Uncertainty Characterization of a Practical System for Broadband Measurement of Battery EIS

Electrochemical impedance spectroscopy (EIS) is of fundamental importance for the characterization and monitoring of rechargeable batteries in the automotive, energy storage, and electronics sectors. In this paper, a low-complexity practical system for electrochemical impedance spectroscopy of batteries is presented and the uncertainty associated with its measurement results is analyzed. The system is based on a voltage-controlled current generator and on the acquisition of current and voltage signals from the battery under test. Arbitrary current waveforms can be generated, thus the system is flexible and reconfigurable. In particular, a broadband multisine excitation signal is used, enabling faster measurements with respect to the conventional stepped-sine approach. The proposed system is characterized by repeated measurements on a 18650 lithium-ion battery. Moreover, it is validated by comparison with a commercial benchtop instrument, and with the ground-truth provided by a discrete-component Randles circuit. Results show that the system is able to accurately and repeatably measure the impedance of a battery in a wide frequency range from 0.05 Hz to 1 kHz. Furthermore, it provides results that are consistent with the commercial instrument and with the ground truth of the R-C Randles circuit. Therefore, the proposed system using the broadband multisine method is suitable for implementing fast and inexpensive monitoring capabilities in smart battery management systems.