Medion Sarasota 8640 Replacement Battery 14.8V 4400mAh Li-ion

LION Sarasota 8640 Series — 14.8V Li-ion Replacement Battery (442673400015)

This is a 14.8V 4400mAh (65.12Wh) lithium-ion battery for the Medion Sarasota 8640 notebook range. It fits the Sarasota 8640, 8640C, 8640D, and 8640DH, among others. The cell matches the original voltage rail and connector pinout so the laptop powers on without hardware modification.

• Sarasota 8640 series fit: All variants in this range share the same 14.8V four-cell architecture, connector housing, and BMS communication protocol — which is why one cell covers the 8640, 8640C, 8640D, and 8640DH without any adapter.
• Bench tested on actual hardware: We ran this cell through charge, full-load discharge, and reconnect cycles. The BMS negotiated correctly with the host system, charge current stepped down at the expected voltage threshold, and no overcurrent trip occurred at peak CPU and display draw.
• First cycle after install: After fitting this cell, run the laptop on battery until it hibernates on its own, then charge it uninterrupted to 100%. This forces the BIOS battery learn cycle to reset against the new cell's actual capacity and clears the false "poor health" warning that appears after any cell swap on this platform.

BIOS reporting battery health as poor immediately after replacement

The Medion Sarasota BIOS stores charge history and health data from the previous cell in its EEPROM. When a new cell goes in, the BIOS compares current readings against that stored profile and flags a mismatch as degraded health. This is not a fault with the replacement cell. Running one full discharge-to-hibernate followed by a full uninterrupted charge gives the BIOS enough data to rewrite its learned capacity baseline. After two or three complete cycles, the health indicator returns to normal.

Laptop shuts down at 20–30% charge shown on the gauge

This happens when the fuel gauge IC has not yet calibrated against the new cell's actual voltage curve. The gauge still maps against the old cell's degraded discharge profile, so the voltage cliff — where cell voltage drops sharply under load — arrives much earlier than the percentage shown. The fix is the same calibration cycle: discharge fully to hibernate cutoff, then charge to 100% without interruption. After two full cycles, the gauge IC recalibrates and shutdown aligns with the correct remaining capacity. If it persists past three cycles, check that the BIOS is not running a firmware-enforced charge limit below 14.0V cutoff.