Abstract: A DC power source unit supplies a DC voltage to a power tool through an adapter when a power switch of the tool is turned ON and also charges a battery pack used as an alternative power source of the tool when the power tool is not operated. In order to prevent a rush current from flow in a switch interposed between a switching power source circuit and the battery pack when charging the battery pack is commenced, the switch is rendered OFF when the output voltage from the switching power source is greater than the battery voltage. Charging the battery is started upon once lowering the output of the switching power source to a level lower than the battery voltage.

Abstract: A DC power source unit supplies a DC voltage to a power tool through an adapter when a power switch of the tool is turned ON and also charges a battery pack used as an alternative power source of the tool when the power tool is not operated. A minimum battery temperature gradient amongst battery temperature gradients ever computed is used to determine whether the battery pack has cooling effect when forcibly cooled by a cooling fan or whether the battery pack has reached a full charge condition. When charging the battery pack is interrupted due to operation of the power tool, computing the battery temperature gradient is halted for some time or determination of the battery pack's full charge condition is not performed for some time in order to prevent the minimum battery temperature from being updated during interruption of charging of the battery pack.

Abstract: A battery charger includes a battery voltage detector for detecting the voltage of a secondary battery and a battery temperature sensor for detecting the temperature of the secondary battery. A controller determines the voltage of the secondary battery prior to beginning the charging process based on output from the battery voltage detector. The controller also determines the charging level from among a plurality of levels that indicate how much time is required for the secondary battery to reach a full charge, based on the determined voltage of the secondary battery and output from the battery temperature sensor. A display is provided for displaying the charging level that indicates the time remaining to achieve a full charge.

Abstract: A charging apparatus includes a cooling fan; a battery temperature detecting unit; and a control unit configured to determine presence or non-presence of cooling effect by the cooling fan, and to control a charging current based on an output of the battery temperature detecting unit. When there is no cooling effect and the battery temperature reaches a first predetermined value smaller than a maximum value of a temperature range in which a battery is chargeable without making a life time thereof shorter, the control unit changes the charging current to a first charging current value where increase of the battery temperature can be suppressed. When there is cooling effect and the battery temperature reaches a second predetermined value higher than the first predetermined value, the control unit changes the charging current to a second charging current value larger than the first charging current value.