In this paper, experimental results obtained on a small size fuel cell power train (1.8 kW) based on a 500 W proton exchange membrane (PEM) stack are reported and discussed with specific regard to energy management issues to be faced for attainment of the maximum propulsion system efficiency. The fuel cell system (FCS) was realized and characterized via investigating the effects of the main operative variables on efficiency. This resulted in an efficiency higher than 30% in a wide power range with a maximum of 38% at medium load. The efficiency of the overall fuel cell power train measured during both steady state and dynamic conditions (European R40 driving cycle) was about 30%. A discussion about the control strategy to direct the power flows is reported with reference to two different test procedures used in dynamic experiments, i.e., load levelled and load following. (c) 2006 Elsevier Ltd. All rights reserved.