About this replacement
Asus VivoBook 14 X403FA Series — 15.4V Li-Polymer Replacement Battery (C41N1825)
This is a 15.4V, 4600mAh (70.84Wh) Li-Polymer replacement battery for the Asus VivoBook 14 X403FA-EB123T and related VivoBook models. It slots into the same bay as the original C41N1825 cell and restores portable power to laptops that no longer hold a charge. OEM part numbers C41N1825 and 0B200-03250000 both apply to this fitment.
- VivoBook 14 X403FA and I403FA fitment: These models share the same 15.4V four-cell architecture, connector pinout, and BMS handshake protocol. The X403FA-EB123T, I403FA-2C, X403FA-EB011T, and VivoBook P3401FA-EB198R all draw from the same battery bay dimensions — 261.70 × 104.60 × 6.00mm — so one cell covers the full range.
- Bench tested on actual hardware: We ran this cell through charge-discharge cycles on the X403FA platform and confirmed the BMS negotiated correctly with the EC, accepted a full charge without tripping the over-voltage cutoff, and reported Wh capacity within expected tolerance in the OS.
- Post-install calibration on the X403FA: After fitting, run the laptop down to the hibernate-cutoff threshold — do not force-shut it off — 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.
BIOS reporting battery health as poor immediately after replacement
The X403FA's EC stores cycle count, health percentage, and design capacity in EEPROM on the original cell's protection board. When a new cell goes in, the BIOS reads stale EEPROM data and flags health as poor or unknown — the new chemistry hasn't been profiled yet. This isn't a fault with the replacement cell. Run one complete discharge-to-hibernate and a full uninterrupted charge to 100%; the BIOS learn cycle rewrites the health register against the new cell's actual voltage curve. After two or three calibration cycles, the health reading stabilises.
Laptop shutting down at 20–30% shown on the fuel gauge
This happens when the fuel gauge IC hasn't calibrated against the new cell's discharge curve yet. Under simultaneous CPU load and full display brightness, the cell voltage drops faster than the IC predicts, hitting the low-voltage cutoff before the displayed percentage reaches zero. The system reads it as a sudden shutdown, not a flat battery. Force a full discharge to hibernate, then charge to 100% without interruption — after two cycles, the fuel gauge IC maps the real voltage cliff and the shutdowns stop. If they persist past three cycles, check that BIOS battery charge optimisation is turned off in MyASUS or ASUS Battery Health Charging settings.