Mitac MiNote 8640 Replacement Battery 14.8V 4400mAh

Mitac MiNote 8640 Series — 14.8V Li-ion Replacement Battery (442673400015)

This 14.8V, 4400mAh (65.12Wh) Li-ion battery pack replaces the original cell in the Mitac MiNote 8640, MiNote 8640D, and MiNote 8630 notebook computers. It matches the original connector, voltage rail, and BMS handshake required by the MiNote platform. Capacity figures come from the product specification, not third-party sources.

• MiNote 8630 / 8640 / 8640D platform fit: These models share a common 14.8V four-cell architecture and the same BMS communication protocol. That shared design means one cell works across the listed variants without modification to the connector or charge logic.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the MiNote platform. The BMS handshake completed on first connection, charge acceptance was normal, and the protection circuit responded correctly to both over-voltage and over-temperature triggers.
• Post-install calibration cycle on the MiNote: After fitting, run the laptop on battery until it hibernates at low cutoff, then charge uninterrupted to 100% without using the machine. This resets the BIOS battery learn cycle and clears the false "poor health" warning that appears after any cell swap on this platform.

BIOS reporting poor battery health immediately after fitting a new cell

The MiNote BIOS stores charge history and health data in an EEPROM register tied to the original cell. When a new cell arrives with no cycle history, the BIOS reads that blank state as degraded or unknown. This is not a fault with the replacement battery. Run one full discharge-to-hibernate cycle followed by an uninterrupted charge to 100% — this writes new baseline data to the learn cycle register and the health warning clears.

Laptop shuts down unexpectedly at 20–30% charge shown on screen

This happens when the fuel gauge IC has not yet calibrated against the new cell's actual discharge curve. Under combined CPU and display load, the cell voltage drops faster than the uncalibrated gauge predicts, and the system hits the low-voltage cutoff before the displayed percentage reaches zero. It is not a capacity fault. Run two to three full discharge-to-hibernate cycles — after that, the gauge IC builds an accurate voltage-to-capacity map and the premature shutdowns stop. Target resting voltage after a full charge should read 16.6–16.8V at the pack terminals.