A surgical instrument, comprising: (a) a shaft assembly having a distal end portion and a proximal end portion, the distal end portion including an end effector projecting distally therefrom; (b) a handle assembly configured to receive the proximal end portion of the shaft assembly, wherein the handle assembly includes a battery dock; and (c) a battery unit configured to be received by the battery dock such that the battery unit is in electrical communication with at least one of the shaft assembly or the handle assembly, the battery unit including: (i) a battery, wherein the battery comprises: an anode contact, and a cathode contact, and (ii) a discharge drain including: a controller, and a battery power draining element, wherein the controller is configured to selectively place the battery power draining element in communication with the anode and cathode contacts to thereby drain power from the battery in response to coupling of the battery unit with the battery dock; wherein the controller includes a timer is configured to sense attachment of the battery unit to the battery dock and responsively begin tracking, wherein the timer is further configured to selectively place the battery power draining element in communication with the anode and cathode contacts to thereby drain power from the battery after a predetermined amount of time has elapsed since the attachment of the battery unit to the battery dock. (a) a shaft assembly having a distal end portion and a proximal end portion, the distal end portion including an end effector projecting distally therefrom; (b) a handle assembly configured to receive the proximal end portion of the shaft assembly, wherein the handle assembly includes a battery dock; and (c) a battery unit configured to be received by the battery dock such that the battery unit is in electrical communication with at least one of the shaft assembly or the handle assembly, the battery unit including: (i) a battery, wherein the battery comprises: an anode contact, and a cathode contact, and (ii) a discharge drain including: a controller, and a battery power draining element, wherein the controller is configured to selectively place the battery power draining element in communication with the anode and cathode contacts to thereby drain power from the battery in response to coupling of the battery unit with the battery dock; wherein the controller includes a timer is configured to sense attachment of the battery unit to the battery dock and responsively begin tracking, wherein the timer is further configured to selectively place the battery power draining element in communication with the anode and cathode contacts to thereby drain power from the battery after a predetermined amount of time has elapsed since the attachment of the battery unit to the battery dock. (i) a battery, wherein the battery comprises: an anode contact, and a cathode contact, and an anode contact, and a cathode contact, and (ii) a discharge drain including: a controller, and a battery power draining element, wherein the controller is configured to selectively place the battery power draining element in communication with the anode and cathode contacts to thereby drain power from the battery in response to coupling of the battery unit with the battery dock; wherein the controller includes a timer is configured to sense attachment of the battery unit to the battery dock and responsively begin tracking, wherein the timer is further configured to selectively place the battery power draining element in communication with the anode and cathode contacts to thereby drain power from the battery after a predetermined amount of time has elapsed since the attachment of the battery unit to the battery dock. a controller, and a battery power draining element, wherein the controller is configured to selectively place the battery power draining element in communication with the anode and cathode contacts to thereby drain power from the battery in response to coupling of the battery unit with the battery dock; wherein the controller includes a timer is configured to sense attachment of the battery unit to the battery dock and responsively begin tracking, wherein the timer is further configured to selectively place the battery power draining element in communication with the anode and cathode contacts to thereby drain power from the battery after a predetermined amount of time has elapsed since the attachment of the battery unit to the battery dock.