Battery pack for electric power storage device

A battery pack comprising:

• at least one module assembly having at least two battery modules, each battery module including a plurality of unit cells that is stacked in a state in which the unit cells are electrically connected to each other, the at least two battery modules being arranged such that the battery modules are adjacent to each other in a first direction;
• a pair of side plates covering opposite sides of the module assembly, each side plate extending in the first direction;
• a base plate having fastening parts, which are coupled to the side plates, formed at one surface thereof and an external mounting part, which is mounted to an external structure, formed at the other surface thereof, the base plate having a first section with a first width and a second section with a second width, the first width being smaller than the second width and a flange extending upward from the base plate along edges of the first section and second section;
• a sheathing cover coupled to the base plate to cover the module assembly, the sheathing cover having a top wall with a plurality of side edges and side walls integrally connected to and extending from the side edges of the top wall, the side walls extending from the side edges to the base plate to completely cover the pair of side plates;
• and
• a handle comprising a coupling part extending laterally from the first section of the base plate and a grip part extending upwardly from the coupling part, and the grip part spaced in a lateral direction from the side walls of the sheathing cover to create a gap between the grip part and the side walls of the sheathing cover.