About this replacement
Asus VivoBook S14 S432FL / S15 S532 Series — 11.55V Li-Polymer Replacement Battery (C31N1843)
This is a 11.55V, 3450mAh (39.85Wh) Li-Polymer replacement battery for the Asus VivoBook S14 S432FL-78AM5SB1 and VivoBook S15 S532 series ultrabooks. It matches the OEM part numbers C31N1843 and 0B200-03430000. The thin-cell form factor fits the 280.65 x 75.10 x 5.70mm battery bay used across the S432 and S532 chassis.
- S432 and S532 platform fit: Both series share the same three-cell Li-Polymer configuration, voltage rail, and BMS connector pinout — which is why one part number covers the full S432FL and S532FA/FL lineups. The BMS handshake protocol is identical across these chassis revisions.
- Bench tested on actual hardware: We cycled this cell on an S532FA unit and confirmed the BMS accepted the new cell without tripping an overcurrent fault. Charge termination occurred correctly at 12.6V and protection kicked in at the low-voltage threshold without a forced cutoff loop.
- Post-swap calibration on the S432/S532: After fitting this battery, run one full discharge down to hibernate cutoff, then charge uninterrupted to 100%. This resets the BIOS battery learn cycle and clears the false "poor health" warning the EC logs against every new cell it hasn't profiled yet.
Why the VivoBook S432/S532 shuts down at 20–30% after a battery swap
The embedded controller on these Asus ultrabooks maps shutdown thresholds against a stored discharge curve from the previous cell. When a new cell goes in, that curve no longer matches actual cell voltage behaviour, so the EC triggers a low-voltage shutdown well before the cell is genuinely empty. The fix is a full calibration cycle — discharge to hibernate, then a single uninterrupted charge to 100%. After two or three cycles, the fuel gauge IC re-learns the new cell's voltage slope and the premature shutdowns stop.
BIOS reporting 0% or "Unknown" capacity immediately after installation
The EEPROM on the old battery stored cycle count, design capacity, and health status data that the BIOS reads on boot. When a replacement cell arrives, that EEPROM data is either blank or factory-default, so the BIOS briefly reports 0% or flags the battery as unknown. This is not a fault with the replacement cell — it is the EC seeing an uncalibrated battery for the first time. Boot into Windows and let the battery charge to 100% without interruption; the EC will write its first health record to the new cell's EEPROM and the reading will normalise.