In this work, two different supercapacitors manufactured by Eaton Bussman with identical declared capacitance (6 F) but different nominal voltages (2,7 V and 3,0 V) were tested to determine their electrochemical properties. Both supercapacitors have been tested under identical conditions. The methods used to evaluate their electrochemical properties were constant current charging/discharging, cyclic voltammetry and electrochemical impedance spectroscopy. From the results obtained capacitance and internal resistances for both supercapacitors were determined and compared with the declared values. Cyclic voltammograms show approximately rectangular shape, which is characteristic behavior of supercapacitors. Except for the first cycle, cyclic voltammograms obtained in both cases showed no significant change in current with the number of cycles indicating the stability of the supercapacitor. By the method of constant current charging and discharging, it is clear that supercapacitor nominal voltage of 2,7 V has higher values of internal resistance and capacitance compared to supercapacitors of nominal voltage 3,0 V, indicating a different pore size distributions of two tested supercapacitors. The smaller the pores in which the ions penetrate during the charging/discharging, the higher the values of capacitance and energy, and hence increased serial resistance while there is a decline in power density. The electrical and electrochemical properties of examined supercapacitors were determined by electrochemical impedance spectroscopy. All impedance diagrams show similar behavior. However, a supercapacitor with a nominal voltage 2,7 V shows a higher deviation from the capacitive behavior compared to a supercapacitor with nominal voltage 3,0 V, which is reflected in the smaller internal resistance. Based on the results obtained, it is evident that there are no significant deviations from the declared values of the two supercapacitors .