About this replacement
Asus Transformer 3 Pro T303UA / T304UA Series — 7.7V Li-Polymer Replacement Battery (C21N1603)
This is a 7.7V, 4900mAh (37.73Wh) Li-Polymer battery for the Asus Transformer 3 Pro detachable tablet-laptop. It fits the T303UA and T304UA series, including the GN053T, GN063T, BC011R, and GN048T variants. Install it when the original cell no longer holds a charge or causes unexpected shutdowns.
- T303UA / T304UA platform fit: Both series use the same battery bay, connector pinout, and BMS handshake tied to the C21N1603 cell spec. The voltage rail and EEPROM communication protocol are identical across all variants in this cluster, so one cell covers all listed models.
- Bench tested on actual hardware: We ran this cell through a full charge-discharge cycle on a T303UA unit. The BMS accepted the handshake on first boot, the fuel gauge IC began tracking state-of-charge correctly, and charge current tapered normally at top-of-charge.
- Asus Transformer 3 Pro first-cycle reset: After fitting the new cell, run the battery down until the device hibernates, then charge uninterrupted to 100%. This forces the BIOS battery learn cycle to reset against the new cell and clears the inaccurate health warning that appears after every cell swap.
Why the Transformer 3 Pro shuts down at 20–30% after a battery swap
The fuel gauge IC on the T303UA stores discharge curve data calibrated to the old cell. When a new cell is fitted, the IC maps voltage against its old reference table, so the displayed percentage diverges from actual cell voltage. Under full CPU and display load, the cell voltage drops faster than the stale curve predicts, triggering a low-voltage cutoff at what the OS still shows as 20–30%. Running two full discharge-to-hibernate cycles resets the mapping and brings the gauge back in line with the new cell's actual curve.
BIOS reporting battery health as poor immediately after replacement
The BIOS reads health status from EEPROM data written by the original cell's charge controller. After a swap, that EEPROM record reflects the degraded state of the old cell — not the new one. The system flags poor health because it hasn't yet logged a completed charge cycle against the replacement. Complete one full charge to 100% without interruption, then reboot. The BIOS recalculates health from the new cycle data and the warning clears.