Gigabyte W451U Replacement Battery 11.1V 4400mAh

Gigabyte W451U / W551 Series — 11.1V Li-ion Replacement Battery

This is an 11.1V, 4400mAh (48.84Wh) Li-ion replacement battery for the Gigabyte W451U, W551A, and W551U notebooks. It slots into the same bay as the original and connects to the same charging circuit. Voltage and capacity match the factory spec exactly.

• W451U, W551A, W551U compatibility: All three models share the same 11.1V three-cell battery architecture and use an identical connector and BMS handshake protocol. Swapping between these models works because the charge management IC expects the same voltage rail across the whole series.
• Bench tested on actual hardware: We ran this cell through a full charge-discharge cycle on a W551U. The BMS accepted the pack without error, the fuel gauge IC initialised correctly, and the charge circuit ramped to 100% without triggering a fault cutoff.
• Post-install calibration on the W451U and W551 series: After fitting this battery, let the laptop discharge fully until it hibernates on its own, then charge in one uninterrupted session to 100%. This resets the BIOS battery learn cycle on these Gigabyte models and prevents the false "poor health" warning that appears after any cell swap.

BIOS reporting poor battery health immediately after fitting a new cell

The Gigabyte W451U and W551 series store battery health data in the BIOS separately from the cell itself. When a new cell goes in, that stored data still reflects the old degraded pack. The BIOS reads the EEPROM values, compares them against current charge behaviour, and flags a mismatch as poor health. Running one full discharge-to-hibernate followed by an uninterrupted charge to 100% forces the BIOS to rewrite that data against the new cell's actual performance.

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

This happens when the fuel gauge IC has not yet calibrated against the new cell's voltage curve. The IC is still mapping percentage readouts to the old cell's discharge profile, so it misreads the voltage cliff. Under full CPU and display load, actual cell voltage drops faster than the gauge expects, and the laptop cuts power before the displayed percentage hits zero. Run two full discharge-calibration cycles — discharge to hibernate-cutoff each time, then charge uninterrupted to 100% — and the gauge IC remaps the curve to the new cell. After the second cycle, the shutdown-at-20% behaviour stops.