About this replacement
Asus BX430 Series — 11.55V Li-Polymer Replacement Battery (C31N1620)
This is an 11.55V, 4200mAh (48.51Wh) Li-Polymer battery for the Asus VivoBook 14 BX430, BX430UA, BX430UQ, and EXPERTBook P5 P5340UA, among others. It replaces OEM part numbers C31N1620, C31POJ1, 0B200-02370000, and related variants. The cell format and connector match the original bay spec — no modification needed.
- BX430 platform compatibility: The BX430UA and BX430UQ share the same 11.55V three-cell architecture and the C31N1620 BMS handshake. The BIOS expects a specific voltage profile during charge negotiation — this cell meets that profile without triggering an unknown-battery error on boot.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on BX430UA hardware. The BMS accepted the cell, charge negotiation completed normally, and the fuel gauge IC registered capacity without manual intervention.
- Post-install calibration tip: After fitting this battery, discharge the laptop fully until it hibernates, then charge uninterrupted to 100% without waking the system. This gives the fuel gauge IC a complete reference cycle against the new cell and clears the inaccurate health warning that often appears after a cell swap.
Why the BX430 shuts down at 20–30% after a battery swap
The BX430's fuel gauge IC builds its discharge model from the old cell's EEPROM data. When a new cell is installed, the IC applies the old voltage-to-capacity curve to the new chemistry. The new cell's actual voltage cliff — where voltage drops sharply under CPU and display load — sits at a different point than the stored model expects. The system interprets that voltage drop as a near-empty state and triggers shutdown. Running one full discharge-to-hibernate cycle followed by an uninterrupted charge to 100% resets the reference data and corrects the cutoff behaviour.
BIOS reporting battery health as poor immediately after fitting a new cell
The BIOS on BX430-series units reads health status from EEPROM data written during the original cell's life cycle. A new cell arrives with fresh EEPROM counters that don't match the expected wear profile the BIOS was tracking. This mismatch causes Windows and the BIOS battery screen to flag the battery as degraded or unknown — even though the cell is new. The fix is to complete a full battery learn cycle: discharge to hibernate cutoff, then charge to 100% in one uninterrupted session. After one or two cycles, the BIOS recalibrates and the health warning clears.