On the design of multisine signals for maintaining stability condition in impedance spectroscopy measurements of batteries

Abstract

For measuring the impedance spectra of batteries, several challenges should be overcome to maintain the stability condition, especially at low frequencies in the mHz range. Even if the sine sweep signals realize the highest signal power, they lead to a severe stability problem at low frequencies in the mHz region. In this paper, we propose a novel design method for multisine excitation signals, which reduces measurement time and maintains battery stability. The novel excitation signals are structured in a dummy interval for considering the transient behavior of the battery and three folds of a multisine signal with an optimized crest factor, frequency bins, and measurement time. The system stability is evaluated by a consistency check based on the Linear Kramers–Kronig (LKK) method. The results show that the novel excitation signals outperform the often-used sinusoidal sweep signals by maintaining the stability condition during impedance measurements even at low frequencies in the mHz range. For example, for a signal with six frequencies/decade from 10 mHz to 1 kHz, a root means squares error of the LKK of 31.70 ppm could be realized instead of 201.21 ppm for the sine sweep, and the measurement time could be reduced to 315 s from 1440 s.