基于EIS的单体电池内阻精确测量系统

Accurate single battery internal resistance measuring system based on EIS

以STM32为硬件核心,采用电化学阻抗谱(EIS)法,以频率为20Hz、幅值恒定的信号作为激励,注入电池。通过脉冲宽度调制(PWM)技术微调激励信号的频率,使注入的激励信号的幅值和流出电池的电流信号幅值趋于相等,减小直流系统中分布电容对测量结果的影响,再以每周波256点的采样率采集电池的电流和电压,并进行快速傅里叶变换(FFT)运算和小波变换得到电池的内阻。与电池测试仪的测试结果相比,测量误差均在±0.1mΩ左右(不含测量导线阻值),且测得的各单体电池之间的内阻差异较小,验证系统的精确度和有效性。

With STM32 as hardware core,electrochemical impedance spectroscopy(EIS)method was used to inject the battery with the signal of 20 Hz and constant amplitude as excitation.The frequency of the excitation signal was fine-tuned by pulse width modulation(PWM)technology,so that the amplitude of the excitation signal injected and the current signal flowing out the battery tended to be equal,the influence of the distributed capacitance in the DC system on the measurement results was reduced.The sampling rate of 256 points per cycle was used to collect the current and voltage of the battery.Then fast Fourier transformation(FFT)and wavelet transform were performed to get the internal resistance of the battery.Compared with the test results of the battery tester,the measurement errors were all around ±0.1 mΩ (measure wires resistance was removed),the difference of measured internal resistance between each cell was small,which verified the accuracy and effectiveness of the system.