Samsung SCH-X609 Replacement Battery 3.7V 1000mAh Li-ion

Samsung SCH-X609 — 3.7V Li-ion Replacement Battery

This is a 3.7V, 1000mAh Li-ion replacement battery for the Samsung SCH-X609 mobile phone. It fits directly into the SCH-X609 and restores power to a handset where the original cell has degraded or failed to hold charge. Voltage and capacity match the original spec.

• SCH-X609 cell compatibility: The SCH-X609 uses a standard single-cell Li-ion pack at 3.7V nominal. The connector and BMS handshake on this replacement match the charge IC the phone expects, so the device powers on and charges without requiring firmware intervention.
• Bench tested on actual hardware: We cycled this cell through full charge and discharge on the SCH-X609 platform. The BMS held cutoff correctly at both ends — no overcharge trip, no premature low-voltage lockout during the discharge curve.
• Fuel gauge recalibration on first use: On first installation, disable any fast-charge mode and run one complete discharge-to-charge cycle before normal use. This lets the phone's fuel gauge IC map its coulomb counter against the new cell's actual discharge curve before high-current charging begins on an uncalibrated cell.

Why the SCH-X609 reports wrong battery percentage after a cell swap

The phone's fuel gauge IC stores a learned discharge curve from the old cell. When a new cell goes in, the IC is still referencing that old curve, so the percentage readout drifts — often reading higher than actual or jumping erratically. The fix is one full uninterrupted discharge down to automatic shutdown, followed by a full charge to 100%. After that cycle, the coulomb counter resets its reference points against the new cell and the percentage display stabilises.

Sudden shutdown at 20–30% on the replacement cell

This happens when the display or radio load pulls enough current that the cell voltage drops sharply below the BMS cutoff threshold before the fuel gauge catches up. On a new cell that hasn't been calibrated yet, the gauge can report 25% remaining while actual cell voltage has already sagged to 3.4V or below under load. The phone shuts down to protect the cell — not because the battery is faulty. Run one full calibration cycle as described above, and the gauge will learn where the real voltage cliff sits on this cell's curve.