What are real SOC, displayed SOC, maximum SOC, and minimum SOC?

The working conditions of batteries are very complex during actual use. Current sampling accuracy, charge and discharge current, temperature, actual battery capacity, battery consistency, etc. will all affect the SOC estimation results. In order to ensure that SOC more accurately represents the remaining battery power percentage and ensure that the SOC displayed on the meter does not jump, the concepts and algorithms of real SOC, displayed SOC, maximum SOC, and minimum SOC are designed.

SOC concept analysis

1.True SOC: The true state of charge of the battery.

2.Display SOC: SOC value displayed on the meter

3.Maximum SOC: The SOC corresponding to the single cell with the most power in the battery system. Minimum SOC: The SOC corresponding to the single cell with the least power in the battery system.

SOC changes during charging
1.Initial state
The real SOC, displayed SOC, maximum SOC, and minimum SOC are all consistent.

2. During battery charging

The maximum SOC and minimum SOC are calculated according to the ampere-hour integration method and the open circuit voltage method. The real SOC is consistent with the maximum SOC. The displayed SOC changes with the real SOC. The changing speed of the displayed SOC is controlled to be within an appropriate range to avoid the displayed SOC jumping or changing too much. quick.

3. During battery discharge

The maximum SOC and minimum SOC are calculated according to the ampere-hour integration method and the open circuit voltage method. The real SOC is consistent with the minimum SOC. The displayed SOC changes with the real SOC. The changing speed of the displayed SOC is controlled to be within an appropriate range to avoid the displayed SOC jumping or changing excessively. quick.

The display SOC always follows the real SOC change and controls the change speed. The real SOC is consistent with the maximum SOC when charging and the minimum SOC when discharging. The real SOC, maximum SOC, and minimum SOC are all BMS internal operation parameters that can jump or change rapidly. The displayed SOC is the instrument display data, which changes smoothly and cannot jump.

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