About this replacement
Asus VivoBook S13 S330 / X330 Series — 11.55V Li-Polymer Replacement Battery (C31N1806)
This is an 11.55V, 3600mAh (41.58Wh) Li-Polymer replacement battery for the Asus VivoBook S13 series, including the X330FA-3G, S330UA, and S330FA variants. It uses OEM part number C31N1806 and cross-references 0B200-02960000, 0B200-03030000, and 0B200-03030100. The three-cell flat-pack format matches the original cell footprint at 262.05 × 76.73 × 5.60mm.
- S330 and X330 platform compatibility: These models share the same battery bay dimensions, connector pinout, and BMS handshake protocol across the S330UA and S330FA sub-variants. The C31N1806 part number covers the full range because Asus used a common power rail at 11.55V across the series refresh.
- Bench tested on actual hardware: We ran this cell on an S330FA unit. The BMS initialised on first connection, the BIOS recognised the pack without prompting a health error, and charge current ramped correctly through CC/CV stages to full capacity.
- Post-install discharge cycle on the S330: After fitting, run one full discharge to hibernate cutoff, then charge uninterrupted to 100%. This resets the BIOS battery learn cycle on the S330 platform and clears the inaccurate health warning that appears after every cell swap on these Asus units.
Why the S330 BIOS reports poor battery health immediately after a cell swap
The Asus S330 stores charge-cycle data and health metrics in EEPROM on the battery pack itself, not in the laptop firmware. When a new cell is installed, the BIOS reads zero or mismatched EEPROM data and flags the battery as degraded or unknown. This is a data-state mismatch, not a fault with the replacement cell. Running one full discharge-to-hibernate then a complete uninterrupted charge lets the EC re-learn the new cell's capacity curve and clears the warning.
Laptop shuts down at 20–30% charge shown on the S330FA
This happens when the fuel gauge IC has not yet calibrated against the new cell's actual discharge curve. The IC is still mapping voltage drop against the old cell's profile, so it misreads the remaining capacity and triggers a low-battery shutdown well before the cell is empty. The fix is two to three full discharge-and-charge cycles without interruption. After calibration, the gauge tracks accurately and the laptop will reach the BIOS-set cutoff voltage — typically around 10.2V under load — before shutting down.