Asus ZenBook Pro 14 UX480 C31N1803 Replacement Battery 11.55V

Asus ZenBook Pro 14 UX480 — 11.55V Li-Polymer Replacement Battery (C31N1803)

This is an 11.55V, 4400mAh (50.82Wh) lithium-polymer battery for the Asus ZenBook Pro 14 UX480, UX480FD, and UX450FD. It replaces OEM part numbers C31N1803 and 0B200-02980200. Physical dimensions are 196.00 × 113.50 × 7.50mm — confirm these against your existing cell before fitting.

• UX480 and UX450FD compatibility: Both the UX480FD and UX450FD run the same 3-cell 11.55V architecture with identical connector pinout and BMS communication protocol. One cell covers both models without any hardware modification.
• Bench tested on actual hardware: We ran this cell through charge, discharge, and charge-limit cycles on the UX480 platform. The BMS handshake completed correctly, charge control responded normally, and no overcurrent trips occurred during the test sequence.
• First-cycle recalibration on the UX480: After fitting, discharge the laptop to hibernate cutoff under normal load — do not force shutdown — then charge uninterrupted to 100%. This forces the fuel gauge IC to recalibrate against the new cell's actual capacity and clears the inaccurate health warning that appears in MyASUS and Windows Battery Report after every cell swap.

Why the UX480 shuts down at 20–30% shown after a battery swap

The UX480 uses a fuel gauge IC that stores a learned discharge curve from the previous cell in EEPROM. When a new cell is fitted, that stored curve no longer matches the actual voltage profile of the replacement. Under combined CPU and display load, the system hits a real voltage floor well before the gauge reaches 0%, triggering an emergency shutdown. The fix is a full discharge-to-hibernate cycle followed by an uninterrupted charge to 100% — this overwrites the old curve data. After two to three full cycles, the gauge reading and actual cutoff voltage will align.

BIOS showing battery health as "poor" or capacity as 0% immediately after fitting

This happens because the BIOS reads rated Wh from EEPROM data embedded in the battery controller, and the value written there may differ slightly from the outgoing cell's learned figures. The health algorithm flags this mismatch as degradation before any real-world cycling has occurred. It is not a fault with the replacement cell. Run the ASUS Battery Health Charging utility, set the mode to Full Capacity, complete one full discharge-to-hibernate and charge-to-100% cycle, then recheck — the health status will update once the BIOS completes its learn cycle.