About this replacement
Lenovo Legion Y740S / Y9000X — 15.36V Li-Polymer Replacement Battery (L19M4PG0)
This is a 15.36V, 3900mAh (59.9Wh) Li-Polymer battery for the Lenovo Legion Y740S, Legion Y740S-15IMH, and Legion Y9000X gaming notebooks. It replaces OEM part numbers L19M4PG0, L19C4PG0, SB10V26975, SB10V26972, 5B10V26973, 5B10W67240, 5B10W67169, and SB10W67233. The slim 4.54mm cell profile is specific to the Y740S and Y9000X chassis.
- Y740S and Y9000X fitment: Both models share the same internal battery bay dimensions, connector pinout, and BMS handshake protocol — which is why they draw from the same OEM part range. The 15.36V four-cell configuration matches the voltage rail these boards expect. Fitting a mismatched voltage cell will cause the BIOS to reject the pack entirely.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a Legion Y740S unit. The BMS communicated correctly over the SMBus interface, the BIOS recognised the pack without error, and the fuel gauge initialised from the first boot.
- Post-install calibration on Lenovo gaming notebooks: After fitting, run a full discharge to hibernate cutoff then charge uninterrupted to 100%. This forces the BIOS battery learn cycle to reset against the new cell data and clears the inaccurate health warning that appears after every cell swap on Lenovo Legion firmware.
BIOS reporting poor battery health immediately after fitting a new cell
The Legion BIOS reads health data from the battery's EEPROM on first contact. When a new cell arrives, that EEPROM holds default factory values that the firmware interprets as degraded capacity relative to rated spec. This is not a fault with the cell — it is a mismatch between stored EEPROM data and the BIOS learn cycle baseline. Run one full discharge to hibernate cutoff, then charge uninterrupted to 100%, and the firmware recalculates health against the actual cell. After that cycle the health indicator should read above 95%.
Laptop shuts down hard at 20–30% charge shown on screen
This happens when the fuel gauge IC has not yet calibrated against the new cell's voltage curve. The gauge maps a percentage to a voltage reading — if that mapping is still set to the old cell's curve, the percentage shown at shutdown can be well above zero. Under full CPU and display load, the cell voltage drops faster than the uncalibrated gauge expects, and the BMS triggers an emergency cutoff before the displayed percentage reaches the threshold. Complete two or three full charge and discharge cycles to let the gauge IC re-map the curve. After calibration, the cutoff will align with the actual cell voltage floor near 12.0V.