About this replacement
Lenovo IdeaPad S9 / S10 Series — 11.1V Li-ion Replacement Battery (L08C3B21)
This 11.1V, 5200mAh Li-ion battery replaces the original cell in the Lenovo IdeaPad S9, S9e, S10, and S10e netbooks. It cross-references OEM part numbers including L08C3B21, L08S3B21, ASM 42T4590, FRU 42T4589, and 45K127, among others. Rated at 57.72Wh, it matches the voltage and form factor of the factory-installed pack.
- IdeaPad S9 / S10 platform fit: The S9, S9e, S10, and S10e share the same battery bay geometry, connector pinout, and 11.1V BMS handshake. One cell specification covers the whole netbook series, which is why the OEM part number list is long — Lenovo sourced from multiple suppliers across production runs without changing the electrical spec.
- Bench tested on actual hardware: We cycled this pack on an IdeaPad S10e and confirmed the BMS communicated charge state correctly through the SMBus interface. Charge acceptance ran to the full rated capacity without the controller tripping a premature cutoff.
- First-cycle calibration on the IdeaPad S-series: After installing, run one full discharge down to hibernate cutoff, then charge uninterrupted to 100%. This resets the BIOS battery learn cycle and clears the inaccurate health warning that appears on the first boot after any cell swap.
BIOS reporting battery health as poor immediately after replacement
The IdeaPad S-series BIOS reads health data stored in the battery pack's EEPROM. A new cell ships with factory EEPROM values that don't match the discharge history the BIOS expects to see, so it flags the pack as degraded even though the cell is fresh. This is a data mismatch, not a hardware fault. Running the full discharge-to-hibernate then uninterrupted charge cycle forces the BIOS to rewrite its learned capacity baseline against the new cell. After one complete cycle, the health warning clears.
IdeaPad S10 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 voltage curve. The old calibration data predicts the voltage floor based on the worn cell — the new cell hits that predicted floor while still carrying usable charge, so the OS calls a shutdown early. The fix is completing two to three full discharge-charge cycles so the fuel gauge IC can map the new cell's real voltage-to-capacity relationship. After calibration, the gauge should track accurately and the cutoff should shift back to below 5% remaining.