In the present invention, a battery pack type discriminating or deciding concave portion (131) is formed at a position corresponding to a battery pack type deciding switch (214) of an SQ battery pack (1) and when the SQ battery pack (1) is set, the battery pack type deciding switch (214) is avoided to be pressed by a bottom (115) of the SQ battery pack (1) owing to the concave portion (131). In this way, as the switch (214) is avoided to be pressed, it is recognized that the set battery pack is an SQ battery pack (1) under charging. Therefore, according to the present invention, it is possible to identify battery packs among different charging modes and charging can be performed in a proper charging mode.