Design And Implementation Of Test System For Lithium Battery Impedance

Lithium-ion battery impedance measurement has important significance for its safe use.This paper focuses on three aspects of system design,implementation,testing and analysis of lithium-ion battery impedance detection system.The working principle and equivalent circuit model of lithium-ion battery are analyzed,the types and sources of noise in the system are described in detail,effective measures to suppress noise are given.In combination with the test requirements,the EIS method is selected as the system measurement method,and gave the overall plan of the system.The hardware circuit of the lithium-ion battery impedance detection system is designed,including control circuit,linear power supply circuit,pre-conditioning circuit,program-controlled excitation source and synchronous sampling circuit.Each circuit structure is analyzed and verified by Multism.The control circuit uses ADu CM3029 and STM32 dual processors.The pre-conditioning circuit includes an AC/DC separation circuit,a band-pass filter,a differential amplification circuit,a DC voltage acquisition circuit,a temperature acquisition circuit,and a power consumption measurement circuit.The synchronous sampling circuit is based on the AD5941 design and integrates ADC,DFT and excitation source output.Lithium-ion battery impedance detection system software was designed,including software design of lower computer,software design of excitation source and software design of upper computer.The Free RTOS operating system was ported to the ADu CM3029 to improve system reliability and set data communication protocols.The PID algorithm was used to calibrate the output of the programmable excitation source.Three methods for identifying system transfer function by frequency characteristic curve are studied: basic Levy identification method,modified Levy identification method and iterative Levy identification method.The human-computer interaction interface was designed using C#,and Matlab components were called to realize functions such as data display,waveform display,threshold alarm and failure analysis.Finally,the whole system and each module are verified by experiments.The experimental results show that the resolution of the differential amplifier circuit is 0.1m Vpp.The DC voltage measurement circuit,temperature acquisition circuit and power acquisition circuit are working normally.The program-controlled excitation source amplitude error is below ± 1%,the frequency error is less than ±1%.By performing FFT analysis on the 100 Hz,1KHz,5KHz,and 10 KHz output signals,the signal-to-noise ratio is below 2%.In the low frequency band identification,the basic Levy identification accuracy is the worst,and the iterative Levy identification accuracy is the best.In the middle and high frequency bands,the identification accuracy of the three identification methods is basically the same,and at the same time,the iterative Levy identification method is used to compare the recognition accuracy under different iteration times.When iterating 300 times,the recognition accuracy is the highest.The system amplitude measurement error is less than ±1%,the phase measurement error is less than ±1%,and the system measurement stability error is less than ±1%...