A surgical instrument comprising: an end effector comprising a moveable cutting instrument; a cutting instrument position sensor; a shaft connected at its distal end to the end effector; and a handle connected to a proximate end of the shaft, wherein the handle comprises: an electric motor for actuating the cutting instrument; and a motor control circuit for controlling the motor, wherein the motor control circuit comprises: a power source connected to the motor for electrically powering the motor; a charge accumulator device; and a switching circuit connected to the power source and the charge accumulator device for (i) temporarily connecting the charge accumulator device to the power source to charge the charge accumulator device, and (ii) selectively connecting the charge accumulator device in series with the power source to provide additional power to the motor, wherein the motor control circuit further comprises a current control circuit (144, 146), responsive to the cutting instrument position sensor and connected to the power source, for varying the current supplied to the motor from the power source such that the motor has at least: a first, low power operational mode for a first portion of a cutting stroke cycle of the cutting instrument determined by the cutting instrument position sensor; and a second, high power operational mode for a second portion of the cutting stroke cycle of the cutting instrument determined by the cutting instrument position sensor. an end effector comprising a moveable cutting instrument; a cutting instrument position sensor; a shaft connected at its distal end to the end effector; and a handle connected to a proximate end of the shaft, wherein the handle comprises: an electric motor for actuating the cutting instrument; and a motor control circuit for controlling the motor, an electric motor for actuating the cutting instrument; and a motor control circuit for controlling the motor, wherein the motor control circuit comprises: a power source connected to the motor for electrically powering the motor; a charge accumulator device; and a switching circuit connected to the power source and the charge accumulator device for (i) temporarily connecting the charge accumulator device to the power source to charge the charge accumulator device, and (ii) selectively connecting the charge accumulator device in series with the power source to provide additional power to the motor, wherein the motor control circuit further comprises a current control circuit (144, 146), responsive to the cutting instrument position sensor and connected to the power source, for varying the current supplied to the motor from the power source such that the motor has at least: a first, low power operational mode for a first portion of a cutting stroke cycle of the cutting instrument determined by the cutting instrument position sensor; and a second, high power operational mode for a second portion of the cutting stroke cycle of the cutting instrument determined by the cutting instrument position sensor. a power source connected to the motor for electrically powering the motor; a charge accumulator device; and a switching circuit connected to the power source and the charge accumulator device for (i) temporarily connecting the charge accumulator device to the power source to charge the charge accumulator device, and (ii) selectively connecting the charge accumulator device in series with the power source to provide additional power to the motor, wherein the motor control circuit further comprises a current control circuit (144, 146), responsive to the cutting instrument position sensor and connected to the power source, for varying the current supplied to the motor from the power source such that the motor has at least: a first, low power operational mode for a first portion of a cutting stroke cycle of the cutting instrument determined by the cutting instrument position sensor; and a second, high power operational mode for a second portion of the cutting stroke cycle of the cutting instrument determined by the cutting instrument position sensor.