About this replacement
Fujitsu LifeBook E4512 / E5512 Series — 15.12V Li-Polymer Replacement Battery (CP801785)
This 15.12V, 4250mAh (64.26Wh) Li-Polymer battery replaces the original CP801785 / FMVNBP253 / FPB0360S / FPCBP592 cells across the Fujitsu LifeBook E4512, E5512, E5512A, and U7411 series. It slots into the same bay and connects to the same BMS handshake points as the factory unit. Voltage and connector type are matched to the original spec.
- LifeBook E4512 / E5512 / E5512A / U7411 compatibility: These models share the same 15.12V four-cell LiPo architecture, identical connector pinout, and the same BMS communication protocol — which is why one battery covers all of them. The fuel gauge IC talks to the BIOS over the same SMBus line regardless of which chassis you're working with.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the LifeBook platform and confirmed the BMS handshake completes correctly — the BIOS accepts the battery and initiates a normal charge sequence without throwing an unknown-device flag.
- Post-install calibration on the LifeBook E-series: After fitting this battery, run one full discharge down to hibernate cutoff, then charge uninterrupted to 100%. This gives the BIOS fuel gauge IC a full range reading against the new cell and clears the inaccurate health warning that appears after every cell swap on this platform.
Why the LifeBook E4512 shuts down at 20–30% after a battery swap
The LifeBook BIOS stores discharge curve data from the previous cell in its fuel gauge IC. When a new cell goes in, that stored curve no longer matches the actual voltage behaviour of the fresh chemistry. Under combined CPU and display load, the system reads the cell voltage against the old curve, hits what it thinks is the cutoff threshold, and triggers an emergency shutdown — even though usable capacity remains. Run a full discharge-to-hibernate then an uninterrupted charge cycle. After two to three full cycles, the fuel gauge re-learns the curve and the shutdowns stop.
BIOS reporting battery health as "poor" or "replace battery" immediately after fitting
This comes from stale EEPROM data carried over from the old battery — the BIOS compares the new cell's reported parameters against wear metrics logged from the previous unit and flags a mismatch as degradation. It is not a fault with the replacement cell. Run the Fujitsu battery utility (or access the BIOS battery learn cycle under Power settings) and initiate a full recalibration pass. After one complete discharge-to-cutoff and full recharge, the health indicator should clear and report correctly at 15.12V rated capacity.