About this replacement
Asus Z450LA / Z450UA / Z550MA Series — 7.6V Li-Polymer Replacement Battery (C21N1434)
This is a 7.6V, 4900mAh (37.24Wh) Li-Polymer battery for the Asus VivoBook 14 and related Z-series notebooks. It fits the Z450LA-WX006T, Z450UA, Z550MA-1A, Z450UA-WX006T, and over 30 additional models sharing the C21N1434 platform. OEM part numbers covered include C21N1434, 0B200-01540000, and 0B200-01540100.
- Z450 / Z550 platform compatibility: These models share the same two-cell Li-Polymer pack format, 7.6V voltage rail, and EC connector pinout. The BMS handshake uses the same EEPROM protocol across the Z450LA, Z450UA, and Z550MA, so one cell fits all without adapter modifications.
- Bench tested on actual hardware: We ran this cell on a Z450LA unit and monitored charge cycles end-to-end. The BMS accepted full CC/CV charging without cutoff errors, and Windows reported charge state correctly by the second cycle.
- Post-install calibration on Z-series notebooks: After fitting this cell, run the laptop down to hibernate cutoff on battery power alone, then charge uninterrupted to 100%. This resets the BIOS battery learn cycle and clears the inaccurate health warning that appears after every cell swap on this platform.
Why the Z450LA BIOS flags a new battery as poor health immediately after swap
The Z450 EC reads battery health from EEPROM data embedded in the original cell — not from live voltage measurements. When a new cell goes in, the EEPROM counters reset to zero or read as mismatched, which the firmware interprets as a degraded pack. This is a data state problem, not a physical fault. Running one full discharge-to-hibernate followed by a complete uninterrupted charge allows the EC to rebuild its internal counters against the new cell chemistry and clear the false warning.
Z450-series laptop shuts down at 20–30% battery shown on screen
This happens when the fuel gauge IC's stored discharge curve no longer matches the actual cell. The old calibration data predicts a gradual voltage slope, but the new cell hits a steeper voltage cliff under combined CPU and display load — dropping below the EC's cutoff threshold before the percentage reaches zero. The fix is straightforward: let Windows deplete the battery fully to hibernate, recharge to 100% without interruption, and repeat once more. After two calibration cycles, the fuel gauge IC maps the correct curve and the early shutdown stops.