Provided is a battery pack including a plurality of battery cells, a cell holder that surrounds an accommodation space accommodating the plurality of battery cells and comprises a hollow protrusion formed at a temperature detection position for measuring of the temperature of the battery cells, a cover arranged on the cell holder and having an exposure hole for exposing the hollow protrusion, and a thermistor accommodated in the hollow protrusion through the exposure hole, and a module with various outputs and capacities may be provided in such a manner that a plurality of battery packs, each of which is one unit having the same structure, are connected to each other, and by increasing or decreasing the number of battery packs included in a module, it is possible to provide expandability of the battery pack to adaptively respond to various outputs and capacities by using battery packs having the same structure.