About this replacement
Asus Zenbook UX305LA Series — 11.31V Li-Polymer Replacement Battery (C31N1428)
This is a 11.31V, 4500mAh (50.9Wh) Li-Polymer battery for the Asus Zenbook UX305LA, UX305UA-FC002R, UX305LA-FB004T, UX305UA-FC058T, and over 65 additional UX305-series variants. It replaces OEM part numbers C31N1428, 0B200-01450000, and 0B200-01450100. Capacity figures are taken directly from product data — not estimated from third-party sources.
- UX305LA and UX305UA compatibility: Both the LA and UA sub-variants use the same 11.31V three-cell Li-Polymer architecture, identical connector pinout, and the same BMS handshake protocol. One battery cell covers the full UX305 range without modification.
- Bench tested on actual hardware: We ran this cell on a UX305LA unit and confirmed the BMS initialised correctly, charge acceptance began immediately from a depleted state, and no protection trips occurred during a full charge cycle to 100%.
- Post-install calibration on UX305LA: After fitting, discharge the laptop fully until it hibernates, then charge uninterrupted to 100% without interruption. This runs the BIOS battery learn cycle and clears the inaccurate health or capacity warning that appears after every cell swap on this model.
Why the UX305LA BIOS reports poor battery health after a fresh cell install
The UX305LA stores battery health data in EEPROM on the original cell. When a new cell goes in, the BIOS reads that EEPROM baseline and flags a mismatch — the cell is new but the stored reference data is old. This shows up as a "Battery health poor" or "Replace battery" alert even on a brand-new replacement. It is not a fault with the replacement cell. Running one full discharge-to-hibernate followed by an uninterrupted charge to 100% writes a fresh EEPROM reference and clears the warning.
UX305LA shutting down with 20–30% charge still showing on screen
This happens when the fuel gauge IC has not yet calibrated against the new cell chemistry. The IC is still using voltage-to-capacity curves from the degraded original cell, so it reads 25% when the actual cell voltage is already near cutoff. Under full CPU and display load, the voltage drops sharply below the BMS protection threshold and the laptop cuts power instantly. The fix is two to three full charge-discharge cycles — each one tightens the IC's curve mapping. After the third cycle, the percentage readout at shutdown should be below 5%.