We consider large population of interacting mobile devices with individual state dynamics. Each mobile device has its own battery. The battery state is a modeled as a Markov decision process. The mobile devices are coupled via their payoff functions. Each mobile chooses a dynamic power management strategy in order to have a satisfactory long-term payoff. We propose a mean field stochastic game formulation when the number of mobile devices is very large. We establish a connection between finite stochastic game modeling and the evolutionary game modelling at the infinite population. Sufficient conditions for stationary mean field equilibria are given.