The Fitbit One tracker is powered by a rechargeable built-in battery. To charge your Fitbit One, align the gold contacts on your tracker with the gold contacts on the inside of the charging cable, then plug it into your computer’s USB port or any other USB charging device. Charging typically takes about an hour and a full charge lasts about two weeks.
A battery indicator will appear when the Fitbit One is first plugged into the charging cable. You can hold down the tracker’s button while it is charging to see its current battery level.
You can also see your One tracker's battery level at the time of your last sync by clicking on the gear icon in the upper right corner of your Dashboard.
For tips on maximizing your tracker's battery life see Tracker battery information. For troubleshooting information, see My tracker's battery isn't charging.