The effect of amount of AB2 alloy on the hydrogen storage properties of Mg-based composites is investigated. Mg+xwt% Ti 0.1Zr0.9Mn0.9V0.1Fe 0.5Ni0.5 (x ≤ 5, 15, 25, 30, 35, 40, 50, 60 and 75) composites have been prepared by reaction ball milling Mg with Ti 0.1Zr0.9Mn0.9V0.1Fe 0.5Ni0.5 and characterized by powder x-ray diffractograms and scanning electron microscopy. Pressure-composition absorption isotherms of these composites have been obtained in the pressure range 0.1-30bar at 300 °C using the pressure reduction technique. Maximum storage capacity of around 4.8wt% at 300 °C has been achieved in Mg+5wt% Ti0.1Zr 0.9Mn0.9V0.1Fe0.5Ni0.5. The dependence of hydrogen absorption plateau pressure on the unit cell volume of Mg phase in these composite materials is discussed. Thermal desorption of hydrogen has been studied using differential scanning calorimetry. Hydrogen absorption/desorption kinetics of these composites have been performed at 300 °C, and for Mg+25wt% Ti0.1Zr0.9Mn0.9V 0.1Fe0.5Ni0.5 kinetics of absorption have been performed in the temperature range 250-325 °C. The absorption kinetics data have been analysed using rate equations to understand the mechanism of the hydriding reaction process and to obtain the activation energy. © IOP Publishing Ltd.