This paper discusses a decentralized energy management for an engine-generator/battery/ultracapacitor (UC) hybrid energy system with fault tolerance analysis. The energy management problem among the energy suppliers and the load is formed into a non-cooperative power distribution game where the engine-generator, the battery pack, the UC pack, and the load are modeled as independent and related players. Each player has an unique objective, i.e., reducing fuel consumption, prolonging battery cycle life, maintaining UC state of charge and satisfying the load demands, represented by different second order polynomial function based utility functions. In this game, a Nash equilibrium is reached at each control instant to give a balanced solution among players. The weight coefficients in the utility functions can be determined through the Pareto optimal solution a multi-objective genetic algorithm. The fault tolerance analysis based simulation shows that the proposed energy management has a flexible and reconfigurable performance under six different case studies.