This paper introduces a flexible moisture-powered supercapacitor (mp-SC) capable of self-charging and voltage stabilization using atmospheric moisture. The mp-SC integrates a polyelectrolyte-based moist-electric generator (MEG) and a graphene electrochemical capacitor (EC). The device demonstrates a self-charged high areal capacitance of 138.3 mF cm² and maintains 96.6% voltage for 120 hours. A large-scale device (72 mp-SC units) achieves a self-charged 60 V, powering various commercial electronics.