Ad hoc networks, and particularly sensors networks, are composed of nodes in which the batteries and processing capacities are limited. Each node can adjust its power to some extent, that determines all its neighbors that can potentially participate in a hop. The traffic expedition through multiple hops is used when the foreseen destination is not in the immediate extension. The nodes have initially limited energy and consume it in different proportions, according to power level and foreseen receivers. In this paper, a new approach to choose the data paths is proposed, in order to maximize the lifetime of node batteries. This algorithm, basically inspired from project management theory, is simple and allows to find the longest life time of an ad hoc network by calculating the optimal path between a source and a destination.