An enhanced model of a PEM electrolyser cell is presented, based on linked modular mathematical models of the anode, cathode, membrane and cell voltage. In addition to predicting the overall equilibrium electrolyser cell performance, based on parameters related to the materials of construction and the configuration of its components, the model is a powerful tool for exploring control strategies and understanding the contributions to cell voltage from the various internal components as a guide to researchers aiming for improved performance. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.