A lithium ion battery discharge process voltage inconsistency estimation method and device

Abstract

The invention provides a method and a device for estimating voltage inconsistency in a discharging process of lithium ion batteries. The method comprises the following steps of: obtaining a probability distribution cloud picture of battery discharging voltage changing along with capacity before battery grouping; solving a first-order derivative and a second-order derivative about voltage relativeto capacity for the probability distribution cloud picture; and according to the first-order derivative and the second-order derivative, obtaining a change rule of discreteness and symmetry of voltagedistribution of the single batteries along with a discharge process. The method not only can estimate the voltage discreteness change process, but also can estimate the voltage symmetry change process, an estimation result can effectively guide establishment of a battery pack state estimation algorithm, it is guaranteed that each single battery in the battery pack is within a monitoring range, and monitoring dead angles are avoided. According to the method, the first derivative and the second derivative of the voltage relative to the capacity are obtained by adopting a numerical derivation method, and the voltage discreteness and symmetry are directly obtained, so that a complex statistical method is effectively replaced, and high-efficiency prediction of discharge voltage inconsistency is realized.

Description

technical field [0001] The invention relates to the technical field of lithium ion batteries, in particular to a method and a device for estimating voltage inconsistency in the discharge process of lithium ion batteries. Background technique [0002] In order to meet the needs of high-energy and high-power vehicles, lithium-ion batteries need to be connected in series and parallel to be used in vehicles. However, due to the difference in performance between the single cells, the performance of the battery pack is lower than that of the single cell, which will not only affect the detection accuracy of the BMS, but also shorten the life of the battery pack or cause safety problems. The problem of inconsistency after single cells are grouped is inevitable and will only increase with the cycle process. The most important manifestation of inconsistency between cells in the battery pack is the inconsistency of voltage and capacity, which will directly affect the accuracy of the b...

AI Technical Summary

Problems solved by technology

The problem of battery inconsistency caused by the production process can be alleviated to a certain extent by screening methods, but there is still a lack of comprehensive understanding of the problem of battery inconsistency after grouping

This will affect the long-term detection accuracy and working condition control of the battery pack, making individual batteries become monitoring dead spots in the battery pack, unable to work under normal working conditions, causing accelerated aging or safety issues

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