About this replacement
Lenovo Chromebook S345-14AST / 14e ChromeBook — 11.52V Li-Polymer Replacement Battery (L18L3PG2)
This is an 11.52V, 4900mAh (56.45Wh) Li-Polymer replacement battery for the Lenovo Chromebook S345-14AST, 14e ChromeBook, and 14w series. It fits the 81WX, 81MH, and 81MQ chassis variants. Swap it in when the original cell no longer holds charge or causes unexpected shutdowns.
- S345, 14e, and 14w shared platform: These models run the same 11.52V three-cell battery rail with an identical connector and BMS handshake protocol. One cell fits the full group — L18L3PG2, L18M3PG2, and the 5B10T/5B10W/SB10T OEM numbers all cross-reference to this unit.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on a S345-14AST unit. The BMS handshook correctly, charging stepped through CC/CV phases without fault, and the protection circuit triggered cleanly at the low-voltage cutoff threshold.
- Post-swap recalibration cycle: After fitting this cell, run the Chromebook down 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 this platform.
Laptop shutting down at 20–30% remaining after battery swap
The BIOS fuel gauge IC still holds the discharge curve from the old, degraded cell. When the new cell's actual voltage at 25% doesn't match the stored curve, the system reads it as critically low and triggers a shutdown. The fix is a full calibration cycle — run to hibernate cutoff, charge to 100% without interruption, and repeat once more. After two cycles the fuel gauge IC maps the new cell's voltage curve and the early cutoff stops.
BIOS reporting battery health as "poor" or "replace soon" after fitting a new cell
The health flag lives in EEPROM data the BIOS carries over from the previous cell — it does not reset automatically when you install a new battery. On Lenovo Chromebooks, running the battery learn cycle (full discharge to hibernate, full uninterrupted charge to 100%) prompts the firmware to re-evaluate and rewrite that health status. If the warning persists after two full cycles, open Chrome diagnostics at chrome://diagnostics and verify the reported Wh value is close to 56.45Wh — a large deviation there points to an EEPROM mismatch worth noting before assuming a faulty cell.