The Soundbrenner Core's battery has 4+ days battery life in watch mode, or 3+ hours of metronome playback.
The settings for brightness ad color of the LEDs, vibration intensity and BPM all have an impact on battery life during metronome usage. 3 hours can be achieved with an average, reasonable setting.
The Soundbrenner Core has a rechargeable battery and it takes about 1.5 hours to fully charge.