Method and system for estimating remaining available capacity of lithium ion power battery pack

Abstract

The invention discloses a method and system for estimating remaining available capacity of a lithium ion power battery pack. The method comprises the following steps: recording the current value in the charging process and the time used by charging, and calculating the total available capacity of the lithium ion battery at the starting time of discharging, thereby obtaining the total available capacity A of the lithium ion battery; recording the open-circuit voltage and the voltage drop delta V in the discharging process, selecting the curvilinear function used by calculating the remaining available capacity percentage through the voltage drop delta V, and obtaining the remaining available capacity percentage a of the lithium ion battery; obtaining the service efficiency of the remaining available capacity SOC of the battery at the current temperature by utilizing the relation between temperature and remaining available SOC; and adding A*a* of all the batteries to obtain the remaining available capacity of the lithium ion battery pack. The system for realizing the method comprises a voltage, current and temperature monitoring module for monitoring the battery pack information, the monitoring module feeds the monitored information back to the MCU, and the MCU outputs the estimated remaining available capacity of the lithium ion power battery.

Description

technical field The invention belongs to the technical field of battery management, in particular to a method and system for estimating the remaining available capacity of a lithium-ion power battery pack. Background technique At present, the methods for estimating the remaining available capacity of lithium-ion power battery packs are: (1) Measure the effective mass of the battery electrolyte The SOC (residual capacity) value is calculated by measuring the effective mass of the battery electrolyte. This method is more suitable for lead-acid batteries that can directly measure the quality of electrolyte, and theoretically can accurately measure SOC. However, at present, pure electric and hybrid applications mainly use nickel-metal hydride batteries and lithium batteries, both of which are closed structures. There is no effective means to accurately measure the effective mass of the battery electrolyte online, and there is no practical application value. (2) Calculation...

AI Technical Summary

Problems solved by technology

This method has the following problems: ① The AC impedance of the battery pack only has a relatively large change rate when the battery SOC is very low or high, and the change rate is very small when the SOC is in the middle. If the measurement is not accurate enough, the calculation The error will be relatively large; ②The AC impedance of the battery is affected by many nonlinear factors, such as temperature, the state of charge and discharge at the previous moment, whether it is fully static, etc., there may be different AC impedance values ​​under the same SOC, or the same There may be different SOC values ​​under the AC impedance value, and a definite one-to-one correspondence cannot be found; ③The AC impedance value of the battery pack is not only determined by the chemical characteristics of the battery, but also batteries with different plate structures and electrolyte formulations will show different At the same time, the manufacturing process of the battery also plays a very important role, even if there are differences in the correspondence between the AC impedance and the SOC between different batches of batteries of the same production process; ④ Calculated at different current frequencies There may be a relatively large difference in the AC impedance that comes out

This method makes up for the defect that the "open circuit voltage method" cannot be measured online in real time, but has the following shortcomings, which cannot achieve the purpose of accurately calculating SOC: ① It is necessary to accurately measure the OCV-SOC curve; ② It is required to accurately establish a battery model; ③ It is required to accurately calculate the impedance parameters in the battery model. Usually, these parameters are affected by nonlinear factors such as temperature, current, charge and discharge state, etc., so it is difficult to calculate accurately, and small changes in these parameters will cause a large impact on the calculation of OCV. error, thus affecting the estimation accuracy of SOC

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