About this replacement
Fujitsu LifeBook U727 / P727 Series — 10.8V Li-Polymer Replacement Battery (FPCBP530)
This is a 10.8V, 4150mAh (44.82Wh) Li-Polymer battery for the Fujitsu LifeBook U727, P727, P728, and U729. It replaces OEM part numbers FPCBP530, FPB0337S, FPCBP528, FMVNBP245, CP721833-01, CP734929-01, CP753148, and CP753148-01. The cell fits the original battery bay without modification and connects to the same BMS communication line.
- U727 / P727 / P728 / U729 platform fit: These models share a common battery connector, voltage rail, and BMS handshake protocol across the series. One cell covers all four, because Fujitsu standardised the battery interface across this ultrabook lineup.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the LifeBook platform. The BMS accepted the cell without a fault flag, reported state of charge correctly after calibration, and held voltage above the cutoff threshold under sustained CPU and display load.
- Post-install calibration on the LifeBook U727: After fitting this battery, run one full discharge to hibernate-cutoff, then charge uninterrupted to 100%. This resets the BIOS battery learn cycle and clears the inaccurate health warning that appears after every cell swap on this platform.
BIOS reporting poor battery health immediately after fitting a new cell
The LifeBook BIOS reads health data from EEPROM registers on the battery controller, not from live cell voltage. When a new cell goes in, those registers still hold degraded values from the old pack. The system flags the new battery as worn before it runs a single cycle. One full discharge-to-hibernate followed by an uninterrupted charge to 100% rewrites those registers with accurate data from the new cell. After that cycle completes, the BIOS health indicator will update and clear.
LifeBook U727 shutting down at 20–30% charge remaining
This happens when the fuel gauge IC has not yet calibrated against the new cell's actual discharge curve. The gauge is estimating remaining capacity based on the old cell's profile, so it loses accuracy as voltage drops under combined CPU and display load. The cell hits a voltage cliff the gauge did not predict, and the system shuts down. Run two full discharge cycles to hibernate-cutoff and charge each time to 100% — after the second cycle the fuel gauge IC recalibrates and the percentage readout stabilises above 10.8V under load.