About this replacement
Asus UX360UA / Q324UA Series — 11.55V Li-Polymer Replacement Battery (C31N1538)
This 11.55V, 4800mAh (55.44Wh) Li-Polymer cell is a direct swap for the internal battery in the Asus UX360UA and Q324UA convertible ultrabooks. It replaces OEM part numbers C31N1538, 0B200-02080000, and C31Pq9H. When the original cell degrades and the laptop loses portability, this restores full off-charger operation.
- UX360UA and Q324UA platform fit: Both models share the same 11.55V three-cell architecture, slim 3.68mm cell profile, and connector pinout — which is why one SKU covers the full range including UX360UA-1A, UX360UA-1C, and 64 additional variants.
- Bench tested on actual hardware: We seated this cell in a UX360UA chassis, confirmed BMS handshake under Windows, and cycled charge through the full range. The protection circuit held cutoff correctly at both ends without tripping during normal display-plus-CPU load.
- Post-install calibration on the UX360UA: After fitting this cell, run one full discharge to hibernate cutoff, then charge uninterrupted to 100%. This resets the BIOS battery learn cycle and clears the inaccurate health or capacity warning that appears after every cell swap on this platform.
BIOS reporting poor battery health immediately after fitting a new cell
The UX360UA BIOS reads health data stored in the old cell's EEPROM and compares it against the new cell's reported values. When those don't match, it flags the battery as degraded before a single charge cycle runs. This is a firmware interpretation issue, not a fault with the replacement cell. Running one full discharge-to-hibernate then a complete charge cycle forces the BIOS to write fresh learn-cycle data and clear the warning.
Laptop shuts down at 20–30% shown on the fuel gauge
The fuel gauge IC on the UX360UA board calibrates its empty-point estimate against charge history from the previous cell. After a swap, it can map the wrong voltage as the cutoff floor, causing an early shutdown well before true depletion. Under combined CPU and display load, the new cell's voltage curve also drops faster than the IC expects during the first few cycles. Discharge fully to hibernate cutoff twice, letting the IC re-map the real voltage cliff — typically around 9.0V at the cell terminals under load.