The charging control method mainly refers to a method for judging the end of the battery charging process. It mainly includes capacity control method, timing control method, maximum voltage control method, voltage change rate control method, minimum current control method, maximum temperature control method and temperature change rate control method. By combining the charging control method with the basic charging method, the battery charging measures can be more perfect.
1. Capacity control method
The method judges whether to end the charging process by calculating in real time the change of the battery power during the charging process, and ends the charging when the battery power reaches the set value. Since the initial power value of the battery varies before each charge, it is necessary to manually set the charged power. This charging control strategy can be applied to the on-board charger, and the power battery management system (BMS) provides data such as initial power. However, the reliability of this control method is currently restricted by some factors, such as the accuracy of the remaining power (SOC) information of the battery pack and the battery capacity that decreases with time.
2. Timing control method
Restricted by the set charging time, using a timer for timing charging can easily meet the control requirements, and has the advantages of simple method and strong operability. However, this control strategy cannot be automatically adjusted according to the state of charge of the battery, and it is prone to undercharge or overcharge, which is not conducive to the maintenance and maintenance of the battery.
3. Maximum voltage control method
This method is mainly used for constant current charging. During the charging process of the battery, when the battery voltage reaches a certain fixed value, the battery is considered to be fully charged, and the charging process ends at this time. In order to prolong the service life of the battery, the corresponding voltage values are different when the battery is fully charged. If only a single maximum voltage value is set to determine whether the charging is completed or not, there may be a large error. In addition, the maximum voltage setting value of different models of batteries produced by different manufacturers is also different.
4. Voltage change rate control method
According to the charging characteristic curve of different batteries, the method judges whether to end the charging process through the voltage change rate. The terminal voltage of the battery changes continuously as the charging process continues, and the phenomena such as the voltage increase, the voltage reaching the maximum, the voltage tending to be flat, and the voltage negative increasing appear in sequence. When the change of the battery voltage is consistent with the preset change rate, it can be regarded as the termination of the charging process. This charging strategy is less affected by the difference in battery types, and the judgment result obtained based on the voltage change rate curve is relatively accurate.
5. Minimum current control method
This method is usually used in conjunction with the constant voltage charging method, when the battery is charged at a constant voltage, as the battery voltage increases, the charging current gradually decreases, and when it decreases to a certain value, it is considered that the battery has been fully charged, and the charging process is completed.
6. Maximum temperature control method and temperature change rate control method
The maximum temperature control method and the temperature change rate control method are also two commonly used control strategies for terminating the charging process. Temperature reflects the degree of electrochemical reaction inside the battery and is an important parameter in the charging process. It is relatively simple to measure the temperature of the battery, but due to the influence of factors such as charging method, ambient temperature, temperature hysteresis, and sensor accuracy, errors are prone to occur during measurement. Therefore, under normal circumstances, these two charging control strategies need to cooperate with the implementation of other control strategies as an auxiliary judgment basis for stopping the battery charging process.