About this replacement
Lenovo IdeaPad S10-2 Series — 11.1V Li-ion Replacement Battery (L09C3B12)
This is an 11.1V 4400mAh (48.84Wh) Li-ion replacement battery for the Lenovo IdeaPad S10-2 netbook. It fits the S10-2, S10-2 20027, and S10-2 2957 variants. OEM part numbers covered include L09C3B12, L09C6Y12, L09M3B11, 55Y9382, 55Y9383, and several others listed in the compatibility table.
- S10-2 variant compatibility: The 20027 and 2957 sub-models share the same 11.1V three-cell architecture, connector pinout, and BMS handshake protocol — which is why a single cell covers all three board revisions without modification.
- Bench tested on actual hardware: We cycled this cell on the S10-2 platform and confirmed the BMS negotiates correctly at initial power-on, charge current ramps normally from the AC adapter, and the protection circuit trips at expected low-voltage cutoff without false disconnects.
- Post-install calibration on the S10-2: After fitting this cell, run one full discharge to hibernate cutoff, then charge uninterrupted to 100% without interruption. This resets the BIOS battery learn cycle and clears the inaccurate health warning that appears after every cell swap on this platform.
Why the IdeaPad S10-2 shuts down at 20–30% after a battery swap
The S10-2 BIOS tracks a discharge curve learned from the previous cell. After a swap, it applies the old curve to a new cell — and those curves don't match. Under combined CPU and display load, the new cell's voltage drops faster than the stored curve predicts, triggering a false low-voltage shutdown well above actual empty. Running two to three full discharge-to-recharge cycles overwrites the stored curve. Once calibrated, the BIOS reads the new cell accurately and shutdowns at 20–30% stop occurring.
BIOS reporting 0% or "unknown" battery immediately after installation
The IdeaPad S10-2 reads battery identity and state-of-charge from EEPROM data embedded in the battery pack. A freshly installed cell has no discharge history in that register, so the BIOS fuel gauge IC has no reference point and reports 0% or flags the battery as unknown. This is not a fault with the cell itself. Plug in the AC adapter, let the battery charge to 100% without interruption, then allow a full discharge to hibernate — after that first cycle the fuel gauge IC maps the new cell correctly and the percentage reading stabilises.