Samsung SPH-A310 Replacement Battery 3.7V 750mAh AB-A3108RA

Samsung SPH-A310 — 3.7V Li-ion Replacement Battery (AB-A3108RA)

This is the AB-A3108RA Li-ion cell for the Samsung SPH-A310 mobile phone. It runs at 3.7V with 750mAh (2.78Wh) capacity — matching the original specification. If the SPH-A310 no longer holds a charge or dies unexpectedly, this cell replaces the degraded original.

• SPH-A310 fitment: The AB-A3108RA uses the same physical footprint (60 x 45 x 6.80mm), connector pinout, and BMS handshake as the factory cell. The charge IC in the SPH-A310 communicates with the battery's protection circuit — a mismatch here stops charging entirely. This cell matches that protocol.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the bench, confirming the BMS protection circuit engages correctly at low-voltage cutoff and that the charge IC accepts the cell without throwing a fault state.
• Fuel gauge recalibration on first use: On first use after installation, disable any fast-charge mode and run one full discharge-to-charge cycle. The SPH-A310's fuel gauge IC was calibrated to the old cell's discharge curve — one complete cycle against the new cell resets that baseline before high-current charging is applied to an uncalibrated cell.

Why the SPH-A310 reports wrong battery percentage after a cell swap

The SPH-A310 uses a fuel gauge IC that tracks capacity by measuring voltage against a stored discharge curve from the original cell. When a new cell goes in, that stored curve no longer matches the actual cell chemistry — so the reported percentage drifts. The gauge may show 50% while the real state of charge is much lower, or it may jump several percentage points at once. One complete discharge down to auto-shutoff followed by a full charge corrects the calibration. After that cycle, percentage readings stabilise.

Sudden shutdown at 20–30% on the replacement cell

This happens when the cell voltage drops sharply under load — called a voltage cliff — before the fuel gauge reaches 0%. The SPH-A310's modem and display draw current in bursts; a new cell that hasn't been calibrated will hit the BMS low-voltage cutoff (around 3.0V per cell) while the gauge still reads significant charge remaining. The fix is completing the recalibration cycle described above. If shutdowns persist after two full cycles, check that the battery connector is fully seated — a loose pin increases resistance and accelerates voltage sag under load.