Parallel lithium ion battery pack virtual connection and internal resistance increase fault identification method

Abstract

The invention provides a parallel lithium ion battery pack virtual connection and internal resistance increase fault identification method. The battery pack is formed by connecting n single batteriesin parallel, the parallel battery pack is regarded as a battery, and the total current, tab voltage, total voltage and surface temperature of the battery are recorded. The battery impedance is identified on line based on the equivalent circuit model and recursive least square, and if the battery impedance is greater than a threshold value, it is determined that an impedance increase fault exists.The impedance standard deviation is further calculated, if the impedance standard deviation is greater than the threshold and the duration is greater than the preset time, it is determined the fault is virtual connection, and otherwise, it is determined that the internal resistance is increased. If the tab voltage of the battery i is lower than that of other batteries during charging and higher than that of other batteries during discharging, the battery i is in virtual connection; and if the battery i does not exist and the temperature of the battery j is higher than that of other batteries,the internal resistance of the battery j is increased. When the temperature difference between the batteries is greater than 5 DEG C, it is determined that a first-stage fault occurs. Identification,positioning and grading of virtual connection and internal resistance increase faults of the parallel battery pack can be realized.

Description

technical field [0001] The invention relates to the technical field of lithium-ion battery packs, in particular to a fault identification method for virtual connection and internal resistance increase of parallel lithium-ion battery packs. Background technique [0002] In order to meet the power output requirements of electric vehicles, electric vehicle battery packs often need to be composed of several large-capacity battery cells connected in series and in parallel. However, a series of factors such as equipment defects and driving conditions may cause the virtual connection and internal resistance between batteries to increase. Virtual connection refers to poor contact or loose connection between batteries, which increases the contact resistance between two battery cells and increases the Joule heat generated on the connector; increased internal resistance means that the internal resistance of the battery itself increases, which makes The electrochemical heat generation ...

AI Technical Summary

Problems solved by technology

[0004] The purpose of the present invention is to solve the problem that the virtual connection and internal resistance increase faults cannot be distinguished in parallel battery packs, and proposes a method of collecting battery tab voltage and total voltage, based on the equivalent circuit model (ECM) and the recursive least squares method ( RLS) realizes the method of virtual connection and internal resistance increase fault identification, location and classification of parallel battery packs

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