Method and device for calculating state of charge of battery pack

Abstract

The present invention proposes a method for calculating the state of charge of a battery pack, the calculation method comprising: obtaining the current state of charge and the current test temperature of the battery cells in the battery pack; according to the current state of charge, the current test temperature and the preset AC impedance relationship table and preset compensation voltage relationship table to obtain the current AC impedance and current compensation voltage; calculate the estimated voltage of the battery cell according to the current state of charge, current AC impedance and current compensation voltage; calculate the voltage difference between the estimated voltage and the test voltage; The voltage difference obtains the correction formula that the current state of charge, the current AC impedance and the current compensation voltage satisfy, and obtains the corresponding correction value according to the correction formula; performs correction according to the correction value; obtains the charge of the battery pack according to the current state of charge after the correction of the battery unit power state. The calculation method of the invention can reduce the cumulative error and improve the calculation accuracy of the state of charge of the battery. The invention also provides a calculation device for the state of charge of the battery pack.

Description

Technical field [0001] The present invention relates to the field of vehicle technology, and in particular to a method and device for calculating the state of charge of a battery pack. Background technique [0002] Lithium batteries are commonly used energy supply devices in electric vehicles. Improving the estimation accuracy of the state of charge (SOC, State of Charge) of lithium batteries is a research hotspot in the battery field. The accuracy of the SOC of lithium batteries is used in the control algorithm of hybrid vehicles. And the safety and economy of pure electric vehicles are of great significance. The current SOC estimation methods of lithium batteries used in electric vehicles mainly include discharge test method, internal resistance method, open circuit voltage method, load voltage method, ampere-hour measurement method, neural network method and Kalman filter method. Among them, the ampere-hour measurement method passes the load Current integral estimation of SOC...

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Problems solved by technology

[0003] However, the ampere-hour metering method is an open-loop prediction method. Although the accurate estimation of the power can be realized in a short period of time, as the cumulative error increases, the estimation accuracy will become worse and worse. The battery parameters will change accordingly due to changes in factors such as the increase of the

Therefore, the indeterminate quantization of constants and errors in the calculation formula used for SOC estimation leads to inaccurate estimation of battery SOC

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