Patent ID: 8210273

Claim:
An electric power tool comprising: a tool body; and a battery pack, the tool body including: a body side terminal that transfers an electric signal between the tool body and the battery pack; a drive portion that is electrically connected with the battery pack and supplied with electric power from the battery pack to be driven; a switch that is operable from outside of the tool body and issues one of a command to drive the drive portion and a command to stop the drive portion in accordance with operation to the switch; a terminal voltage setting unit that sets a voltage of the body side terminal to a first voltage when the command to drive the drive portion is issued by the switch; and a connection control unit that electrically disconnects the battery pack and the drive portion from each other when the voltage of the body side terminal is set to the first voltage and that electrically connects the battery pack and the drive portion with each other when the voltage of the body side terminal is set to a second voltage different from the first voltage, and the battery pack including: a battery side terminal that is electrically connected with the body side terminal of the tool body; a command recognition unit that generates a command recognition signal indicating that the command to drive the drive portion is issued by the switch of the tool body when a voltage of the battery side terminal is set to the first voltage; a permission determination unit that determines whether or not supply of electric power from the battery pack to the drive portion should be permitted, in accordance with a predetermined determination procedure including at least determination of a status of the command recognition signal; and a voltage changing unit that changes the voltage of the battery side terminal from the first voltage to the second voltage when supply of electric power from the battery pack to the drive portion is permitted by the permission determination unit.