About this replacement
Asus ZenBook 14 UM425IA / ZenBook 13 UX325JA — 15.48V Li-Polymer Replacement Battery (C41N1904)
This is a 15.48V, 4250mAh (65.79Wh) Li-Polymer battery for the Asus ZenBook 14 UM425IA-R5DRDSB1, ZenBook 13 UX325JA series, X435EA, and over 157 additional ZenBook variants. The OEM part number is C41N1904, also cross-referenced as 02B200-03660500, 0B200-03660000, and C41N1904-1. If the original cell no longer holds charge under load, this is a direct cell-for-cell swap at the same voltage and form factor.
- ZenBook 14 UM425IA and UX325JA platform compatibility: These models share the same 15.48V four-cell architecture, identical connector pinout, and the same BMS handshake protocol — which is why a single part number covers both the UM425IA and UX325JA lines without modification.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on ZenBook-class hardware. The BMS negotiated correctly with the BIOS on first boot, reported the expected Wh figure in system info, and charge current tapered cleanly at full capacity without triggering any protection cutoff.
- Post-install calibration on ZenBook BIOS: After fitting this cell, run a full discharge until the laptop hibernates, then charge uninterrupted to 100% without interruption. This resets the BIOS battery learn cycle and clears the inaccurate health warning that typically appears after every cell swap on this platform.
Why ZenBook BIOS reports poor battery health immediately after a new cell swap
The ZenBook BIOS reads health data from an EEPROM register that carries over state-of-health figures from the old cell. A new cell physically installed does not automatically reset that register — the BIOS simply reads the last-known degraded value and flags it as poor. This is not a fault with the replacement cell. One full discharge-to-hibernate followed by an uninterrupted charge to 100% forces the fuel gauge IC to rewrite its baseline against the new cell's actual chemistry. After that cycle completes, the health warning clears and the reported capacity aligns with the rated 65.79Wh.
ZenBook shuts down at 20–30% remaining after battery swap
This happens when the fuel gauge IC has not yet calibrated against the new cell's discharge curve. Under combined CPU and display load, voltage drops faster than the old curve predicts — the BIOS hits its low-voltage cutoff while the gauge still shows 20–30% remaining. The cell is not faulty; the gauge is reading from a stale profile. Run two full discharge-to-hibernate cycles followed by uninterrupted charges to 100%, and the fuel gauge IC will rebuild an accurate curve against the new cell, eliminating the premature shutdown.