Asus Transformer Book Trio TX201 Replacement Battery C21N1313 7.5V

Asus Transformer Book Trio TX201 Series — 7.5V Li-Polymer Replacement Battery (C21N1313)

This 7.5V, 4400mAh (33Wh) lithium-polymer cell replaces the internal battery in the Asus Transformer Book Trio TX201 and TX201LA. The TX201 is a convertible that splits into a detachable touchscreen tablet and keyboard dock. This battery powers the display unit when the two halves are separated or docked together.

• TX201 and TX201LA compatibility: Both models share the same battery bay dimensions, connector pinout, and BMS handshake protocol. The C21N1313 cell works across both variants without any hardware modification.
• Bench tested on actual hardware: We ran charge and discharge cycles on the TX201 platform. The BMS accepted the cell without fault codes, balanced the cells correctly, and held stable voltage through the full discharge curve.
• TX201 fuel gauge reset after install: After fitting this cell, run one full discharge to hibernate cutoff, then charge uninterrupted to 100%. This forces the fuel gauge IC to re-learn the new cell's actual capacity and clears the low-health warning that the BIOS flags after any cell swap.

Why the TX201 BIOS reports poor battery health after a cell replacement

The TX201's BIOS reads health data from EEPROM registers that were written by the original factory cell. When a new cell is installed, those registers still hold the old cell's wear data. The BIOS sees a mismatch between the EEPROM values and the actual cell state, then flags health as poor or unknown. Running one complete discharge-to-hibernate and uninterrupted full charge forces the battery learn cycle to rewrite those registers against the new cell. After one or two full cycles, the reported health status corrects itself.

TX201 shutting down at 20–30% charge shown on screen

This is a voltage cliff symptom. When the original cell ages, its internal resistance rises — under the combined load of the CPU, display, and tablet communication bus, terminal voltage drops sharply before the fuel gauge reaches zero. The OS reads an estimated state of charge, not a live voltage check, so the shutdown arrives well before the percentage reaches 0%. Replace the cell and complete the fuel gauge calibration cycle described above. After calibration, the percentage reading and the actual cutoff voltage should align within a few percent.