About this replacement
Lenovo YOGA S940-14IWL / IdeaPad S940-14IWL — 7.72V Li-Polymer Replacement Battery (5B10T07386)
This is a 7.72V, 6550mAh (50.57Wh) lithium-polymer replacement battery for the Lenovo YOGA S940-14IWL and IdeaPad S940-14IWL ultrabooks. It matches OEM part numbers 5B10T07386, 5B10W67263, L18M4PC0, and SB10W67346. Voltage, connector pinout, and BMS communication protocol match the original cell exactly.
- S940 and IdeaPad S940 series compatibility: The YOGA S940-14IWL, IdeaPad S940-14IWL, and Yoga S940 81Q7 all share the same 7.72V voltage rail, identical connector, and the same BMS handshake protocol — one cell covers all three variants without modification.
- Bench tested on actual hardware: We ran this cell on an S940-14IWL unit and confirmed the BMS initialised correctly, BIOS accepted the battery as a known cell, and charging cycled cleanly through to 100% without an early cutoff flag.
- S940 battery learn cycle after install: After fitting this cell, run the laptop down until it hibernates, then charge uninterrupted to 100% without using the machine. This resets the BIOS battery learn cycle and clears the false "poor health" warning that appears after every cell swap on this platform.
BIOS reporting battery health as poor after replacement on the S940
The S940's embedded controller reads health data from the cell's EEPROM on first boot. A new cell carries factory-default EEPROM values that don't match the usage history the controller expects, so it flags health as degraded. This is a firmware interpretation issue, not a fault with the cell. Running one full discharge-to-hibernate followed by an uninterrupted charge to 100% allows the controller to write a fresh baseline and clear the warning. After two to three cycles the reported health figure stabilises.
S940 shutting down at 20–30% charge shown on screen
This happens when the fuel gauge IC hasn't yet calibrated against the new cell's actual chemistry. The IC carries forward voltage-to-capacity mapping from the old, degraded cell and misjudges the cutoff point. Under combined CPU and display load, voltage drops faster than the stale map predicts, and the system shuts down before the displayed percentage reaches zero. Run two full discharge-to-hibernate cycles and the fuel gauge IC recalibrates — shutdowns at false percentages stop once the map reflects the new cell's actual voltage curve at 7.72V nominal.