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All-day battery life is based on 18 hours with the following use: 90 time checks, 90 notifications, 45 minutes of app use, and a 30-minute workout with music playback from Apple Watch via Bluetooth, over the course of 18 hours.
Power Reserve notification (left), Charging the Apple Watch (middle and right). As for charge times, Apple says it takes about 1.5 hours to reach 80% and up to 2.5 hours for a full 100% charge. Real-world Watch battery performance.