Fujitsu LifeBook N3500 FPCBP94 Replacement Battery 10.8V

Fujitsu LifeBook N3500 Series — 10.8V Li-ion Replacement Battery (FPCBP94)

This 10.8V, 4400mAh (47.52Wh) Li-ion battery replaces the FPCBP94 and FPCBP94AP packs used in the Fujitsu LifeBook N3500 series notebooks. It fits the N3500, N3510, N3511, and N3520 — all share the same voltage rail and connector spec. Capacity figure is from the product data, not estimated.

• LifeBook N3500 series fit: The N3500, N3510, N3511, and N3520 run the same 10.8V battery platform with an identical connector pinout and BMS handshake protocol. One pack covers the full range without adapter or modification.
• Bench tested on actual hardware: We cycled this cell through charge, full-load discharge, and BMS cutoff on the N3500 platform. The BMS accepted the cell, reported charge status without fault codes, and cutoff fired at the correct low-voltage threshold.
• First-cycle calibration on the N3500: After installing, run one complete discharge until the laptop hibernates, then charge uninterrupted to 100% without interruption. This forces the LifeBook's BIOS battery learn cycle to reset against the new cell's actual capacity and clears the false "battery health poor" warning that appears after every cell swap.

BIOS reporting poor battery health immediately after swap on the LifeBook N3500

The LifeBook N3500 BIOS reads health data stored in the battery's EEPROM, not just live voltage. When a new cell arrives, that EEPROM data doesn't match the BIOS's learned baseline from the old pack, so it flags the replacement as degraded before a single cycle has run. This isn't a fault with the cell — it's a calibration mismatch. Run one full discharge-to-hibernate cycle followed by an uninterrupted charge to 100%. The BIOS learn cycle overwrites the stale EEPROM reference and the health warning clears.

LifeBook N3500 shutting down at 20–30% charge shown on the gauge

This happens when the fuel gauge IC still holds calibration data from the degraded original cell. The gauge reports 25% remaining, but the new cell's actual voltage curve doesn't match that old map — the laptop hits the undervoltage threshold before the gauge catches up. It's not a faulty replacement; it's a miscalibrated reference table. Run two to three full discharge-to-hibernate and full-recharge cycles to let the fuel gauge IC re-map against the new cell. After calibration, shutdown should not occur above 5–7% on a stable load.