Electrochemical Impedance Spectroscopy of Li-Ion battery on-board the Electric Vehicles based on Fast nonparametric identification method

Electrochemical Impedance Spectroscopy (EIS) is commonly used for the diagnosis of electrochemical energy accumulators, for example Li-Ion batteries in Electric and Hybrid Vehicles. Measuring the impedance in a wide frequency range, it is possible to investigate on the modifications of the internal electrochemical cell process, evaluating its current state of life. EIS test consists of the excitation of the battery, or cell, with a defined current signal, and then measuring the cell voltage, the frequency response of the system is computed. The classical EIS test, based on the excitation with a frequency controlled sine wave in input, requires expensive instruments and long time test procedures; therefore it has many problems on the integration on the embedded systems. In this paper, a pseudo random square signal, which shows a simply hardware implementation, is used as excitation signal input on the cell for the impedance evaluation. The effectiveness of the method has been validated based on simulation test, in order to obtain good results in terms of impedance estimation accuracy, minimizing time duration and energy consumption.