Routing problems in mobile ad-hoc networks (MANET) have been receiving increasing attention in the last few years. Most of the proposed routing protocols concentrate on finding and maintaining routes in the face of changing topology caused by mobility or other environmental changes. More recently, power-aware routing protocols and topology control algorithms have been developed to address the issue of limited energy reserve of the nodes in ad-hoc networks. We consider the routing problem in MANET with the goal of maximizing the life time of the network. We propose a distributed routing algorithm that reaches the optimal (centralized) solution to within an asymptotically small relative error. Our approach is based on the formulation of multicommodity flow, and it allows to consider different power consumption models and bandwidth constraints. It works for both static and slowly changing dynamic networks.