About this replacement
Samsung Galaxy Watch 4 40mm / SM-R880 — 3.88V Li-Polymer Replacement Battery (EB-BR880ABE)
This 3.88V, 240mAh Li-Polymer cell replaces the original battery in the Samsung Galaxy Watch 4 40mm, SM-R880, SM-R880N, and SM-R885. It restores power to the watch's display, heart rate sensor, activity tracking, and notification functions. Capacity is 240mAh (0.93Wh), matching the original cell specification.
- SM-R880 / SM-R885 platform fit: These models share the same 3.88V cell format, connector pinout, and BMS communication protocol. The fuel gauge IC on all variants reads state-of-charge from the same register set, so this cell slots in without firmware conflict.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on the SM-R880 platform. The BMS accepted the new cell without triggering a protection cutoff, and the fuel gauge re-calibrated correctly after a full charge cycle from near-zero.
- Post-swap charge requirement: After fitting this cell, place the watch on its magnetic charger immediately and charge to 100% before use. The fuel gauge IC loses its state-of-charge reference during a cell swap and cannot set an accurate baseline without one full charge cycle from near-zero.
Why the SM-R880 fuel gauge reads incorrectly after a cell swap
The Galaxy Watch 4 uses a coulomb-counting fuel gauge IC that tracks charge by integrating current over time from a known reference point. When the original cell is removed, that reference is lost entirely. The IC does not automatically reset — it resumes counting from whatever value was stored in non-volatile memory. A full charge cycle from near-zero forces the IC to re-anchor its 100% and 0% endpoints against the new cell's actual capacity, correcting percentage readings across the full range.
Watch not pairing to the Galaxy app after battery replacement
Removing the battery during a swap terminates the active BLE session between the watch and the paired phone. The Galaxy Wearable app holds the previous session key and will not automatically re-establish a connection after power is restored. On the watch, go to Settings → General → Reset, then open the Galaxy Wearable app on the phone and select Add new device. Re-pairing takes under two minutes and restores all notification and health sync functions.