About this replacement
Lenovo Flex 2 15 — 7.4V Li-ion Replacement Battery (L13M4A61)
This is a 7.4V, 4400mAh (32.56Wh) Li-ion replacement battery for the Lenovo Flex 2 15" convertible laptop. It fits the Flex 2 14 and Flex 2 15 series, including both the 14" and 15" screen variants. OEM part numbers covered include L13M4A61, L13S4A61, L13L4A61, L13L4E61, and 121500262.
- Flex 2 14 and 15 series compatibility: These models share the same 7.4V two-cell architecture, connector pinout, and BMS handshake protocol. One cell fits all variants in the Flex 2 range, from the standard 14 through to the 15" touchscreen 2-in-1 configuration.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on Flex 2 hardware. The BMS negotiated correctly with the Lenovo EC, accepted a full charge without tripping protection, and reported accurate state-of-charge data back to the OS fuel gauge within two cycles.
- Post-install calibration on Flex 2: After fitting, 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 Lenovo firmware.
BIOS reporting poor battery health after replacement on Flex 2
When you swap the cell in a Flex 2, the BIOS compares the new cell's EEPROM data against the stored charge history from the old battery. The mismatch triggers a false "poor health" or "replace battery" flag in Lenovo Vantage and the BIOS battery screen. This is not a fault with the new cell. Run one full discharge-to-hibernate cycle followed by an uninterrupted full charge — the BIOS learn cycle recalibrates against the new cell's actual capacity and clears the flag.
Flex 2 shutting down at 20–30% charge shown on screen
This happens when the cell voltage drops below the BMS cutoff threshold under combined CPU and display load, even though the OS fuel gauge still shows charge remaining. The fuel gauge IC reads state-of-charge from voltage curves calibrated to the old, degraded cell — so the reported percentage no longer reflects actual usable capacity. After fitting a new cell, the gauge needs two to three full discharge-and-charge cycles to re-map the voltage curve accurately. Once calibrated, the OS percentage and actual cell voltage will align, and the premature shutdowns stop.