BATTERY PACK

Two batteries are made mountable like a cartridge in a housing to achieve the large capacity of a battery pack and to improve the facilitation of operation such as replacement of a battery. The battery pack includes covers 2, 3 having four circumferential lateral surfaces one of which is opened; a lid body 5 opening and closing the opened lateral surface 4 of the housings; and a plurality of batteries 6a, 6b attached into and removed from the inside of the housing. The housing are formed to be divided in two portions one of which is a top cover 2 having the open lateral surface, another one of the two portions being a rear cover 3 mounted with a control substrate mounted thereon. The inside of the top cover is vertically divided in two by a partition plate 8 to form battery-storing portions 9a and 9b which can store the battery cartridges 6a and 6b, respectively.