In the frame of SPACT-80 project to design and manufacture a robust and durable air/hydrogen 80 kWe PEM fuel cell for transportation application, experiments have been carried out on various electrode active surfaces since the full scale system could be damaged by some particular operating conditions. Thus, the main objective of this paper was to verify that a 25 cm 2 single cell, a 5-cell pilot stack and a 90-cell stack exhibit the same behaviour and that they are representative of the full device's performance. After a brief description of the studied device the scaling up effect was checked. In non-optimal conditions, experiments were mainly conducted on single cell and pilot stack. In driving cycle and when studying various gas flows, they present similar evolution for the cell voltage as well as for the water management. The water transport coefficient and the diffusion resistance values determined by impedance spectroscopy highlight the presence of liquid water that could have an effect on the gas transport to the electrode. Investigation on the air humidification conditions shows that at lower relative humidity (RH), the two fuel cells have similar behaviour but above 60% RH different evolutions appear. Whatever the air humidification conditions, liquid water is present in both compartments. (c) 2008 Elsevier B.V. All rights reserved.