About this replacement
Samsung Gear 2 / SM-R380 / SM-R381 — 3.7V Li-Polymer Replacement Battery (PGF582224H)
This is a 3.7V, 250mAh Li-Polymer cell (0.93Wh) built to the same physical and electrical spec as the original Samsung Gear 2 battery. It fits the SM-R380, SM-R381, and Gear 2 Neo — all three share the same battery bay and connector. Use this when the original cell no longer holds a charge or the watch shuts down unexpectedly under load.
- SM-R380, SM-R381, and Gear 2 Neo compatibility: These three variants use the same 25.62 × 21.02 × 5.82mm cell footprint, identical connector pinout, and the same BMS handshake protocol. Swapping between them is not an issue — the fuel gauge IC reads the same cell chemistry on all three boards.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the SM-R380 platform. The BMS accepted the new cell without fault codes, and the fuel gauge updated state-of-charge correctly after a full charge cycle from near-zero.
- Fuel gauge reset after cell swap: After fitting this cell, place the watch on its magnetic charger immediately and charge to 100% before use. The fuel gauge IC on Gear 2 hardware cannot calibrate its reference point without a complete charge cycle from near-zero following a cell swap. Skipping this step causes the percentage to read incorrectly for days.
Why the Gear 2 drains faster with always-on display and continuous heart rate active
The Gear 2 heart rate sensor draws continuous current when monitoring is set to automatic — this is a known high-drain configuration for a 250mAh cell. Always-on display adds a steady backlight load on top of that. Together, these two settings can push total draw well above what the cell was sized for in standby-only use. If multi-day life is the goal, set heart rate monitoring to manual and let the display sleep — that alone significantly reduces average current draw on this cell size.
Watch not pairing to phone after battery replacement
Removing the battery during a swap kills the BLE session state stored in volatile memory — the watch loses its active pairing context. The phone-side Gear Manager or Galaxy Wearable app still shows the watch as paired, but the watch itself no longer holds a valid session key. Open the Galaxy Wearable app on the phone, remove the Gear 2 from the paired devices list, then re-pair from scratch using the watch's Bluetooth settings menu. The pairing completes within about 30 seconds once both sides are cleared.