Since the editor bought a tram, he has had to charge his car every few days. However, slow charging takes 7 or 8 hours to fully charge, while fast charging takes less than an hour to reach 80% of the battery. It is also more convenient for outings or emergencies, and I have gradually become accustomed to using fast charging to charge the electric car. By chance, I learned that fast charging would increase the safety risks of trams, so I also reduced the number of fast charging times.

　　So for electric vehicles, what impact will fast charging have on electric vehicles? How much harm will it cause? Let’s talk about this topic together today.

　　Fast charging causes the critical point of battery thermal runaway to decrease

　　Many experts have said that the main reason for electric vehicle fires is due to high-power fast charging. According to statistics, among new energy vehicle accidents in 2018, the accident rate directly or indirectly caused by the use of fast charging was as high as 29%. Mainly because the stability of the battery will deteriorate after fast charging 300-500 times. The thermal runaway temperature of ordinary ternary lithium batteries is about 215 degrees, while the thermal runaway critical of ternary lithium batteries that are frequently fast-charged will drop to 107 degrees. , it is more likely to trigger a fire event caused by thermal runaway of the battery.

　　If calculated based on the use of fast charging 2-3 times per week, it is about 120 times per year. In less than three years, electric vehicles will face the risk of the critical point of battery thermal runaway decreasing, which is a problem worthy of vigilance for current electric vehicle users.

　　With the current technology, it is difficult to solve the problem of the thermal runaway critical point of the battery caused by fast charging. Technical means can only delay the decline time.

　　Frequent fast charging causes battery capacity to decay

　　The essence of fast charging is to store DC power directly inside the battery, but the DC power is very large. The voltage during charging is around 400V-500V, and the current is around 20A-30A. During the charging process, a large number of electrons continue to accelerate from the positive electrode to the negative electrode of the battery. This process will generate high heat, and due to the increase in temperature, the semipermeable membrane (similar to the separation wall) on the surface of the negative electrode of the battery will be exists to separate the electrode material and the electrolyte to prevent them from reacting) and rupture. At the same time, it will also react to produce foreign matter on the electrode and decompose the electrolyte. Over time, the battery capacity will slowly decrease.

　　Faced with battery capacity fading: what should users do?

　　The attenuation of battery capacity due to fast charging is unavoidable, so when buying a car, everyone should pay more attention to the battery warranty service provided by the manufacturer. At present, many manufacturers have also proposed solutions to this problem. NIO ES8 provides a lifetime battery warranty service. When the battery power loss reaches 15%, it will enjoy the warranty and provide battery replacement service. Xpeng G3 provides an 8-year or 150,000-kilometer warranty system. During this period, if the fast charging loss reaches 10% after 500 times or 20% after 1,000 fast charging times, you can enjoy free battery replacement and other services. WM EX5 provides an 8-year or 150,000-kilometer warranty system. During this period, if the power loss reaches 20%, you can enjoy free battery replacement and other services.

　　Summarize

　　The biggest problem caused by fast charging is the decrease in the critical point of battery thermal runaway and the attenuation of battery capacity. Even though some manufacturers have begun to provide battery replacement services for batteries with large losses, they are still unable to technically solve the danger caused by the decrease in the critical point of battery thermal runaway. Therefore, car owners should try to use slow charging and timely charging during daily use of pure electric vehicles, and use fast charging in emergency situations to prevent battery capacity decay and improve battery stability.

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