Using an ultrasonic flaw detector, electrochemical-acoustic time of flight (EAToF) experiments are performed on commercially available alkaline Zn/MnO2 LR6 (AA) batteries during discharge. The EAToF data are compared to in situ energy-dispersive X-ray diffraction (EDXRD) data and scanning electron microscope (SEM) images taken post mortem. Changes in the acoustic waveforms from EAToF measurements are shown to correlate with dehydration of the Zn gel anode and formation of ZnO, as shown by peak evolution in the EDXRD data and morphology analysis using SEM. We show that the physical transitions during discharge change the transmission of an ultrasonic pulse, and that ultrasonic time-of-flight analysis can be used to determine differences between brands of alkaline AA cells. (C) 2016 The Electrochemical Society.