A battery assembly for use in a number of battery-powered, cordless ultrasonic surgical instruments with handles having a battery chamber and coupled to different ultrasonic waveguide types, comprises a housing having an exterior shape formed to removably connect with the battery chamber of the handles. The housing has at least one energy storage cell operable to power an ultrasonic-signal-generation assembly of the surgical instruments. The ultrasonic-signal-generation assembly is operable to dynamically produce a resonant wave along an ultrasonic waveguide. A battery/handle interface has a plurality of connectors shaped to mate with a plurality of corresponding connectors within the battery chamber of the handles. A voltage-control circuit communicatively couples with and provides power to the ultrasonic-signal-generation assembly, detects which one of the ultrasonic waveguide types is coupled to the handle connected to the housing, and provides an output in response to the detected waveguide type.