About this replacement
Fujitsu LifeBook S6410 Series — 10.8V Li-ion Replacement Battery (FPCBP177)
This 10.8V 4400mAh Li-ion battery replaces the original FPCBP177 cell in the Fujitsu LifeBook S6410 and S6410C. It also fits the LifeBook S6421 and S6510 where OEM part numbers FPCBP179 and FPCBP179AP apply. Capacity is 47.52Wh at full charge.
- LifeBook S6410 / S6421 / S6510 compatibility: These models share the same 10.8V bus, identical connector pinout, and a common BMS handshake protocol. One cell covers the full range without modification.
- Bench tested on actual hardware: We cycled this cell on the S6410 platform and confirmed the BMS accepts the new cell without fault codes. Charge acceptance ran to 100% and the protection circuit tripped correctly at low-cell voltage during deep discharge testing.
- Post-install calibration on the S6410: After fitting, run the notebook down until it hibernates on its own, then charge uninterrupted to 100% without using the machine. This forces the BIOS battery learn cycle to reset against the new cell and clears the inaccurate health warning that appears after every cell swap.
BIOS reporting battery health as poor after fitting the new cell
The LifeBook BIOS stores capacity and cycle data in EEPROM on the battery pack itself. When you swap the cell, the BIOS reads stale data from the old charge history and flags the new pack as degraded. This is not a fault with the replacement cell. Run one full discharge-to-hibernate followed by an uninterrupted charge to 100% and the BIOS learn cycle will rewrite its baseline. After two or three full cycles the health indicator normalises.
S6410 shuts down at 20–30% remaining instead of hibernating at low battery
This symptom points to a voltage cliff in the cell, not the fuel gauge. Under combined CPU and display load the pack voltage drops sharply before the fuel gauge IC registers the correct state of charge. The BIOS hits the hardware undervoltage threshold and forces an immediate shutdown rather than a clean hibernate. To confirm, watch the reported voltage in a battery monitoring tool — if it drops below 10.0V under load while the percentage still reads above 20%, the calibration cycle above is needed. Run the full discharge-to-hibernate procedure and charge back to 100% without interruption to re-anchor the fuel gauge IC against actual cell voltage.