A surgical circular stapler has a handle assembly, a shaft, a stapling assembly, and a firing assembly. The shaft extends distally from the handle assembly. The stapling assembly is secured to a distal end of the shaft. Longitudinal translation of the firing assembly causes the stapling assembly to drive a plurality of staples in a circular array to secure two lumens of tissue together. The stapling assembly may further drive a blade to sever any excess tissue interior of the circular array of staples. The stapler further includes an indicator configured to indicate "readiness" of the stapler and/or to control firing of the stapling assembly. The indicator may indicate a position of an anvil relative to the stapling assembly and/or coupling of the anvil to the stapling assembly among other things. In addition, the stapler may include a self-draining battery pack configured to drain power upon removal from the stapler.
