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Fuel-cell vehicles have the potential to revolutionize transportation. In particular, a fuel-cell vehicle using a combined battery-ultracapacitor energy storage system can provide excellent fuel economy and performance while extending the battery life due to more frequent use of the ultracapacitor. This paper first presents a new fuel cell-battery-ultracapacitor (FC-B-UC) vehicle topology. Then, a vehicle simulator is used to show that the new topology is superior to a promising FC-B-UC topology from the literature. Finally, an analytical optimization method is developed to determine the optimal battery and ultracapacitor sizes for two different options of the novel FC-B-UC topology. The optimization method seeks to maximize efficiency and minimize mass and cost of the overall system. Numerical examples are provided to validate the analytical optimization method.