The Soundbrenner Core's battery lasts 3 days during daily usage.
When fully charged, it will last about 3 hours if you are continuously using the metronome.
The brightness of the LEDs, vibration intensity, selection of colours have an impact on battery duration. If you chose to use lower vibration intensities, less LED brightness, warmer colours or no no LED blinking at all; you can save battery from 20 minutes to up to 2 hours.
The Soundbrenner Core has a rechargeable battery and it takes about 1.5 hours to fully charge.