Power tool, battery pack, and combination, and method of controlling the same

A power tool connectable to a battery pack, the battery pack including a first terminal, a first high current power supply terminal, a first low current power supply terminal, and a first control terminal, the power tool comprising:

• a second terminal electrically connectable to the first terminal of the battery pack;
• a second high current power supply terminal electrically connectable to the first high current power supply terminal of the battery pack;
• a second low current power supply terminal electrically connectable to the first low current power supply terminal of the battery pack;
• a second control terminal electrically connectable to the first control terminal of the battery pack;
• a motor, the operation of the motor being based on a high current provided through the second high current power supply terminal;
• a power circuit electrically connected to the second terminal and the second low current power supply terminal, the power circuit operable to provide a power based on a substantially continuous low current provided through the second low current power supply terminal;
• a user interface;
• a controller connected to the power circuit, the user interface, and the second control terminal, the controller operable to be powered by the power from the power circuit, and to provide a call for power to the battery pack over the second control terminal based on a signal received from the user interface.