Binatone SM800 Replacement Battery 3.7V 800mAh

Binatone SM800 — 3.7V Li-ion Replacement Battery

This 3.7V, 800mAh Li-ion battery replaces the original cell in the Binatone SM800 feature phone. It fits directly into the SM800 battery bay and restores power to calls, messaging, and standard phone functions. Capacity is 800mAh (2.96Wh) as specified — no inflated figures.

• SM800 platform fit: The SM800 runs a low-voltage single-cell architecture at 3.7V nominal. This cell matches that voltage rail and the physical bay dimensions (50.00 × 38.00 × 4.80mm), so the connector seats correctly and the charge IC receives the expected cell impedance on first cycle.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the SM800 platform and confirmed the charge IC accepted the new cell without fault, BMS protection tripped correctly at low-voltage cutoff, and the fuel gauge began tracking state-of-charge within one full cycle.
• Fuel gauge recalibration after installation: On first use, run one complete discharge down to auto-shutoff, then charge to 100% without interruption. The SM800's fuel gauge IC is calibrated to the original cell's discharge curve — one full cycle against the new cell resets that reference and stops the percentage reading from jumping or stalling mid-charge.

Why the SM800 reports wrong battery percentage after a cell swap

The SM800 uses a fuel gauge IC that tracks capacity by measuring voltage and current against a stored discharge curve from the original cell. A new cell has different internal impedance and a slightly different voltage-to-capacity curve, so the gauge reads the wrong state immediately after installation. The phone may show 80% on a full charge or drop suddenly to 10% mid-use. One complete discharge-to-shutoff and uninterrupted full recharge forces the gauge to rebuild its reference curve against the new cell.

Sudden shutdown at 20–30% on the replacement cell

This happens when the cell voltage drops below the phone's minimum operating threshold under load — typically during a call or screen-on activity — even though the gauge still shows charge remaining. The fuel gauge IC has not yet mapped the new cell's voltage cliff, so it fails to warn the system before the cutoff hits. It is not a defective cell. Run two full discharge-charge cycles, and the gauge recalibrates its low-voltage prediction. After calibration, the phone will shut down correctly at or below 5% rather than at an inflated percentage.