A surgical instrument comprises a surgical end effector having an actuation assembly operable to effect a surgical procedure when actuated, a part (60, 1060, 102) of the actuation assembly being movable between a first position and second position, and a handle (10) connected to the end effector for actuating the actuation assembly. The handle has a power supply (1500) disposed within the handle (10), a motor (1520) disposed within the handle (10) and electrically p*owered by the power supply (1500), a transmission connecting the motor (1520) to the movable part (60, 1060, 102) and operational to displace the movable part (60, 1060, 102) anywhere between the first and second positions when the motor (1520) is operated, and a manual release mechanism (1800) that selectively interrupts the transmission and, during interruption, displaces the movable part (60, 1060, 102) towards the first position independent of operation of the motor (1520).
