It sure does!! The Doppler has an internal, non-replaceable battery inside that charges whenever the Doppler is plugged in. If there is ever a power outage the battery backup will keep your time, and make sure your alarm goes off at the proper time using an internal buzzer. These backed up alarms can't be snoozed, but can be shut off using the alarm button. The battery backup will last around 12 hours. Finally on battery backup the screen, buttons, and  USB ports will not function.