A method for correcting lithium battery SOC according to dynamic voltage

Abstract

The present invention proposes a method for correcting the SOC of a lithium battery according to the dynamic voltage, which includes the following steps: S1: obtaining the relationship between the dynamic terminal voltage and the SOC of the battery at different temperatures and different rates through experiments; S2: selecting the charging process and the discharging process according to the characteristics of the battery Calibration point during the process; S3: In the process of driving discharge, it is judged in real time that the current is less than the set threshold, and the voltage is less than the threshold corresponding to the current temperature. The SOC corresponding to the calibration point is calibrated; S4: During the charging process, it is judged in real time that the current is less than the set threshold value and the voltage is less than the threshold value corresponding to the current temperature, if the current SOC is less than the SOC corresponding to the calibration point, then the current SOC is transferred to the SOC corresponding to the calibration point calibration. The algorithm operation is performed in real time during the driving process, so that the program does not depend on the special working conditions of standing, and the smooth change of the SOC will not be abruptly changed during the SOC calibration process.

Description

technical field [0001] The invention relates to the field of battery management systems, in particular to a method for correcting the SOC of a lithium battery by using the terminal voltage of the battery during discharge to reduce the SOC error. Background technique [0002] As one of the core components of electric vehicles, the battery management system (Battery Management System, BMS) has always been the focus of electric vehicle research and development. Due to the complex working environment and working conditions of electric vehicles and the complex chemical characteristics of batteries, compared with traditional fuel vehicles, the main technical difficulty of new energy vehicles lies in the accuracy of mileage estimation. SOC is the most important parameter for calculating cruising range, and SOC calculation has become one of the core functions of BMS. The accuracy of SOC calculation directly determines the quality of BMS. [0003] At present, the ampere-hour integra...

AI Technical Summary

Problems solved by technology

However, there are obvious defects in the ampere-hour integration method: 1. The accuracy of the ampere-hour integration algorithm depends on the accuracy of the current sensor, and in the case of a systematic error in the current sensor, the long-term pure ampere-hour integration strategy will inevitably lead to an increase in the error of the SOC. getting bigger

2. Due to the self-discharge phenomenon of lithium batteries, and the ampere-hour integration does not take this into account, the long-term pure ampere-hour integration algorithm will inevitably lead to a falsely high SOC

4. When fully charged, it is directly calibrated to 100% according to the current voltage condition, and the SOC may jump.

But this scheme also has obvious disadvantages: 1. In this method, there are clear requirements on the working conditions of the vehicle, and there must be enough standing time

2. In view of the plateau period of lithium iron phosphate batteries, the voltage change range is very small in the range of 30% to 90%. The voltage acquisition accuracy of the current BMS is generally 5mv, and the OCV calibration scheme will have a huge error

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