Traditional low power design minimizes the total power consumption. However for systems that want to maximize co-operation life time among the battery-powered devices, the total power minimization strategy may not be the best. The workload allocation among these devices has a dramatic impact on the co-operation life time. In this paper, we address this problem by formulating it as a linear programming (LP) problem. A simplified energy-aware algorithm is proposed to provide the optimal solution according to the energy capacity ratio of the devices. This algorithm is simple enough to be embedded into real-time system and we illustrate this by an example using a configurable transmitter-receiver pair. Experimental results show that the proposed algorithm significantly outperforms the other workload allocation strategies by 400.66% in the randomly-generated systems and 23.20% in a point-to-point (P2P) communication system, respectively