The assignment in this paper was to test commercially available supercapacitor and to prepare and test supercapacitor assembled in the lab from the active carbon as an electrode component. The aim of this paper was to compare the electrochemical properties of a commercially available supercapacitor and a prepared supercapacitor with the behaviour of an ideal supercapacitor. Both supercapacitors were tested by cyclic voltammetry, galvanostatic charging/discharging and electrochemical impedance spectroscopy. Cyclic voltammetry was performed in the potential range from 0,050 V to 2,500 V at scan rate of 20 mV s^-1 with three repetition cycles. Galvanostatic charging/discharging was performed at a constant current of ±100 mA for a commercial supercapacitor with 100 repetition cycles and at the current of ±10 mA for a prepared supercapacitor with 99 repetition cycles. Electrochemical impedance spectroscopy was performed at 0,050 V, 1,250 V and 2,500 V in the frequency range 50 kHz -100 mHz with 6 points per decade and an amplitude of alternating voltage of 20 mV. Commercial supercapacitor showed much lower internal resistance than the prepared supercapacitor. Both supercapacitors showed typical capacitive behaviour and the existence of differential capacitance was identified. The slowest stage in the charging and discharging process for commercial supercapacitor is the diffusion of ions. For the prepared supercapacitor the slowest stage is charge transfer visible as kinetic effects.