The experimental study of a large scale magnesium hydride tank (10 kg) is presented. In order to enhance thermal exchanges and improve storage time, the MgH2 powder has been compacted with 10 wt.% of Expanded Natural Graphite. An efficient heat exchanger has been designed to transfer the heat from the endo/exothermic sorption reactions to an external heat source/sink through a high temperature heat transfer fluid. An improvement of the loading and discharging time along the first hydrogenation cycles is observed owing to material thermal conductivity modifications. The properties of the cycled material have been studied in order to understand this evolution of the tank behavior. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.