Why the charging speed will be slower after 80%?

We know that the charging speed for 0-80% charging will be fast. However, have you noticed that the charging speed for 80% to 100% will get slower? What about following us to reveal the secret of it?

The Regulation of the Battery Management System

As we may know over-current will harm the battery. To extend the service life of the vehicle power battery and ensure the safety and stability of the charging process, the battery management system matters. When the battery charge reaches around 80%, the battery management system will adjust and decline the charging current. The purpose of this is to avoid potential damage to the battery caused by overcharging, thereby effectively extending the battery’s cycle life.

The Regulation of the Battery Management System

The Effectiveness of the Resistance

There are three terms in the charging process, voltage, current, and resistance. As charging proceeds, the charging process inside the battery causes a gradual increase in resistance. It’s like increased wind resistance towards us, which restricts the smooth flow of electricity. When the charging reaches around 80%, the effectiveness of resistance becomes more and more significant, causing the charging current to decrease, which in turn causes the charging speed to drop significantly.

The Effectiveness of the Resistance

Temperature Changes During Charging

Temperature is one of the important factors that affect the performance of automotive power batteries. When the resistance becomes higher, the current will be more difficult to pass through the circuit, so more power is needed to push it, and the temperature will rise rapidly in the process. During the charging process, if the battery temperature is too high, it may cause safety problems such as thermal runaway; when the temperature is too low, the chemical reaction rate inside the battery will be greatly slowed down. Whether it is a high or low-temperature environment, when charging to 80%, the negative impact of temperature on the charging speed will be more prominent, resulting in the charging speed not being as fast as before.

the charging station to charge our electric cars

Characteristics of Electric Vehicle Batteries

The battery of a tram has unique chemical properties. When it is close to being fully charged, the reaction speed of the chemical substances in the battery will naturally slow down. To give another example, when people are hungry, they eat very quickly because they want to fill their stomachs as quickly as possible; but when people are not so hungry, they tend to enjoy their food slowly. This is because the chemical balance inside the battery gradually approaches saturation, so that in the later stage of charging, even if the input current is the same, the efficiency of actual conversion into battery energy will decrease, so the charging speed will also decrease.

After showing all these four factors, we can imagine the operation models we have now may come from them, such as the charging stations that charge based on charging time…

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