Asus EeeBook X205 Replacement Battery C21N1414 7.6V 4800mAh

Asus EeeBook X205TA Series — 7.6V Li-Polymer Replacement Battery (C21N1414)

This 7.6V, 4800mAh Li-Polymer cell replaces the OEM battery in the Asus EeeBook X205 and X205TA ultrabook series. It fits the CKSE321D1 configuration and all X205TA variants including the UH01-BK. Capacity is rated at 36.48Wh, matching the original specification.

• X205 and X205TA platform fit: Both models share the same low-profile chassis, identical connector pinout, and the same BMS handshake protocol over the 2-wire SMBus line. A single cell covers the full variant range because the power rail and communication spec never changed across the production run.
• Bench tested on actual hardware: We cycled this cell on an X205TA board. The BMS initialised without fault codes, charge acceptance started immediately at the correct 8.4V cutoff ceiling, and the fuel gauge IC registered the new capacity without manual intervention.
• Post-install recalibration on the X205TA: After fitting, run the battery down until the laptop hibernates on its own, then charge uninterrupted to 100% without using the machine. This lets the BIOS battery learn cycle complete a full reference pass against the new cell and clears the inaccurate health warning that appears after every cell swap.

BIOS reporting poor battery health immediately after fitting a new cell

The X205TA stores battery health data in the embedded controller's EEPROM, not in real-time from the cell itself. When a new cell goes in, the EC compares the new cell's EEPROM registers against the degraded thresholds written by the old battery and flags a mismatch as poor health. This is not a fault with the replacement cell. One complete discharge-to-hibernate followed by a full uninterrupted charge resets the reference baseline and clears the warning. After two or three full cycles, the health readout in Windows and the BIOS will reflect the actual cell state.

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

This happens when the fuel gauge IC still holds calibration data from the old, degraded cell. The percentage shown on screen no longer maps accurately to the actual voltage curve of the new cell. Under full CPU and display load, the new cell reaches a point on its discharge curve that the IC interprets as critically low, and the EC triggers a hard shutdown before the real charge is exhausted. Run two complete discharge-to-hibernate and full charge cycles without interruption. By the third cycle the fuel gauge IC re-maps its reference curve to the new cell and the shutdown behaviour stops — verify by watching the voltage stay above 6.8V under load at the 25% mark.