Tool batteries

A tool battery (10) includes a plurality of battery cells (C) and a holder device (30). The holder device (30) includes a pair of holder members (32) and a plurality of lead plates (36, 37) mounted to each of the holder members (32). Each of the holder members (32) has fitting portions (34) for fitting with end portions of the battery cells (C). The lead plates (36, 37) are electrically connected to the corresponding electrodes (P, N) of the battery cells (C).