-In recent years, Li-ion batteries have been proposed as an essential element for hybrid electrical vehicles (HEV) and electrical vehicles (EV). In such applications, the most possible accurate estimation of the battery states is needed to optimize its operation. Accordingly, battery electrical impedance is known to be able to provide useful states information. Though that electrical impedance spectroscopy has firmly established itself as one of the most informative investigation method especially because of its accuracy, it cannot be easily implemented in embedded systems. In this paper, broadband excitation signals, frequently used in system identification applications, are proposed to perform impedance measurements on a battery cell. Moreover, spectral coherence is an advanced parameter estimated in order to determine the frequency bands where the transfer function of the system is accurately identified. We propose in this study to test and compare the identification performances of such signals for the broadband monitoring of a battery.

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Electrochemical impedance spectroscopy or ac impedance methods are popularly used for the diagnosis of electrochemical generators (batteries or fuel cell). It is now possible to acquire and quantitatively interpret the experimental electrical impedances of such systems, whose evolutions indirectly reflect the modifications of the internal electrochemical process. The scope of these measurement methods is to identify the frequency response function of the system under test by applying a small signal perturbation to the system input, and measuring the corresponding response. Once identified, and according to the application, frequency response functions can provide useful information about the characteristics of the system. Classical EIS consists in applying a set of frequency-controlled sine waves to the input of the system. However, the most difficult problem is the integration of this type of measuring device in embedded systems. In order to overcome this problem, we propose to apply squared pattern excitation signals to perform such impedance measurements. In this paper, we quantify and compare the performance of classical EIS and the proposed broadband identification method applied to a well-known impedance circuit.