Polymer Electrolyte Membrane Fuel Cell (PEMFC) portable power generators are gaining importance in emergency applications. In this study, an air-cooled PEMFC stack was designed and fabricated for net 500 W power output. Gas Diffusion Electrodes (GDE's) were manufactured by ultrasonic spray coating technique. Stack design was based on electrochemical data obtained at 0.60 V was 0.5 A/cm(2) from performance tests of a single cell having the same membrane electrode assemblies (MEA) that had an active area of 100 cm(2). Graphite bipolar plates were designed and machined by serpentines type flow. The stack comprising of 24 cells was assembled with external fixing plates. The stack temperature was effectively regulated by the cooling fan based on on-off control system. A maximum power of 647 W was obtained from the stack. The PEMFC stack was stable during start-up and shutdown cycling testing for 7 days at 65 degrees C in H-2/air at a constant cell voltage. Copyright (c) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.