Optimized mixed-domain signal synthesis for broadband impedance spectroscopy measurements on lithium ion cells for automotive applications

Abstract

Abstract. A new impedance spectroscopy measurement procedure for automotive battery cells is presented, which is based on waveform shaping. The method is optimized towards a short measurement duration, high excitation power and increased frequency resolution and overcomes limitations of established methods. For a given spectral magnitude profile, a corresponding time domain waveform is derived from the inverse discrete Fourier transform. Applying an identical initial phase angle for each frequency component, the resulting signal exhibits a high peak-to-peak amplitude at relatively low total excitation power. This limits the maximum allowed power for quasi-linear excitation. Altering the phase angles randomly spreads the excitation power across the complete measurement duration. Thereby, linearity is preserved at higher excitation power. A large set of phase patterns is evaluated statistically in order to obtain a phase pattern with a significant peak-to-peak amplitude decrease. By means of numerical optimization, even further peak-to-peak amplitude reduction is achieved. Including window functions in the synthesis concept minimizes spectral leakage without compromising the spectral signal magnitude in the frequency range of interest. A time domain waveform optimized for impedance spectroscopy on lithium ion cells is synthesized based on the proposed approach and evaluated on real automotive cells. The resulting impedance data show good concordance with established standard measurement procedures at significantly reduced measurement duration and charge throughput. Additionally, increased frequency resolution is achieved, enhancing the level of detail of the obtained impedance data. The method is used for improved localization of aging effects in the cells, without further stress of the cells by the measurement procedure.

Design of a Wireless Charging System for Online Battery Spectroscopy

“…Nevertheless, these experimental results were obtained by using expensive facilities and long-time test procedures. Rapid and real-time EIS methods have been proposed in the last years: [15][16][17][18][19][20][21][22][23][24][25][26] propose the identification of battery impedance in a defined frequency band through broadband current signal excitation. Periodic broadband signals exhibit a lower crest factor [27].…”

Electrical impedance spectroscopy (EIS) for biological analysis and food characterization: a review

“…These equations can be used to calculate the KK residuals and test the data for linearity for increasing amplitudes of the stimulating signal (Lohmann et al, 2015;Haußmann and Melbert, 2017) in order to choose the best LTI-compliant signal-to-noise ratio. However, Eqs.…”

Crest Factor Optimization for Multisine Excitation Signals with Logarithmic Frequency Distribution Based on a Hybrid Stochastic-Deterministic Optimization Algorithm

“…A time profile of the multisine optimized by the proposed method is shown in Figure 10. The signal is normalized to [−0.8 A, +0.8 A] to assure a high signal-to-noise ratio but with enough stability [14]. This allows a maximum change in SoC of 0.03% so that the stability of the battery is kept quasi-constant during the measurement, as shown in Figure 11.…”

“…Spectra measurements covering the frequency range from mHz to kHz can take fifteen minutes to several hours to measure. Multi-frequency signals provide a better alternative, help shorten the measurement time, and increase the accuracy for the same frequency range as the frequency sweep signals [13,14]. Among multi-frequency signals, multisine has been preferred because it has a high signal-to-noise ratio and realizes a good excitation energy per frequency.…”