Battery SOC Meaning
Description
Battery SOC refers to the State of Charge (State of Charge), which reflects the percentage of the remaining power of the battery at a certain time in the total capacity, and is an important parameter in the battery management system (BMS),here is a detailed description about it:
1.Meaning and function
1.1 Assess the remaining battery level
The SOC can intuitively tell the user how much power is left in the battery, just like the fuel gauge of the car, so that the user has a general understanding of the time or mileage that the device or vehicle can continue to run, so that the corresponding arrangements can be made in advance, such as charging plans.
1.2 Optimize battery usage
For the management system, accurate monitoring and control of SOC helps to optimize the charging and discharging process of the battery, avoid overcharging or overdischarge to cause damage to the battery, thus extending the service life of the battery,for example, when the SOC approaches 100%, the battery management system will appropriately reduce the charging current to prevent the battery from overcharging; when the SOC is low, it will remind the user to charge in time to avoid excessive battery discharge.
2.Influencing factor
2.1 Battery charging and discharging history
The number of charge and discharge times, the depth of charge and discharge and the rate of charge and discharge will affect the calculation and accuracy of SOC. For example, frequent deep charge and discharge may cause the battery capacity to decay, which can skew the SOC’s calculation.
2.2 Battery temperature
Temperature has a significant effect on the performance of the battery, and the charging and discharging efficiency of the battery is different at different temperatures, which affects the measurement of SOC. In general, at low temperatures, the available capacity will be reduced, and the SOC may decline faster than at room temperature; at high temperatures, the battery may have an increased risk of overcharge or overdischarge, which will also affect the accuracy of the SOC.
2.3 Self-discharge
Even if the battery is not charged and discharged, there will be a certain degree of self-discharge, which will cause the battery power to gradually decrease, thereby reducing the SOC. The rate of self-discharge is related to the type, quality and storage conditions of the battery.
3.Measurement method
3.1 Ampere-hour integration
The charging state of the battery is calculated by integrating the charging and discharging current of the battery,this method is simple and direct, but it is affected by factors such as current measurement errors, battery self-discharge, and capacity changes, and requires regular calibration.
3.2 Open-circuit voltage method
The SOC is estimated based on the relationship between the open circuit voltage and the SOC. Generally speaking, the open circuit voltage will change with the change of SOC, but this relationship is not linear, and is affected by battery temperature, aging degree and other factors, so the accuracy of measuring SOC using the open circuit voltage method alone is limited.
3.3 Impedance spectroscopy
The SOC is calculated by measuring the AC impedance to obtain the information inside the battery,this method can measure SOC more accurately, but requires specialized equipment and the measurement process is more complex, and is generally used in laboratories or high-end battery management systems.