A low-cost Electrochemical Impedance Spectroscopy-based sensor node for online battery cell monitoring

This paper proposes a proof-of-concept for a low-cost compact battery cell monitoring system based on Electrochemical Impedance Spectroscopy (EIS). The architecture exploits a multisine excitation signal, which reduces the time required for EIS measurement in the frequency range of interest, enabling online battery monitoring/diagnosis. A comprehensive CAD simulation of the system is performed in TINA-TI to evaluate its performance. The simulation covers the analysis of the general behaviour of the entire system and the complete signal elaboration flow, from analog signal processing to digital analysis of the impedance data based on Discrete Fourier Transform (DFT). This allowed for the analysis of the non-ideal effects of the components, as well as the error induced by the DFT algorithm. Moreover, thermal-noise limitation on the resolution of the system is assessed to verify its capability of detecting variations down to 1 mΩ. Finally, the system is tested in the reconstruction of the impedance spectrum of a battery cell described by an integer-order equivalent circuit model, demonstrating good accuracy. The overall system is realized with low-power off-the-shelf components, representing an innovative solution towards the feasibility of an even more integrated sensor node, which will be designed for implementation at cell level for in-operando sensing.