Fujitsu Amilo Pro V3405 Replacement Battery 11.1V 6600mAh

Fujitsu Amilo Pro V3405 Series — 11.1V Li-ion Replacement Battery (BTP-BAK8)

This 11.1V, 6600mAh (73.26Wh) Li-ion battery replaces the original BTP-BAK8 cell in the Fujitsu Amilo Pro V3405 and related Amilo Pro V3505, V3525, and V8210 notebooks. It slots directly into the standard Amilo Pro battery bay with the same connector and BMS handshake the laptop expects. Capacity figures are taken from the product data — not estimated from third-party sources.

• Amilo Pro V3405 / V3505 / V3525 / V8210 platform fit: These models share the same 11.1V three-cell-series architecture, battery connector pinout, and BMS communication protocol. A single cell works across the range because the BIOS negotiates charge parameters through the same SMBus interface on each board.
• Bench tested on actual hardware: We cycled this cell through charge, full discharge to hibernate cutoff, and a second full charge. The BMS reported state-of-charge correctly by the second cycle and held charge termination at the expected 12.6V threshold without false cutoff.
• Post-install calibration for the Amilo Pro: After fitting this cell, run one full discharge until the laptop hibernates, then charge uninterrupted to 100% without interruption. This resets the BIOS battery-learn cycle and clears the inaccurate health warning the Amilo Pro BIOS posts after every cell swap.

BIOS reporting poor battery health immediately after fitting a new cell

The Amilo Pro BIOS reads health data from EEPROM registers inside the battery's fuel gauge IC. When a new cell arrives, those registers still hold factory default values — not values calibrated to actual use. The BIOS compares them against its stored reference and flags the cell as degraded before a single charge cycle has run. One full discharge-to-hibernate followed by an uninterrupted charge to 100% rewrites the learned capacity values and clears the warning. After two cycles, the BIOS health indicator should read normal.

Amilo Pro shutting down at 20–30% charge shown on screen

This happens when the fuel gauge IC's learned capacity curve no longer matches the actual voltage curve of the new cell. The OS sees 25% remaining, but the cell voltage has already dropped below the BMS cutoff threshold under full CPU and display load. The laptop cuts power before the displayed percentage reaches zero. Fix it by running two full discharge-to-hibernate cycles followed by full uninterrupted charges — this forces the fuel gauge IC to recalibrate its discharge curve against the new cell's actual chemistry. After calibration, shutdown should not occur above 5% indicated.