About this replacement
Lenovo IdeaPad S340-15IIL — 11.34V Li-Polymer Replacement Battery (5B10T09095)
This 11.34V, 4400mAh (49.9Wh) Li-Polymer cell replaces the original battery in the Lenovo IdeaPad S340-15IIL (81WW) and a wide range of IdeaPad S340 and C340 variants. It matches the OEM voltage rail, connector pinout, and BMS communication protocol the IdeaPad S340 expects. Capacity figure is sourced from the physical cell — 4400mAh at 11.34V nominal.
- IdeaPad S340 and C340 series compatibility: These models share the same 11.34V three-cell Li-Polymer architecture, identical connector housing, and the same BMS handshake sequence over the SMBus line. A cell that works in the S340-15IIL will authenticate correctly in the S340-14IWL and C340-15IWL without modification.
- Bench tested on actual hardware: We seated this cell in an IdeaPad S340 chassis and cycled it through full charge and discharge under sustained CPU and display load. The BMS held charge termination at the correct cutoff voltage and passed authentication on every boot — no unknown device errors during testing.
- Post-installation calibration — IdeaPad S340 specific: After fitting, run the battery down until the laptop hibernates, then charge uninterrupted to 100% without interruption. This forces the BIOS battery learn cycle to reset against the new cell and clears the inaccurate health warning that appears after every cell swap on this platform.
BIOS reporting battery health as poor after IdeaPad S340 cell swap
When you replace the cell in an IdeaPad S340, the BIOS reads EEPROM data carried over from the old battery — cycle count, wear percentage, and capacity history. That stored data makes a fresh cell appear degraded. The fix is not a firmware update. Run the new cell through one full discharge-to-hibernate cycle followed by a full uninterrupted charge to 100%. After that cycle, the BIOS resets the learn counters and the health warning clears.
IdeaPad S340 shutting down at 20–30% charge shown on screen
This happens when the fuel gauge IC has not yet calibrated against the new cell's actual voltage curve. The IC is still using the old cell's discharge profile, so it misreads the remaining capacity and triggers a shutdown well before the cell is empty. It is not a faulty battery. Run two to three full discharge-and-charge cycles — by the third cycle, the fuel gauge IC has enough data to track the new cell accurately. After calibration, shutdowns at false low-percentage readings stop.