Lithium battery state of charge (SOC) estimation method

Abstract

A lithium battery state of charge (SOC) estimation method is used for lithium battery energy storage equipment with a micro controller and a storer and used for correction of practical capacity of a lithium battery. The method comprises the following steps: utilizing an electromotive force method to establish a battery circuit model; determining the functional relationship between the electromotive force and the SOC; calculating the current SOC number value according to the obtained relationship between current and voltage; accurately calculating the original value SOC0 of the SOC according to the relationship between current and voltage; calculating the current SOC value by using a current integration in a real time manner; correcting the estimation values obtained through the electromotive force method and the current integral mensuration by using an expanded Kalman model; realizing real-time on-line accurate estimation for battery packs by using expanded Kalman filtering circular iterative computations.

Description

technical field [0001] The invention relates to a battery management system, in particular to a method for estimating the state of charge of a lithium battery. Background technique [0002] With the increasingly prominent problems of environmental protection and energy saving, due to the advantages of high specific energy and green environmental protection, lithium-ion batteries, as large-capacity power sources, have gradually been applied in the fields of automobiles, aerospace, and ships. The energy density of lithium-ion batteries is getting higher and higher, the capacity is getting bigger and bigger, and the number of battery cells connected in series is also increasing. During the long-term use of the battery pack, due to the consistent Poor performance causes overcharge and overdischarge of one or several batteries, which in turn causes performance degradation of the entire battery module, insufficient capacity, or even failure, which seriously affects the service lif...

AI Technical Summary

Problems solved by technology

[0004] At present, the accuracy of the SOC estimation of the battery management system is not high. The problems encountered in the application of the current integration method are: the power battery may start working at any SOC. If there is an error in the initial SOC, then this error cannot be eliminated. Yes, because the current integration method is a pure integral link, the pure integral link itself cannot eliminate the error caused by the initial value

Moreover, due to inaccurate current measurement, it will cause SOC calculation errors, which will accumulate over a long period of time, and the errors will become larger and larger; in the case of high temperature conditions and severe current fluctuations, the errors will be even greater

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