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The purpose of this thesis is to establish a dynamic an Ultracapacitor model, including equivalent circuit model, a thermal dynamic model and an aging model. Model parameter identification is conducted based on Alternative Current Impedance Spectroscopy (ACIS) experiment and least squares method to obtain the Ultracapacitor equivalent series resistance (ESR), constant phase element magnitude (Adl), electrolyte resistance (Rel) and constant phase element exponent (γ) at various voltages and temperatures. Various mathematical models are applied to describe the aging process of parameters. The Ultracapacitor aging model is then validated against voltage and temperature measurements under various charge/discharge cycles at nature heat dissipation condition. All the experiment results indicated that the Ultracapacitor aging model is capable of predictions the dynamic behaviors of Ultracapacitor after various periods of aging process.