Why is the battery of a pure electric car always undercharged?

Legendary "safety redundancy"

The electric car is really undercharged. In fact, the battery capacity we usually refer to is the nominal power, which is the data obtained by multiplying the capacity of a single battery by the total voltage of the battery pack. But in fact, manufacturers make "minor errors" with the battery on the vehicle. For example, the original battery capacity is 100%, but it can be used about 80%-90%.

The reason why manufacturers do this is actually the result of considering the "safety" of the battery. Because during the charging process, the battery cannot be filled too full, and at the same time cannot put the power into space. If the battery is fully charged each time, it will greatly reduce its service life. In addition, if the charge is too full, once the charging system is faulty, there may be a safety accident due to "overcharge". In life, our most common example is to flood your phone with some brand-name chargers. In general, battery management systems generally reserve a certain amount of "bottom redundancy" as a guarantee. This is mainly because if the vehicle is stored for a long period of time, there must be a small amount of surplus power when the consumer thinks that the power reaches 0%.

Speaking of which, I have to say Tesla. When the charge reaches 100%, Tesla will retain 10% of the charging space and cannot charge. When the battery capacity is displayed at 0%, it also retains 10% of the charge unable to release. In fact, Tesla can only use 80% of the battery's true capacity. Similarly, domestic car companies are similar in the setting of power battery safety redundancy. Take BYD as an example. Although the battery uses lithium iron phosphate power battery, it also retains 2~3% redundancy at the upper end. It retains about 6 to 8% redundancy and retains less power than Tesla.

Therefore, it is because of the redundancy of the battery that the battery is completely removed by 10%~20%. In fact, the value after the power redundancy is the actual power that the owner can use, not the nominal power in the announcement.

What is the impact of battery power?

In addition to the above reasons for power redundancy, there are still many factors that affect the battery power.

1. When the vehicle is experiencing rapid acceleration and deceleration during driving, this requires the motor to turn faster, and also requires the battery to supply more power, but in fact, the larger the power consumption, the same capacity ratio The lower the voltage, the result is that a few percent of the power is not available.

2. Temperature is also a big killer of the battery. Many people have feelings. In the winter, driving a pure electric car is particularly fast. From the figure, we can clearly see that from normal temperature of 25 degrees to -20 degrees, the battery discharge is reduced by 30%.

Not only that, in low temperature charging, some manufacturers to ensure the safety of low temperature charging, but also reduce the charging current, thus increasing the charging time. From room temperature to -25c, the charging time is extended by more than 40%.

3. When driving in winter, air-conditioning heating also requires batteries to provide energy, which consumes one kilowatt hour in about half an hour.

4. The normal decay of battery power, generally after 2 or 3 years of driving, the battery of pure electric vehicles will show signs of attenuation.

3. When driving in winter, air-conditioning heating also requires batteries to provide energy, which consumes one kilowatt hour in about half an hour.

4. The normal decay of battery power, generally after 2 or 3 years of driving, the battery of pure electric vehicles will show signs of attenuation.

In addition, experts also said that when the vehicle is stored statically, the battery's power will gradually decay.

Summary: When we understand the difference between the nominal power and the actual charge, we can understand why the charging of pure electric vehicles does not match the power marked by the manufacturer. After all, all this is to ensure battery safety. Moreover, the life of the battery is closely related to driving habits and environmental temperature factors, which requires the driver to maintain a good driving habit, thereby extending the battery life.

The page contains the contents of the machine translation.