Dynamic voltage scaling (DVS) and dynamic power management (DPM) are the two main techniques for reducing the energy consumption of embedded systems. The effectiveness of both DVS and DPMneeds to be considered in the development of an energy management policy for a system that consists of both DVS-enabled and DPM-enabled components. The characteristics of the power source also have to be explicitly taken into account. In this paper, we propose a policy to maximize the operational lifetime of a DVS-DPM enabled embedded system powered by a fuel cell-battery (FC-B) hybrid source. We show that the lifetime of the system is determined by the fuel consumption of the fuel cell (FC), and that the fuel consumption can be minimized by a combination of a load energy minimization policy and an optimal fuel flow control policy. The proposed method, when applied to a randomized task trace, demonstrated superior performance compared to competing policies based on DVS and/or DPM.