Briefly describe the method for estimating the remaining power of the lithium-ion battery, and what is the usable range of the battery SOC system

The SOC (stateofge) estimation algorithm of lithium-ion batteries is one of the key technologies for the development and application of battery management systems (BMS). The accuracy and stability of the battery SOC system is very important. It will directly affect the user's use of the product, and the user must make a judgment on when it needs to be charged based on the remaining power data provided by the battery's SOC system. Roughly speaking, the definition of SOC is that SOCu003dremaining capacity/rated capacity (full charge capacity)*100%. SOC usable range; SOC range minus SOC buffer area, the remaining part is SOC usable range. The percentage of SOC state range is generally from 0% to 100%, but considering the chemical battery reaction characteristics: threshold boundary, static and dynamic difference, magnification difference, estimation accuracy difference, etc., SOC estimation should be set aside in the buffer zone to ensure Lithium-ion batteries always work in a safe area. The optimization of the available range of SOC is to determine the lower limit of the battery under different conditions and working conditions. The upper limit of the lithium-ion battery cache interval is very small, and there is not much room for mining. The upper limit of the cache is important in terms of charging safety, to ensure that it is not charged for the purpose. The SOC is 80% in fast charging; it can reach more than 95% in slow charging by trickle current charging. The lower limit of the battery is important to consider the discharge conditions and the ability to change the discharge current, which will affect the power output or driving experience. At the same time, the width of its cache is still very large. Lithium-ion battery remaining power estimation method; open circuit voltage method: first off-line measurement to obtain the open circuit voltage value at different temperatures and different SOCs, and form a table. After the battery system is installed in the vehicle, whenever the power supply is stopped, the table data can be called to judge the battery state of charge based on the measured open circuit voltage. Ampere-hour integration method: real-time measurement of the current in the main circuit of the lithium-ion battery pack, and integrating it over time, charging is negative and discharging is positive. In the discharging process, the initial power is subtracted from the integration result to get the current power; in the charging process, the initial power is added to the integration result to get the current power. Internal resistance method: The tendency of internal resistance to follow the SOC change is very gentle, and a small internal resistance change or measurement error can cause a large error in the SOC value. The measurement contact resistance is too large, the battery current is large, and there is a large polarization internal resistance interference; the inconsistent temperature rise of the lithium ion battery makes the temperature of the temperature monitoring point and the battery body temperature inconsistent, resulting in deviations in temperature compensation, and so on. Kalman filter algorithm: The core idea is to calculate the current optimal value based on the current measurement value of the instrument, the forecast at the previous moment, and the error. The highlight is that the error is included in the calculation, and the error exists independently and is not affected by the measurement data. Neural network algorithm: A new algorithm that simulates the human brain and neurons to process nonlinear systems. There is no need to deeply study the internal structure of lithium-ion batteries. You only need to extract input and output samples that meet the working characteristics from the lithium-ion battery in advance. It is input into the establishment system to obtain the running SOC value. Disclaimer: Some pictures and content of the articles published on this site are from the Internet. If there is any infringement, please contact to delete. Previous article: What is a super capacitor? How are supercapacitors charged?