About this replacement
Lenovo ThinkPad S5 Series — 14.8V Li-Polymer Replacement Battery (45N1166)
This 14.8V, 4250mAh (62.9Wh) lithium-polymer battery replaces the original cell in the Lenovo ThinkPad S5 and ThinkPad S5-0200 series notebooks. It cross-references OEM part numbers 45N1164, 45N1165, 45N1166, 45N1167, and PXD3X2. If your current battery no longer holds a charge or the system reports degraded health, this cell restores portable operation.
- ThinkPad S5 platform fit: The S5 and S5-0200 share a 14.8V four-cell rail with a standardised connector and BMS handshake protocol. This battery meets that voltage spec and communicates with the ThinkPad EC firmware without triggering an unrecognised-battery error on boot.
- Bench tested on actual hardware: We cycled this cell through full charge and discharge on a ThinkPad S5 unit. The BMS reported correct state-of-charge, charge current tapered normally at the top of the curve, and no thermal events occurred during the discharge phase.
- Post-install calibration on ThinkPad S5: 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 warning that appears after every cell swap on this platform.
BIOS reporting poor battery health immediately after installation
The ThinkPad BIOS reads health data stored in the old cell's EEPROM and compares it against the new cell's reported state. A fresh cell with no discharge history looks abnormal to the firmware because it has no cycle data yet. This is not a fault — it resolves after one full calibration cycle. Discharge the laptop fully until it hibernates, then charge to 100% without interruption, and the health indicator will update correctly.
Laptop shutting down at 20–30% battery remaining shown on screen
This happens when the fuel gauge IC has not yet calibrated against the new cell's actual voltage curve. The OS estimates remaining charge based on the old cell's curve, so the percentage shown does not match real cell voltage. Under full CPU and display load, the cell hits its lower voltage threshold before the gauge reaches 0%, and the system cuts power to protect itself. Run two to three full discharge-to-hibernate and full-charge cycles — the fuel gauge IC re-learns the curve and the shutdowns stop.