Samsung Galaxy S II EB-F1A2GBU Compatible Battery 3.7V 1300mAh

NTT DoCoMo Galaxy S II SC-02C — 3.7V Li-ion Replacement Battery (EB-F1A2GBU)

This is a 3.7V 1300mAh Li-ion battery for the NTT DoCoMo Galaxy S II SC-02C smartphone. It replaces OEM part numbers EB-F1A2GBU and EB-FLA2GBU. It fits the SC-02C variant sold through NTT DoCoMo's Japanese network.

• SC-02C platform fitment: The Galaxy S II SC-02C shares its battery bay dimensions and connector pinout with Samsung's original EB-F1A2GBU cell. The BMS communication lines match, so the phone's charge IC accepts the replacement without triggering an authentication error.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the SC-02C. The BMS held charge termination at 4.2V and activated low-voltage cutoff before the cell dropped below safe thresholds under full display and modem load.
• Fuel gauge recalibration on first use: After installing this cell, disable fast charging and run one full discharge-to-charge cycle before normal use. The SC-02C's fuel gauge IC holds its calibration curve from the old cell — one complete cycle lets the coulomb counter map the new cell's actual discharge profile accurately.

Why the SC-02C reports wrong battery percentage after a cell swap

The SC-02C uses a coulomb counter that builds its capacity model from the previous cell's charge and discharge history. When you swap in a fresh cell, that stored model no longer matches the new cell's voltage curve. The phone reads voltage and maps it against an outdated table, so the percentage shown on screen drifts from the real state of charge. One full discharge to automatic shutdown followed by an uninterrupted charge to 100% forces the fuel gauge IC to rebuild its calibration against the replacement cell.

Sudden shutdown at 20–30% on the replacement cell

This happens when the cell voltage drops sharply under high-draw loads — active LTE radio, bright display, or GPS running simultaneously. The SC-02C's BMS trips the cutoff when cell voltage sags below roughly 3.4V under load, even though the fuel gauge still shows charge remaining. The root cause is that a freshly installed cell has not yet had its internal resistance profiled by the phone's power management IC. Run one full calibration cycle and monitor whether shutdowns continue — if voltage at shutdown reads above 3.5V on a battery app, the fuel gauge IC is still recalibrating against the new cell curve.