The main body of charging is slow charging and fast charging is only for emergency use

Aiming at the question of fast charging or slow charging of electric vehicles, Ouyang Minggao, academician of the Chinese Academy of Sciences, professor of Tsinghua University, and director of the State Key Laboratory of Automobile Safety and Energy Conservation, pointed out at the Xumishan Conference held in Changzhou, Jiangsu Province on March 30 that the future of electric vehicles The development direction of charging mode. He said, "In the future, in the charging of passenger cars, the main body will be slow charging, and only about 20% of the cases will need fast charging, and fast charging is only for emergency use."

Ouyang Minggao pointed out that slow charging has many benefits, especially when it is combined with smart grid in the future, slow charging is not only for charging, but also to balance the fluctuation of the grid, play the role of energy storage, and at the same time, it can also send electricity back to the grid. He believes that fast charging is only a means of emergency assistance, and the development of fast charging should consider the input cost. If the cost is very high, you can consider replacing the battery.Also read:500ah lithium battery

He believes that fast charging is only a means of emergency assistance, such as on the highway. In fact, there are obvious defects in maintaining high-current fast charging all the time. Just like pouring beer too quickly will produce foam, but it will not be full, the electrochemical reaction inside the battery takes a certain time, and charging with an excessive current will cause the battery to not be fully charged.

Ouyang Minggao said that in order to make the charging speed of electric vehicles faster, fast charging with a maximum output power of 350kW can be achieved from the perspective of chargers, but it has a greater fundamental impact on power batteries and complete vehicles. If you want fast charging, it doesn’t matter how much power the charger can accept, the core issue is the charging rate of the battery, which determines whether fast charging can be realized. The charge-discharge rate refers to the speed at which energy is stored and released. The higher the current, the higher the charging rate and the faster the charging. As a power battery, in addition to satisfying fast charging, it also needs to meet people's basic requirements for the cruising range of the car, and the cruising range is determined by the energy density (Wh/kg) of the battery. Without considering the energy density, making the pole piece of the battery very thin can achieve a large charge rate; on the other hand, with the continuous improvement of the energy density of the battery, the pole piece of the battery needs to be made Thicker to reduce energy loss due to polarization. Therefore, batteries with a charging rate of 30C can be achieved at present, but it is very difficult for batteries with high energy density to achieve a charging rate of up to 3C, and it is far from the requirements of fast charging.

"Overall, we need more technological innovations for emergency fast charging." Ouyang Minggao said that at present, an electric car needs about 60 kilowatt-hours of electricity, and it only takes half an hour to use such a charging pile. full. In the case of emergency fast charging, it is equivalent to charging an electric vehicle for 10 kilometers for 1 minute and 150 kilometers for 15 minutes, which can fully meet the immediate needs. When the remaining power reaches more than 70%, the charging power drops sharply. Therefore, Ouyang Minggao believes that fast charging is definitely not to fully charge the battery.

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