Abstract: In a battery charger of the type using a car battery as a power source for charging a rechargeable batter, when a low voltage state of the car battery continues for a first predetermined period of time, charging of the rechargeable battery will be interrupted. However, charging of the battery will be resumed when the voltage of the car battery reverts to a predetermined allowable voltage before expiration of a second predetermined period of time. If the low voltage state of the car battery continues for the second predetermined period of time, charging of the rechargeable battery is no longer performed.

Abstract: To enable recharging of a battery under a low temperature circumstance, a rapid battery charger is provided with a rapid charge mode and a slow charge mode which are selectively used depending upon the temperature of the battery. The rapid charge mode is selected when the temperature is above a predetermined value, wherein the battery charger charges the battery with a charging current of more than 5 C, whereas the slow charge mode is selected when the temperature is below the predetermined value, wherein the battery charger charges the battery with a charging current of less than 1 C.

Abstract: A control circuit for use in an electrically powered tool, such as a screw driver, includes a double-pole double-throw (DPDT) relay switch having two wiper contacts movable between ON and OFF positions. A motor is connected to a power supply through the DPDT relay switch. To stop the rotations of the motor, the two wiper contacts trip from ON positions to OFF positions in ganged fashion. With the use of DPDT relay switch, even if one of the two wiper contacts undergoes chattering actions at its OFF position, the remaining wiper contact allows a large braking current to flow in a closed loop, whereby contacts of the DPDT relay switch are prevented from being melted caused by the braking current.