The need for greener energy sources their storage, management and monitoring, are at the core of research around the globe. This paper focuses on the first step of developing an embedded system that is capable of conducting fast online impedance spectroscopy of batteries for integrated monitoring throughout the battery life cycle in real-world industrial and residential applications such as electric vehicles, energy storage systems in energy grids etc. It significantly covers the experimental methodology to conduct online EIS data its treatment and conversion into the frequency domain by Fast Fourier transformation. Selection of an equivalent circuit model to define various electrochemical characteristics of Li-Ion batteries. Further, it describes the exploitation of EIS data by an optimisation algorithm to estimate the parameters of equivalent circuit model closely resembling that to Li-battery, accuracy between various optimisation methods is compared. Finally, the proposed online EIS-ECM modelling methodology is validated by experimental tests and the results prove the capability of the test bench to design and evaluate monitoring methodology before their embedded implementation.