A Study of Binary Excitation Sequences for use in Battery Impedance Spectroscopy

Excitation signals are crucial in defining the duration and quality of the final impedance spectrum measurement. Conventionally, impedance spectroscopy is carried out using a sine frequency sweep or a multisine. However, for measurement systems where only a binary excitation is possible, such as online DC/DC converters, the choice of the excitation signals becomes very limited. This paper compares several binary excitation sequences for Li-ion battery diagnosis and different binarization methods of multisine. It is shown that impedance spectra based on Multifrequency Binary Sequences (MBS) optimized by Evolutionary Role Playing Game Theory crest factor optimization method and based on Sign or
$\Delta\Sigma$
modulation outperform those made using PRBS or chirp signal, owing to their 14x higher SNR. Linear Kramers Kronig was used to check the deviation, showing that MBS-Sign has an RMS deviation of 53.69 ppm, followed by MBS
$A\Sigma$
at 89.39ppm, then MBS PWM at 145.41 ppm, then signum chirp at 0.51 % and finally PRBS at 1.51 %. Therefore MBS based on sign, whose result is very comparable to multisine's, is recommended for Li-ion battery diagnosis