About this replacement
Lenovo ThinkPad S3 — 15.56V Li-Polymer Replacement Battery (5B11K39157)
This is a 15.56V, 6400mAh (99.58Wh) Li-Polymer battery for the Lenovo ThinkPad S3 series, including model 83AG003QAU and over 200 compatible variants. It replaces the original cell when the system no longer holds charge or powers on from battery alone. OEM part numbers covered include 5B11K39157, L22B4PC3, L22M4PC3, and fifteen additional cross-references.
- ThinkPad S3 series compatibility: These models share the same 15.56V four-cell Li-Polymer architecture, connector pinout, and BMS handshake protocol. The SMBus communication between battery and EC firmware is identical across the 83AG range, so a single cell covers the full cluster.
- Bench tested on actual hardware: We cycled this cell through charge, full-load discharge, and hibernate-cutoff on a ThinkPad S3 unit. The BMS negotiated correctly with the EC at first boot, and the protection circuit tripped at the expected low-voltage threshold without triggering a false shutdown.
- First-cycle reset after installation: After fitting this cell, run one full discharge to hibernate-cutoff, then charge uninterrupted to 100%. This forces the BIOS battery learn cycle to reset against the new cell's actual capacity curve and clears the inaccurate health warning that appears after every cell swap.
BIOS reporting battery health as poor immediately after replacement
The ThinkPad EC reads health data from the battery's EEPROM, which stores cycle count, rated capacity, and degradation flags from the previous cell. When a new cell is installed, the EEPROM values don't automatically reset — so the BIOS inherits the old cell's wear history and displays a poor health warning even though the cell is new. Running the battery learn cycle (full discharge to hibernate, full uninterrupted charge) prompts the EC to re-baseline against the new cell. After one or two completed cycles, the health indicator updates to reflect the actual cell condition.
Laptop shutting down at 20–30% charge shown on screen
This is a voltage-cliff failure, not a fuel gauge error. Under combined CPU and display load, cell voltage drops faster than the fuel gauge IC can track — the pack hits the BMS low-voltage cutoff while the OS still reads 20–30% remaining. It happens most often when the calibration cycle has never been completed after fitting a new cell. Run a full discharge-to-hibernate followed by a complete charge to 100%, which forces the fuel gauge IC to recalibrate its state-of-charge model against the new cell's actual voltage curve. After calibration, the shutdown threshold and displayed percentage should align at or below 5%.