Cell characteristics for 46Ah High Power Kokam Nano Pouch Cell
Description
A 46Ah cell was characterised by Electrochemical Impedance Spectroscopy (EIS) for parameterisation of a R-RC-RC equivalent circuit model. Samples were measured for all combinations of temperature (0, 10, 20, 30, 40°C) and state of charge (0, 10, 20, …, 90, 100%). The raw data was analysed by the Matlab extension DRTools to identify the most dominant time constants. Using both biggest and smallest time constant one parameter set (R1/C1, R2/C2) was calculated. In addition, interpolating the zero-crossing point of the imaginary impedance give the parameter R. SciPy's optimiser "L-BFGS-B" was then used with the DRT data as initial guess to fit the model onto the data. For this, the Euclidean distance between model impedance and measured impedance in the Nyquist plot was minimised. Due to the limitations of the model used, measurement points with positive imaginary impedances were not considered during the fitting process. The cell was characterised by galvanostatic EIS measurement in the frequency range [10mHz to 100MHz] with a current of 1A. Per decade ten measurements were logarithmically distributed. This dataset was created during a study on detection possibilities of cell faults thankfully funded by the European Automobile Manufacturers' Association (ACEA).