Lenovo F40 BATHGT31L6 Replacement Battery 11.1V 4400mAh

Lenovo F40 / F41 / F50 / V100 Series — 11.1V Li-ion Replacement Battery (BATHGT31L6)

This is an 11.1V, 4400mAh Li-ion battery for Lenovo F40, F41, F50, and V100 series notebooks. It replaces OEM part numbers BATHGT31L6, 43R1955, BATIGT30L6, 121TS040C, and 121TO010C. The battery fits the original connector and BMS communication protocol on all listed models.

• F40 / F41 / F50 / V100 platform fit: These models share the same 11.1V three-cell configuration, connector pinout, and SMBus BMS handshake, which is why one cell works across the entire range. The BIOS reads charge state and health data over the same bus on all variants.
• Bench tested on actual hardware: We cycled this cell on an F40 chassis under combined CPU and display load. The BMS held voltage above the 9.6V cutoff threshold through full discharge and accepted a clean charge curve from empty to 100% without interruption.
• First cycle after install: After fitting this cell, run the laptop down to hibernate-cutoff on battery alone, 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 false health warning that appears after every cell swap on these models.

BIOS reporting battery health as poor immediately after replacement

The F40 BIOS stores charge history and health data from the previous cell in its own memory — not just the battery's EEPROM. When a new cell goes in, that stored data does not match the new cell's readings, so the BIOS flags it as degraded. This is not a fault with the replacement cell. Running one full discharge-to-hibernate then a complete uninterrupted charge to 100% forces the learn cycle and overwrites the stale health data. After two or three of these cycles, the BIOS health indicator will reflect the actual condition of the new cell.

Laptop shuts down unexpectedly at 20–30% charge shown on screen

This is a voltage cliff problem. The fuel gauge IC in the battery was calibrated to the previous cell's discharge curve, and under full CPU plus display load the actual cell voltage drops below the BMS cutoff before the percentage shown on screen reaches zero. The OS fuel gauge has not yet mapped the new cell's real capacity. Run two full discharge-to-hibernate cycles, allowing the laptop to reach hibernate naturally each time, then charge fully to 100%. After these calibration cycles, the fuel gauge tracks the new cell correctly and the premature shutdowns stop.