The watch contains a rechargeable lithium battery. With normal use, a fully charged watch will run for approximately 7 days before needing a charge. When the battery level is at 15 percent, both the red and green LEDs will flash for 5 seconds to notify you that the battery needs to be charged. This will continue to happen every 5 minutes until the battery is drained completely or until you charge the watch.
IMPORTANT: Make sure that the watch syncs to the iFit app when the battery level is low; the data recorded on the watch will be deleted when the battery level is at zero percent.