A major issue in the energy-constrained ad hoc wireless networks is to find ways that increase their lifetime. The communication protocols need to be designed such that they are aware of the battery state. They should also consider the presence of varying sizes and models of the nodes' batteries. Traditional MAC protocols of these networks are designed considering neither the state nor the characteristics of the batteries of the nodes. Major contributions of this paper are: (a) a novel distributed heterogeneous Battery Aware MAC (HBAMAC) protocol, that takes benefit of the chemical properties of the batteries and their characteristics, to provide fair node scheduling and increased network and node lifetime through uniform discharge of batteries, (b) theoretical analysis, using discrete time Markov chains, for batteries of the nodes, and (c) a thorough comparative study of our protocol with IEEE 802.11 and DWOP (Distributed Wireless Ordering Protocol) MAC protocols. © Springer-Verlag 2004.