Samsung Galaxy S SC-02B Compatible Battery 3.7V 1250mAh

NTT DoCoMo Galaxy S — 3.7V Li-ion Replacement Battery (SC-02B)

This is a 3.7V, 1250mAh Li-ion battery for the Samsung Galaxy S SC-02B, the NTT DoCoMo Japan variant. It replaces the original cell when the handset can no longer hold charge, shuts down unexpectedly, or fails to power on. Dimensions are 51.00 x 50.50 x 5.50mm — confirm these against the original cell before fitting.

• SC-02B DoCoMo variant: The SC-02B shares the Galaxy S hardware platform but carries DoCoMo-specific firmware. The battery connector pinout and BMS handshake are identical to the base Galaxy S cell, so this replacement communicates correctly with the charge IC without triggering protection flags.
• Bench tested on actual hardware: We cycled this cell through full charge and discharge on the SC-02B. The BMS accepted the cell without error, the charge IC reached termination voltage at 4.2V, and the protection circuit tripped correctly at low-cell voltage during discharge stress.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging for one complete discharge-charge cycle. This lets the fuel gauge IC recalibrate against the new cell's discharge curve before high-current charging pushes current into an uncalibrated cell.

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

The Galaxy S uses a coulomb counter-based fuel gauge IC that stores a discharge curve calibrated to the original cell. When a new cell goes in, that stored curve no longer matches the actual cell chemistry and impedance. The phone reads an interpolated position on the old curve, so the percentage shown can be 10–20% off in either direction. One full discharge to automatic shutdown followed by an uninterrupted charge to 100% forces the IC to rewrite the curve against the new cell.

Sudden shutdown at 20–30% remaining on the SC-02B

This is a voltage cliff failure. When the modem transmits or the screen peaks in brightness, current draw spikes and the cell voltage drops sharply. If the cell cannot sustain voltage above the BMS cutoff threshold under that load, the protection circuit trips and the phone cuts out — even though the fuel gauge still shows charge remaining. The fix is to run one full recalibration cycle as above. If shutdowns persist after two full cycles, measure resting cell voltage with a multimeter — a healthy cell at 30% sits above 3.65V.