AMOI MD-1 Replacement Battery 3.7V 800mAh Li-ion

AMOI MD-1 — 3.7V Li-ion Replacement Battery (MD-1)

This is a 3.7V 800mAh Li-ion battery for the AMOI MD-1 mobile phone. It replaces the original cell when the factory battery no longer holds a charge or fails to power the device. Capacity is 800mAh (2.96Wh), matching the original specification.

• MD-1 platform fit: The MD-1 uses a single Li-ion cell at 3.7V nominal with a compact footprint measuring 51.76 × 37.98 × 4.34mm. This replacement matches that cell geometry and voltage rail so the device's charge IC sees the correct input parameters on startup.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on a controlled rig. The BMS held the cutoff voltage correctly at both ends — no premature termination at the top and no undervoltage lockout triggered during normal draw at the bottom.
• Fuel gauge recalibration on first cycle: On first use after installation, run the phone down to automatic shutdown, then charge it uninterrupted to 100% before use. The MD-1's fuel gauge IC is calibrated to the old cell's discharge curve — one full cycle resets that reference against the new cell.

Why the MD-1 reports wrong battery percentage after a cell swap

The MD-1 uses a fuel gauge IC that tracks charge state by comparing current draw against a stored discharge curve from the original cell. When a new cell goes in, that stored curve no longer matches actual cell behaviour, so the reported percentage drifts. This shows up most often as the phone displaying 40% and then shutting down without warning. One full discharge-to-shutdown followed by an uninterrupted charge to 100% forces the IC to re-map the curve against the new cell's actual capacity and internal resistance.

Sudden shutdown at 20–30% on the replacement cell

This happens when the cell voltage drops below the load threshold faster than the fuel gauge IC expects — a voltage cliff. Under screen-on or active-radio load, the cell cannot sustain voltage above the protection cutoff even though the reported percentage says it should have capacity remaining. The root cause is a mismatch between the IC's stored model and the new cell's actual voltage-versus-capacity curve. Complete the recalibration cycle first — discharge fully to auto-shutdown, then charge to 100% — and confirm the cell resting voltage reads 4.1–4.2V at full charge before normal use.