Samsung SPH-A680 Replacement Battery BEX239DSA 3.7V 1000mAh

Samsung SPH-A680 / VM-A680 — 3.7V Li-ion Replacement Battery (BEX239DSA)

This is a 3.7V, 1000mAh Li-ion cell built to the BEX239DSA specification for the Samsung SPH-A680 and VM-A680 flip phones. It slots into the original battery bay and connects to the phone's charge IC and fuel gauge circuit using the same pin layout as the factory cell. Voltage and capacity match the OEM spec exactly — 3.7V nominal, 3.7Wh.

• SPH-A680 and VM-A680 compatibility: Both models share the same battery bay dimensions, connector pinout, and charge IC. The BEX239DSA cell works across both variants because the voltage rail and BMS communication protocol are identical on each platform.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the SPH-A680 platform. The BMS accepted the cell without triggering protection cutoff, and the charge IC completed a full charge cycle to 4.2V without fault codes.
• Fuel gauge recalibration after installation: On first use, disable any fast-charge accessories and run one complete discharge-to-charge cycle. The phone's fuel gauge IC is calibrated to the old cell's discharge curve. One full cycle lets it re-anchor the coulomb counter to the new cell before drawing high current into an uncalibrated state.

Why the SPH-A680 reports wrong battery percentage after a cell swap

The SPH-A680 uses a fuel gauge IC that tracks charge state by mapping voltage curves from the previous cell over repeated cycles. When a new cell goes in, that stored curve no longer matches the actual discharge profile of the replacement. The gauge reads a voltage point and maps it to the wrong state-of-charge percentage. Running one full discharge down to auto-shutoff, then charging uninterrupted to 100%, forces the IC to rewrite its reference curve against the new cell.

Sudden shutdown at 20–30% remaining on the replacement cell

This happens when the fuel gauge IC still carries calibration data from a degraded original cell that had a steep voltage cliff near end-of-charge. The replacement cell hits a voltage point the gauge incorrectly reads as safe, but the phone's modem or backlight draws a current spike the gauge didn't anticipate — and the cell drops below the BMS undervoltage threshold instantly. The fix is the same full recalibration cycle: discharge to shutoff, charge to 4.2V without interruption. After one cycle, the gauge maps the new cell's flatter discharge curve and the premature shutoff stops.