Battery pack and motor-driven tool using the same

A battery pack comprises a housing 11, 16 with an opening 16c through which a protective member for a plurality of first terminals of an electric apparatus is inserted; a board 13 with a terminal arranging part 13A; a plurality of second terminals 14 positioned in the housing and adapted to be engaged with the first terminals; and a cover 15 covering an area of the board between the terminal arranging part and the opening, wherein the plurality of second terminals includes a terminal with positive polarity and a terminal with negative polarity, and the cover is provided with a protuberance 15C between the terminal with positive polarity and the terminal with negative polarity.