About this replacement
Samsung Gear S2 3G — 3.7V Li-Polymer Replacement Battery (EB-BR730ABE)
This is a 3.7V, 300mAh Li-Polymer cell that fits the Samsung Gear S2 3G smartwatch. It covers SM-R730, SM-R730A, and related variants sharing the EB-BR730ABE form factor. Capacity matches the original spec at 1.11Wh — no upsizing claims, no inflated figures.
- SM-R730 series fit: The SM-R730 and SM-R730A share the same battery bay dimensions, connector orientation, and BMS handshake. Swapping between these variants does not require any firmware change — the cell seats identically and the charge controller sees it as a valid source.
- Bench tested on actual hardware: We cycled this cell through the Gear S2 3G charge controller and confirmed the BMS accepted the cell without fault codes. Charge termination triggered cleanly at full voltage — no float-charge stall observed.
- Post-swap charge requirement: After fitting the new cell, place the watch on its magnetic charger immediately and charge to 100% before first use. The fuel gauge IC on the Gear S2 3G cannot calibrate its state-of-charge reference without a complete charge cycle from near-zero after a cell swap.
Why the Gear S2 3G charge controller rejects a new cell on first connect
When cell voltage drops below approximately 2.5V during storage or shipping, the Gear S2 3G BMS treats the cell as faulted and refuses to begin a standard charge cycle. The magnetic charger appears to sit idle — no vibration, no charge icon. Placing the watch on the charger for 10–15 minutes allows trickle pre-charge to bring the cell above the 2.8V threshold, after which normal CC/CV charging resumes automatically.
Watch showing 0% and refusing to boot after battery swap
This happens because the fuel gauge IC lost its reference voltage when the original cell was removed. The new cell is physically charged, but the IC has no stored baseline to map capacity against — it reads zero. Do not attempt repeated reboots. Place the watch on the charger and leave it connected until the display reports 100%. Once that full-charge reference point is written to the IC, the percentage readout will track accurately on subsequent cycles.