A:AnswerThere is no battery but I unplugged mine for a minute or so and when I plugged it in it retained the proper time. I wouldn’t rely on it if power failure is a concern.
If you bought this I assume you have a cell phone. Use the alarm in that! I’ve had my clock for 5 days and it has already gained 10 seconds! That’s one minute a month. At least it’s fast and not slow.