About this replacement
Asus Zenbook 14 UX433FQ / Zenbook Flip 13 UX362FA — 11.55V Li-Polymer Replacement Battery (C31N1831)
This is an 11.55V Li-Polymer replacement battery rated at 4150mAh (47.93Wh), built to the C31N1831 specification. It fits the Asus Zenbook 14 UX433FQ-A5105R, P574FA, Zenbook Flip 13 UX362FA-BP8505T, UX362FA-EL094T, and over 50 additional Asus ultrabook variants sharing the same connector and BMS handshake. It replaces the internal battery when the original cell has degraded or failed.
- UX433 and UX362 platform compatibility: Both series use the same 3-cell Li-Polymer configuration on the 11.55V rail, the same physical connector, and the same EEPROM-based BMS communication. That shared architecture is why one part number covers both chassis lines.
- Bench tested on actual hardware: We ran this cell on a UX433 chassis. The BMS handshake completed on first boot, charge negotiation initialized correctly, and the SMBus reported accurate cell voltage throughout the cycle. No trip events during charge or under CPU and display load.
- Post-installation learn cycle on Asus ultrabooks: After fitting this battery, discharge the laptop fully until it hibernates, then charge uninterrupted to 100% without interruption. This resets the BIOS battery learn cycle and clears the inaccurate health warning that appears in MyASUS or Windows after any cell swap.
BIOS reporting poor battery health immediately after fitting the C31N1831
The BIOS and MyASUS app read health data from EEPROM registers in the battery's BMS, not directly from cell voltage. When a new cell is installed, those registers haven't been written by a complete charge-discharge cycle on this chassis, so the system reports stale or null data as "poor health." Run one full discharge to hibernate cutoff, then a full uninterrupted charge to 100%. After that cycle, the BIOS rewrites the health registers against real measured data and the warning clears.
Laptop shuts down while battery gauge still shows 15–25% remaining
This is a voltage cliff, not a capacity fault. Under combined CPU turbo and display load, cell voltage drops faster than the fuel gauge IC can recalculate the state-of-charge curve. The BMS trips the output when voltage falls below the protection threshold — typically around 9.0V at the pack — even though the displayed percentage hasn't reached zero. The fuel gauge IC needs two to three full calibration cycles against the new cell before its discharge curve maps accurately. Run full discharge-to-hibernate then full charge cycles and the cutoff point will shift down to the correct low-percentage range.