has a very positive impact on the development of the electric vehicle industry.

In addition to the increase in energy density, the development of diversified battery products such as hydrogen fuel cells and solid-state batteries has also injected new vitality into the electric vehicle industry. The application of diverse battery products and the innovation of battery technology are constantly promoting the development of the electric vehicle industry. It is believed that in the near future, the problem of the mileage of electric vehicles will gradually decrease. Just like today, we will not care too much about the cruising range of fuel vehicles.

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