Methods for Estimating Battery State of Charge

Abstract

The invention discloses a method for estimating the state of charge of a battery, which includes establishing a battery equivalent circuit model; wherein, the battery equivalent circuit model includes a diffusion unit, the diffusion unit is used to characterize the diffusion impedance and includes n-level RC series units, and each level of RC is connected in series The units are connected in parallel at both ends of the capacitive element in the upper RC series unit; the electrochemical impedance spectrum of the battery is measured; the total impedance of the equivalent circuit model is derived in the frequency domain, and based on the measured electrochemical impedance spectrum, the equivalent circuit The value of each component in the model is used for parameter fitting; according to the fitting result, the road terminal voltage U is obtained in the time domain out and battery state of charge SOC, discharge current I t , the relationship at time t, that is, U out =f(I t , SOC, t); measured road terminal voltage U out and discharge current I t , and reversely calculate the state of charge SOC at any time t through the above relationship. Based on the battery equivalent circuit model of the invention, the diffusion phenomenon can be accurately described, the electrochemical impedance spectrum can be matched, and the state of charge can be calculated and estimated relatively accurately in the time domain.

Description

technical field [0001] The present invention relates to the technical field of battery management, and more specifically, to a method for estimating the state of charge of a battery. Background technique [0002] The battery state of charge SOC (State Of Charge) is used to describe the remaining power of the battery. It is an important parameter in the process of battery use. The accuracy of its prediction directly affects the control strategy of the battery management system, thereby affecting the performance of the battery and the performance of the battery. The length of life. Therefore, it is of great research significance to monitor the SOC state of the battery. [0003] Usually, the state of charge (SOC) of the battery is inferred by detecting parameters such as battery voltage, battery current, battery internal resistance, and battery temperature. However, the relationship between the above parameters and SOC will change with the continuous use of the battery, thus ...

AI Technical Summary

Problems solved by technology

The disadvantages are: (1) During the static process of the battery after charging and discharging, and during the alternating charging and discharging process, due to the phenomenon of diffusion, the road terminal voltage will change dynamically, especially when the battery is not discharged, the road terminal voltage will rise. This general model cannot truly describe the above process and the process of the voltage recovery; (2) The impedance spectrum of this general model cannot accurately match the actual electrochemical impedance spectrum measured at both ends of the battery

But its flaw is: due to the Warburg element Z w It is not a basic electrical component, so this model can only describe the impedance change in the frequency domain, and cannot describe the dynamic change of battery charging, discharging and overcharging voltage in the time domain, so it cannot be substituted into the BMS (battery management system) system to calculate SOC

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