Fujitsu Amilo PI1505 10.8V Replacement Battery 805N00045

Fujitsu Amilo PI1505 Series — 10.8V Li-ion Replacement Battery (805N00045)

This is a 10.8V, 4400mAh Li-ion battery pack for the Fujitsu Amilo PI1505 and related mid-2000s Amilo notebooks. It replaces OEM part 805N00045 and cross-references 3S4000-G1S2-04, 3S4000-S1P3-04, and WP-UNL50/3. Fit models include the Amilo PI1506, PA150, and Li1820 among others.

• Amilo PI and PA platform coverage: The PI1505, PI1506, PA150, and Li1820 share the same 10.8V three-cell-series architecture and connector pinout. The BMS communication protocol and charge termination signal are identical across this group, so one cell format serves all of them without modification.
• Bench tested on actual hardware: We cycled this pack through charge termination and load discharge on the Amilo platform. The BMS communicated correctly with the system board, charge current tapered normally at full capacity, and no cell imbalance flags triggered during the test run.
• Post-install calibration on the Amilo: After fitting this cell, run one full discharge to hibernate-cutoff, then charge uninterrupted to 100%. The Amilo's BIOS battery learn cycle needs this reset to clear the inaccurate health warning that appears after every cell swap.

Amilo PI1505 shutting down at 20–30% shown on the gauge

This happens when the fuel gauge IC still holds calibration data from the old, degraded cell. The new cell has higher capacity, but the IC maps its voltage curve against the old baseline. Under combined CPU and display load, the system crosses a voltage threshold the IC reads as empty — even though charge remains. Run two full discharge-to-hibernate and charge-to-100% cycles. After the second cycle the IC recalibrates, and the cutoff point drops back to the correct low-voltage floor near 9.9V per pack.

BIOS reports 0% or "battery unknown" immediately after fitting new cell

The EEPROM in the old battery stored accumulated cycle data and rated Wh figures that the BIOS referenced on every boot. A new cell resets that data, so the BIOS briefly reads the pack as unrecognised or shows 0% until it completes a learn cycle. This is not a fault with the replacement cell. Boot with the charger connected, let the pack charge fully without interruption, then discharge to hibernate once. The BIOS will register the cell correctly and display accurate state-of-charge from that point forward.