Asus UX360CA Replacement Battery C31N1528 11.55V 4550mAh

Asus ZenBook Flip UX360CA — 11.55V Li-Polymer Replacement Battery (C31N1528)

This is an 11.55V, 4550mAh (52.55Wh) Li-Polymer battery for the Asus UX360CA 2-in-1 convertible ultrabook. It fits the ZenBook Flip UX360CA line, including the FC060T, C4215T, and C4050T variants among others. OEM part numbers C31N1528 and 0B200-00730200 both cross-reference to this cell.

• UX360CA series fit: All UX360CA models share the same 11.55V three-cell Li-Polymer architecture, the same flat-pack form factor at 309.00 × 135.20 × 4.50mm, and the same BMS handshake protocol. One cell covers the full variant list without modification.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the UX360CA platform. The BMS initialised correctly on first power-on, the charge controller accepted the cell without fault codes, and capacity reporting stabilised within two full cycles.
• First-cycle recalibration on the UX360CA: After fitting, run one full discharge down to hibernate cutoff, then charge uninterrupted to 100%. This resets the BIOS battery learn cycle and clears the inaccurate health warning the firmware throws after every cell swap.

Why the UX360CA BIOS flags a new cell as poor health immediately after swap

The UX360CA stores historical charge and discharge data in EEPROM on the original battery's BMS. When a new cell is installed, the BIOS reads no history and defaults to a poor-health or unknown status. This is a firmware read problem, not a fault with the replacement cell. Running the BIOS battery learn cycle — one full discharge to hibernate, one uninterrupted charge to 100% — populates the EEPROM registers and clears the warning. After two full cycles, the health indicator should read correctly.

UX360CA shutting down at 20–30% charge shown on screen

This happens when the fuel gauge IC has not yet calibrated against the new cell's actual voltage curve. The OS fuel gauge is reading a predicted state-of-charge based on the old cell's profile, so it displays 20–30% while the actual cell voltage has already hit the low-voltage cutoff. It is not a faulty cell — it is a mismatch between stored calibration data and the new cell's characteristics. Run two full discharge-to-hibernate and charge-to-100% cycles; after that, the fuel gauge re-maps its curve and the cutoff aligns with the displayed percentage.