The rapid developments in the field of electrochemistry, enabled lithium-ion batteries to achieve a very good position among all the other types of energy storage devices. Therefore they became an essential component in most of the modern portable and stationary energy storage applications, where the specific energy and the life time play an important role. In order to analyze and optimize lithium-ion batteries an accurate battery model for the dynamic behavior is required. At the beginning of this paper four different categories of electrical models for li-ion cells are presented. In the next step a comparison between equivalent circuit diagrams and fractional rational functions with the complex variable s is shown for lithium-ion battery modeling. It is described how to identify the parameters of the models in the time domain and also in frequency domain. The validation of the different models is made for high and low dynamic current profiles. In the first step the dependency of all model parameters on the temperature and on the battery age is neglected. These effects will be taken into account in the continuation of this work
 Huria, T.; Ceraolo, M.; Gazzarri, J.; Jackey, R., "High fidelity electrical model with thermal dependence for characterization and simulation of high power lithium battery cells," Electric Vehicle Conference (IEVC), 2012 IEEE International , vol., no., pp.1,8, 4-8 March 2012
 Min Chen; Rincon-Mora, G.A., "Accurate electrical battery model capable of predicting runtime and I-V performance," Energy Conversion, IEEE Transactions on , vol.21, no.2, pp.504,511, June 2006
 M. Montaru and S. Pelissier, "Frequency and Temporal Identification of a Li-ion Polymer Battery Model Using Fractional Impedance," in Les Rencontres Scientifiques de l'IFP - Advances in Hybrid Powertrains, Rueil-Malmaison, France, November 2008.
 S. Buller, M. Thele, E. Karden and R. W. De Doncker, "Impedancebased non-linear dynamic battery modeling for automotive applications," Journal of Power Sources, vol. 113, no. 2, pp. 422-430, 27 January 2003.
 Buller, S.; Thele, M.; De Doncker, R.W.A.A.; Karden, E., "Impedancebased simulation models of supercapacitors and Li-ion batteries for power electronic applications," Industry Applications, IEEE Transactions on , vol.41, no.3, pp.742,747, May-June 2005
 Al Jed, H.; Mieze, A.; Vinassa, J. -M; Simon, R., "Mathematical modeling of aging factors for Li-ion battery cells," Vehicle Power and Propulsion Conference (VPPC), 2010 IEEE , vol., no., pp.1,4, 1-3 Sept. 2010
 G. L. Plett, "Extended Kalman filtering for battery management systems of LiPB-based HEV battery packs Part 1. Background," Journal of Power Sources, p. 252-261, 2004.
 G. L. Plett, "Extended Kalman filtering for battery management systems of LiPB-based HEV battery packs Part 2. Modeling and identification," Journal of Power Sources, p. 262-276, 2004.
 Farag, M. S.; Ahmed, R.; Gadsden, S.A.; Habibi, S.R.; Tjong, J., "A comparative study of Li-ion battery models and nonlinear dual estimation strategies," Transportation Electrification Conference and Expo (ITEC), 2012 IEEE , vol., no., pp.1,8, 18-20 June 2012
 A. Rahmoun and H. Biechl, "Parameters Identification of Equivalent Circuit Diagrams for Li-Ion Batteries," in 2012 11th International Symposium PÄRNU, PÄRNU, Estonia, 2012.
 X. Hua, S. Li and H. Peng, "A comparative study of equivalent circuit models for Li-ion batteries," Journal of Power Sources, p. 359-367, 2012.
 D. Andre, M. Meiler , K. Steiner, H. Walz, T. Soczka-Guth and D. U. Sauer, "Characterization of High-Power Lithium-Ion Batteries by Electrochemical Impedance Spectroscopy. II: Modelling," Journal of Power Sources, p. 5349-5356, 15 June 2011.
 Biechl, H.; Lorenzen, H. W.; Lubasch, R.; Prenner, H., "Transient Behaviour of a Current-Source Inverter-Fed Synchronous Motor with a Solid Rotor," Power Engineering Review, IEEE , vol.9, no.9, pp.52,52, Sept. 1989
 H. Biechl and H. Bischof, "Meßtechnische Ermittlung von Systemübertragungsfunktionen aus transienten Übertragungsverläufen von Systemanregung und - antwort - Anwendung auf Synchronmaschinen," etzArch.10, pp. 47-51, 1988 (in German).
 O. Obeidi and H. G. Schweiger, "Impedance Spectra of Lithium Ion Cells Influence of Temperature, State of Charge and Ageing," in Kronacher Impedanztage 2011, Kronacher, Germany, 2011.