Apple was able to fit in a larger battery with the 49mm case size. The Apple Watch Ultra is able to last for up to 36 hours on a single charge with normal use, and even longer with a new Low Power Mode.

"Normal" use for the 36 hour metric is 180 time checks, 180 notifications, 90 minutes of app use, and a 60-minute workout with music playing from the Apple Watch Ultra. It also includes a total of 28 hours of connection to the mobile device of your choice.

Depending on what the Apple Watch is used for, the actual battery life will be vastly different. It will drain the battery quicker if you work out for more than 60 minutes.

The Series 4 and later Apple Watches will be able to use the Low Power Mode in watchOS 9. The always-on display, autostarting workouts, and heart health notifications will be limited or disabled with Low Power Mode.

The Apple Watch Ultra has a feature that can be used to maximize the battery life, and this option will be available later in the year.

The Apple Watch Ultra will be the first Apple Watch to offer more than 24 hours of battery life and will last for 60 hours. Apple says that multi-day "adventure" battery life is based on Low Power Mode and with workout settings enabled for less heart rate and gps readings, which may be what battery maximization does. Apple tested the following.

  • 15 hours of workout
  • 600+ time checks
  • 35 minutes of app use
  • 3 minutes of talk time
  • 15 hours sleep tracking
  • 5 hours connected to ‌iPhone‌ via Bluetooth

The Apple watch can be extended to 36 hours with low power mode.

The Low Power Mode will launch with watchOS 9 on September 12th. Preorders for the Apple Watch Ultra are available today.