The characteristics of an all solid state supercapacitor based on polyaniline (Pani)-Al2O3 coating on aluminium alloy 2024 (Al-2024) surface prepared by the constant current method have been investigated. Three stages are observed in the potential- electrolysis time relation for the simultaneous preparation of the dielectric layer and the conducting polymer on the aluminium foil. The deposition of polyaniline film has been confirmed by cyclic voltammetry. The solid state capacitor has been studied by AC impedance spectroscopy and the capacitive behaviour of the cell is discussed in terms of Nyquist plots, complex capacitance and complex power. The study revealed that the capacitor has comparatively good capacitance, ranging from 450 to 600nF/cm(2), a low time constant and also very low resistance. The normalized reactive power, vertical bar Q vertical bar/vertical bar S vertical bar and active power vertical bar P vertical bar/vertical bar S vertical bar versus frequency plot for the solid state capacitor allow an overview of the whole frequency behaviour of the supercapcitors, ranging from a pure resistance at high frequency to a pure capacitance at low frequency. When a capacitor is used as a source stiffening capacitor and is buffering the supply by delivering initial current, a lower RC time constant allows delivering significantly more current. So this type of solid-state capacitor can be used for the DC-DC converter modules.