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In this paper the main issues related to the development of electric vehicles utilizing hydrogen fuel cells for on board generation of electric energy are faced and discussed. Two laboratory fuel cell systems (FCS) based on 2.5 and 20 kW H2/air proton exchange membrane stacks were designed, realized and characterized with the aim to elucidate the specific concerns to be considered for automotive applications. The effect of the main operative variables (temperature, pressure and stoichiometric ratio) on stack power and efficiency was experimentally evaluated, while the role of air compressor, fuel purge, stack temperature and humidification strategy in the system management was evidenced. The characterization results were analysed in terms of H2 consumption and available power specifying the energy losses of the individual fuel cell system components. The two fuel cell systems were then used to realize two complete fuel cell power trains with mechanical power of 2 and 30 kW, suitable for scooter and minibus, respectively. The experimental study was conducted on dynamic test benches, able to simulate the behaviour of real vehicles on standard driving cycles, and was focused on the effect of different strategies of energy management, necessary to regulate the power flows inside the power train, on vehicle performance and efficiency. The experimental results suggest some general considerations about the energy management of hydrogen fuel cell propulsion systems. The total efficiency calculated on European R40 driving cycle for the two size power trains was not significantly affected by the control strategy utilized. This can be attributed to the main characteristic of a fuel cell system, that is the negligible influence of load on its efficiency, which is also the main difference with respect to internal combustion engines. Only adopting a load following procedure on a driving cycle characterized by many and long phases of very low load, the total efficiency could be significantly lower than 30% because of minor FCS, efficiency. On the other hand, since the main problem of electric vehicles is constituted by the large and heavy battery packs, necessary to guarantee the required driving range, the use of a load following procedure in a fuel cell power train would permit storage systems to be strongly reduced, with consequent benefits in terms of vehicle habitability and energy consumption. Between the other components of the power train the effect of DC-DC converter on the total efficiency has to be deeply considered. In particular, this component is essential to the correct implementation of any control strategy, and should be specifically designed with respect to the application and carefully matched to the FCS in terms of maximum power and current.