Evaluation method of consistency of lithium ion battery pack for electric vehicle

Abstract

The invention provides an evaluation method of the consistency of a lithium ion battery pack for an electric vehicle, specifically comprising the following steps: A, connecting a battery pack formed by connecting monomer batteries in series with the battery management system of the electric vehicle; B, controlling the battery pack to discharge by the battery management system, and collecting and recording the voltage and the temperature of the monomer batteries as well as the SOC value of the battery pack by the battery management system; and C, in the discharging process, calculating the standard deviation delta of the voltage of monomer battery once every 10% of SOC; according to the value of the standard deviation delta, evaluating the consistency of the battery pack; when the standard deviation delta is less than a preset value, representing that the battery pack has good consistency, otherwise, representing that the battery pack has poor consistency. The computational formula of the standard deviation delta is show in the specification. The evaluation method has the characteristics of simple operation, convenient processing and accurate judgement, and is suitable for evaluating the consistency of the battery pack of the electric vehicle.

Description

technical field [0001] The invention belongs to the technical field of electric vehicle manufacturing, and in particular relates to a method for evaluating the consistency of lithium-ion battery packs of electric vehicles. Background technique [0002] The lithium-ion battery pack of an electric vehicle is composed of multiple single cells connected in series and parallel. However, due to the differences in the performance of each single cell, the performance of the battery pack will decline to varying degrees after a certain charge-discharge cycle. It is manifested in the acceleration of capacity fading and the greater difference in the consistency of single cells in the battery pack, so strict selection must be carried out before the batteries are assembled. If the consistency of the single cells is not good, the charging and discharging process will increase the difference between the single cells, which will easily cause some batteries to be over-discharged or over-charg...

AI Technical Summary

Problems solved by technology

[0002] The lithium-ion battery pack of an electric vehicle is composed of multiple single cells connected in series and parallel. However, due to the differences in the performance of each single cell, the performance of the battery pack will decline to varying degrees after a certain charge-discharge cycle. It is manifested as the acceleration of capacity decay and the greater difference in the consistency of single cells in the battery pack, so strict selection must be made before the batteries are assembled

If the consistency of the single cells is not good, the charging and discharging process will increase the difference between the single cells, which will easily cause some batteries to be over-discharged or over-charged, and the performance of the other part of the batteries will not be fully utilized. It will eventually lead to the deterioration of the performance of the battery pack, and the cycle performance of the battery pack will be attenuated or invalid

[0003] For a well-assembled battery pack, how to verify the cycle performance of the battery pack is very important. At present, the existing battery consistency evaluation methods are all for single cells, but for the consistency of high-voltage, large-capacity battery packs However, there is currently no unified means and method for evaluating

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