Comparative measured and simulated charging and discharging voltages, currents, powers, and times of a vanadium redox flow battery (VRFB)-based energy storage system (ESS) of rated 2.5 kW/6.25 kWh under different values of constant current are demonstrated in this paper. The average mean errors between the measured and simulated voltages and powers of the studied VRFB-ESS under distinct charging and discharging operations can be as low as 2.41%. The rated capacity of the obtained equivalent-circuit model (ECM) of the studied VRFB-ESS is also enlarged to be rated 100 kW/250 kWh to simulate the operating characteristics of a large-scale aggregated equivalent VRFB-ESS model under different constant-current charging and discharging conditions.