A battery pack with a device for locking said battery pack to a cordless power tool has a guide configured to guide the battery pack in a predetermined movement direction as it moves between a locking position in which it is locked to the cordless power tool and a removal position in which it is removed from the cordless power tool, the guide has a break in at least one location between the locking position and removal position, and at said location a force acting on the battery pack moves the battery pack into a safety position offset from the guide, in which the battery pack is prevented from moving further along the guide into the removal position.