Correction method of SOC in the whole life cycle of lithium battery system

Abstract

The invention discloses a method for correcting the SOC of a lithium battery system in its entire life cycle. For the positive correction of the battery system, when the battery is discharged to a real SOC ≥ 4%, the undervoltage of the battery will be cut off, and the battery will be charged to the highest voltage cut-off point of the battery. When the temperature T≥5°C, calculate the capacity corresponding to the SOC of the battery system being 100%. Compared with the capacity value calculated last time, if it exceeds +5%, it will be corrected according to +5%, if it is lower than +5% and higher than +3%, it will be corrected according to the actual value, and the rest of the conditions will not be corrected. Reverse correction of the battery system, when the battery system is discharged to SOC ≤ 4%, if the minimum battery temperature is higher than 5°C and the discharge current is greater than or equal to 16A, and the minimum voltage of the monomer is higher than 2.8V, then upward correction is made by 1%, otherwise no Make an upward correction. The method of the invention has high practicability, and after the SOH value deviation is corrected by the invention, the accuracy of SOC calculation in the whole life cycle of the lithium iron phosphate battery system can be realized.

Description

technical field [0001] The invention relates to the field of electric vehicle battery pack systems, in particular to a method for correcting the SOC of a lithium battery system in its entire life cycle. Background technique [0002] In the prior art, the capacity calculation after battery cycle mostly adopts the following methods: 1. By testing the cycle life of the battery system, the number of cycle life of the battery is obtained, and then this value is inserted into the SOC calculation, combined with the battery temperature to determine Calculate the attenuation of the battery after actual use. 2. Calculated by the open-circuit voltage look-up table method, that is, the voltage of the single battery changes from V1 to V2 under the condition of charging and discharging the vehicle (V1, V2 are the open-circuit voltage of the battery after standing), and SOC1 and SOC2 can be obtained by checking the OCV table , the voltage change process can be integrated through the amper...

AI Technical Summary

Problems solved by technology

By testing the cycle life of the battery system, the number of cycle life of the battery is obtained to calculate the battery capacity after the cycle. Considering that the operating environment of the real vehicle is different from the laboratory environment, the cycle life of the battery system on the real vehicle is much lower than that of the experiment. Laboratory data, the error is very large, and the test cycle is too long. Generally, it can only be tested 3 times in 24 hours, and the test should be at least 200 times

2. Calculating the remaining capacity of the battery system after the cycle through the open circuit voltage look-up method is only suitable for batteries with a large curvature of the battery SOC-OCV curve, such as ternary batteries and lithium manganese oxide batteries

Since the slope of the SOC-OCV curve of lithium iron phosphate battery is small and relatively stable, the difference between open circuit batteries is 1mV, and the SOC varies greatly. Therefore, if this method is used to calculate the capacity of lithium iron phosphate battery after cycling, the error will be large.

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