A description is given of a fuel-cell power-supply for mobile phones that operates at room temperature and ambient pressure using liquid methanol and ambient air. The unit is a hybrid system in which a direct methanol fuel-cell (DMFC) and a back-up battery are connected in parallel to meet the power requirements of mobile phones. Electrochemical catalysts for the anode and the cathode of the DMFC are synthesized and Nafion-115 is used as the electrolyte. A 2 M methanol solution is filled in the feed reservoir, and the cathode is exposed to ambient air. Eight unit cells, each having 9 cm(2) of active area, are connected in series in order to raise the output voltage to 2.5-3.9 V, which is the typical voltage range for most mobile phones. Also, to simulate the practical application. an electric circuit is included to increase the output voltage of the back-up battery to repeat the charge.-discharge cycle. During talk mode, the DMFC supplies 10-50% of the required power and the back-up battery supplies the remainder. In standby mode, the DMFC covers 100% of the required power and charges the backup battery.