Apple Watch S5/SE 40mm Battery

Description

Battery Model: A2277
Type: Lithium-ion (Li-ion) rechargeable battery — standard for Apple Watch smartwatches.
Capacity: ~245 mAh (milliamp-hours), which is about 0.944 Wh (watt-hours) — a compact battery optimized for all-day wearable use.
Voltage: Approximately 3.85 V.
Compatibility: Designed for 40 mm Apple Watch Series 5 and Apple Watch SE models (both first-gen 2020 and compatible later SE generation).

📌 Apple states the Series 5 and SE (40 mm) use a built-in rechargeable Li-ion battery that delivers up to ~18 hours of use on a single charge in typical mixed usage scenarios.