About this replacement
Fujitsu LifeBook E448 / E449 Series — 14.4V Li-Polymer Replacement Battery (CP721834-01)
This 14.4V lithium-polymer battery replaces the original cell in the Fujitsu LifeBook E448 and E449 business notebook series. It carries a 3450mAh (49.68Wh) capacity and matches OEM part numbers CP721834-01, FMVNBP247, FPCBP531, and several closely related variants. The connector, BMS handshake, and cell dimensions match the original specification.
- LifeBook E448 / E449 platform fit: These models share a common battery bay geometry, 14.4V rail, and the same BMS communication protocol. A single cell design covers both generations without adapter or modification.
- Bench tested on actual hardware: We cycled this cell through charge, full-load discharge, and BMS handshake verification on the E-series platform. The protection circuit responded correctly to overvoltage and thermal thresholds, and BIOS recognised the cell without error flags after a learn cycle.
- Post-install calibration on the E-series BIOS: After fitting this cell, run one full discharge to hibernate cutoff, then charge uninterrupted to 100%. This resets the BIOS battery learn cycle and clears the inaccurate health or capacity warning that appears after every cell swap on this platform.
BIOS reporting battery health as poor immediately after fitting a new cell
The LifeBook E-series BIOS stores learned capacity data from the previous cell in its fuel gauge IC. When a new cell is installed, the old EEPROM data is still present, so the BIOS compares measured voltage against stale cycle history and flags the cell as degraded. This is not a fault with the replacement cell. Running a full discharge-to-hibernate followed by an uninterrupted charge to 100% forces the fuel gauge IC to relearn against the new cell's actual chemistry. After one or two full cycles, the health status clears and reported capacity aligns with the 49.68Wh rating.
Laptop shutting down at 20–30% charge shown on the status bar
This typically appears in the first few cycles after a battery swap, before the fuel gauge IC has calibrated against the new cell. The OS fuel gauge is still referencing voltage-to-capacity curves from the old, degraded cell, so it misreads the remaining charge. Under full CPU and display load, actual cell voltage drops faster than the gauge predicts, and the system hits the low-voltage cutoff while the indicator still reads 20–30%. Complete the post-install calibration cycle — discharge fully to hibernate, then charge to 100% without interruption. After two full cycles, the cutoff should align with a displayed level below 5%.