Electric car power battery SOH measuring and calculating method

Abstract

The invention discloses an electric car power battery SOH measuring and calculating method. Firstly, every single cell is charged fully, and the temperature of the cell is recorded. An ampere hour integral method is used to calculate the accumulated power consumption of every single cell of a current day, and an instant average temperature is obtained through weighted calculation according to the power consumption until the temperature and OCV of every single cell are stable, and then the temperature and OCV of every single cell at the moment are recorded. For each cell, an OCV table is used to search for a corresponding SOC, then a corresponding SOCS at 25 DEG C is obtained, a full charge temperature is used to search for a corresponding SOCF at 25 DEG C of the cell in the table, the power consumption is converted to corresponding power consumption at 25 DEG C, the capacity CSOH of each cell is calculated, and an initial rated capacity C0 is used to calculate SOH = CSOH / C0 for each cell. The method utilizes the stable corresponding relationship between the temperature, OCV and SOC to measure and calculate the SOH of each cell. The test results are accurate and reliable and do not need offline measurement.

Description

technical field [0001] The invention relates to power battery technology, in particular to a method for measuring and calculating the SOH of a power battery of an electric vehicle. Background technique [0002] The power battery pack of electric vehicles, with the increase of use time, the running mileage becomes larger, the number of charge and discharge cycles increases, and the capacity and performance of the battery will gradually degrade. This degree of degradation is measured by an indicator, which is the State of Health of the battery, referred to as SOH. Calculating the SOH can know the various performance changes of the whole battery pack, as well as the degree of differentiation of the battery cells. When a single cell is seriously aging, it can be warned in time to maintain the battery pack and replace the battery cells. [0003] At present, three methods are commonly used to measure SOH. The first method is to take the battery offline and test various parameters...

AI Technical Summary

Problems solved by technology

This method is accurate and reliable, but the disadvantage is that the battery needs to be processed offline and a complete charge-discharge cycle is performed

The second is to measure SOH through internal resistance test, because as the battery ages, the internal resistance of the battery will gradually increase, but there is no clear correspondence between this internal resistance change and SOH

Due to the difficulty of establishing an electrochemical model, this method is difficult to obtain practical application.

Therefore, offline calculation is still the main method at present, which is time-consuming, laborious, and costly. If it is necessary to estimate the SOH of each cell in the battery pack, the cost will be even higher. If the calculation is not performed for each battery, the cell with poor SOH cannot be found in time. Body, timely maintenance and replacement

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