This article presents results of a characterization study undertaken on a Mg-Fe-Mn-Ni alloy for hydrogen storage application. This Mg-Fe-Mn-Ni alloy undergoes rapid activation in less than five charging/discharging runs and is able to reversibly uptake 5 mass% H2. The charging/discharging characteristics of this alloy are evaluated as a function of temperature. The optimal temperatures for hydriding and dehydriding are identified as 325.5 degrees C and 372 degrees C, respectively. The kinetics data are fitted to lumped first-order reaction models as well as to a spherically symmetric diffusion model with first-order kinetics. Based on the analysis, model constants are derived. Further, based on the van t Hoff equation, the formation enthalpy and entropy are determined as 65 +/- 3.1kJ/mole and 101 +/- 4.7J/mole K, respectively.