Five different active carbons obtained by OVIA inovacije d.o.o. were used in making slurries for supercapacitor electrodes to compare their supercapacitive properties based on various electrochemical tests. The tested active carbons were prepared by various mechanical and thermal treatments of the original active carbon produced by the company T.T.T. d.o.o, Croatia. The cyclic voltammetry plots for all materials exhibited capacitive behavior except for the sample additionally activated with KOH and annealed at 700°C. Two samples, one pretreated in microwave oven in air and one pretreated in the furnace in the inert atmosphere show a slight indication of additional pseudocapacitive properties. The Nyquist plots of all samples have a high-frequency semicircle originating from kinetic hindrance and a low-frequency capacitive vertical line. The graphs show an increase in the diameter of the semicircle for the original material and the one pretreated in the microwave oven after subjecting these supercapacitors to 30 cycles of charging and discharging indicating interfacial deterioration in these supercapacitors. Charge/discharge tests for all materials exhibited triangular curves at studied current density, indicating the absence of faradic reactions. The supercapacitor fabricated from microwave treated original active carbon yielded the highest specific capacitance Cs determined from both CV and EIS test at 27.31 F g^-1 and 24.46 F g^-1 respectively, while the active carbon pretreated in the furnace recorded the highest specific capacitance from GCD test with a value of 30.27 F g^-1. General comparison of the Cs values from the three tests shows that the values derived from CV and GCD tests are closer in comparison to the values from EIS test. FTIR analysis indicated the presence of oxygen groups that generally influence the electrochemical performance of supercapacitors. The DLS analysis shows that there are two particle sizes in the sample additionally activated with KOH and annealed, and the one pretreated in the microwave oven, while other active materials have single particle size. the original material and the one pretreated in the microwave oven are significantly similar over a range of temperatures in terms of thermal stability. The sample additionally activated with KOH and annealed is the active material with the least desirable properties among studied materials.