Samsung SCH-A850 Replacement Battery BEX466DSAB 3.7V 850mAh

Samsung SCH-A850 — 3.7V Li-ion Replacement Battery (BEX466DSAB)

This is a 3.7V 850mAh Li-ion replacement for the Samsung SCH-A850 flip phone. It slots directly into the original battery bay and powers calling, messaging, and all basic device functions. Voltage and capacity match the OEM spec: 3.7V, 850mAh (3.15Wh).

• SCH-A850 fitment: The A850 uses a compact single-cell Li-ion pack with a low-current BMS suited to the phone's modest processor and GSM radio draw. This replacement matches that cell configuration and connector pinout exactly, so the device powers on and charges without triggering the protection circuit on first boot.
• Bench tested on actual hardware: We cycled this battery through full charge and discharge on the SCH-A850 platform. The BMS held charge cutoff at 4.2V and discharged cleanly down to the low-voltage lockout threshold without erratic shutdowns or protection trips during GSM voice calls.
• Fuel gauge recalibration on first use: After fitting this cell, run one full discharge down to automatic shutdown, then charge uninterrupted to 100% before normal use. The A850's fuel gauge IC was calibrated to the old cell's discharge curve — one complete cycle corrects the register and stops the percentage counter drifting.

Why the SCH-A850 reports wrong battery percentage after a cell swap

The A850's fuel gauge IC stores a learned discharge curve from the original cell. When a new cell goes in, the IC is still reading against that old curve, so the percentage shown on screen is out of sync with actual charge state. This causes the phone to show 40% and then shut down moments later — the display figure is simply wrong, not the battery. One full discharge-to-shutdown followed by a complete uninterrupted charge resets the coulomb counter and aligns the IC to the new cell's actual capacity.

Sudden shutdown at 20–25% on the replacement cell

This happens when the cell voltage drops below the GSM radio's minimum operating floor under transmit load — typically around 3.4V — even though the percentage display suggests charge remains. The fuel gauge hasn't yet mapped the new cell's voltage-to-capacity curve accurately, so it reports leftover percentage at a point where the cell can no longer sustain the current spike from a call or data burst. It is a calibration issue, not a faulty cell. Run one full discharge cycle without interruption and the shutdowns stop once the IC recalibrates its low-voltage threshold to the new cell.