About this replacement
Lenovo ThinkPad T440P / T540P / L440 / L540 — 11.1V Li-ion Replacement Battery (45N1144)
This is an 11.1V, 4400mAh (48.84Wh) Li-ion replacement battery for the Lenovo ThinkPad T440P, T540P, L440, and L540 series laptops. It matches the original cell count, voltage rail, and connector pinout. OEM part numbers covered include 45N1144, 45N1148, 45N1150, 45N1158, 45N1160, and over a dozen additional Lenovo part variants.
- T440P / T540P / L440 / L540 compatibility: These four ThinkPad lines share the same six-cell 11.1V battery bay, connector housing, and BMS communication protocol. A single cell fits all four without modification.
- Bench tested on actual hardware: We ran this cell on a ThinkPad T440P. The BMS handshake completed on first boot, the charge controller accepted the cell immediately, and the BIOS registered a valid battery status without requiring manual intervention.
- Post-install calibration cycle: 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 ThinkPad hardware.
BIOS reporting battery health as poor immediately after swap
ThinkPad firmware stores charge history and wear data in the old cell's EEPROM. When a new cell is fitted, the BIOS reads no accumulated cycle data and flags the battery as degraded or unknown. This is a firmware state issue, not a cell defect. Running one full discharge-to-hibernate then a full uninterrupted charge forces the BIOS to re-run its learn cycle against the new cell's actual capacity. After one or two complete cycles, the health status updates correctly.
Laptop shuts down at 20–30% charge shown on the gauge
This happens when the fuel gauge IC has not yet calibrated against the new cell's discharge curve. The old calibration data predicts a voltage floor that the new cell hits earlier under combined CPU and display load, triggering a hard cutoff before the displayed percentage reaches zero. It is not a faulty cell. Run two full discharge-to-hibernate cycles followed by full charges, and the gauge IC recalibrates its endpoint to match the new cell — shutdowns at false percentages stop after that.