About this replacement
Asus G551 Series — 10.8V Li-ion Replacement Battery (A32N1405)
This is a 10.8V, 4800mAh (51.84Wh) Li-ion battery for the Asus G551 gaming laptop series, including the G551J, G551JK, and G551JM. It uses OEM part number A32N1405 and shares the same connector, cell count, and BMS handshake as the original. Install it when the factory cell no longer holds a usable charge under gaming or full CPU load.
- G551 series fitment: The G551J, G551JK, and G551JM all run the same 10.8V three-cell Li-ion rail with an identical connector and EEPROM handshake. One battery fits the full lineup because Asus standardised the BMS protocol across these variants during the G551 production run.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on G551JM hardware. The BMS handshake completed correctly, the EEPROM reported accurate Wh data to the OS, and the protection circuit tripped cleanly at the low-voltage cutoff threshold without a hard shutdown.
- Post-install calibration on G551: After fitting, run one full discharge to the hibernate cutoff — do not interrupt it — then charge uninterrupted to 100%. This resets the BIOS battery learn cycle and clears the inaccurate health warning that appears on the status bar after every cell swap on G551 hardware.
BIOS reporting poor battery health immediately after fitting a new G551 cell
The G551 BIOS reads health status from EEPROM data written by the previous cell. When a new battery goes in, the BIOS compares its stored discharge history against the new cell's reported state and flags a mismatch as poor health. This is not a fault with the replacement cell — it is stale data from the old pack. Running one full discharge-to-hibernate followed by an uninterrupted charge to 100% rewrites the learn cycle. After two to three of these cycles, the BIOS health indicator updates to reflect actual cell condition.
G551 shutting down at 20–30% remaining under gaming load
Under combined GPU and CPU load, the G551 draws sharp current spikes that push cell voltage below the BMS cutoff threshold faster than the fuel gauge IC can update the percentage shown on screen. The displayed percentage lags actual cell voltage, so the laptop cuts out while the OS still reports charge remaining. This is a voltage cliff — the cell cannot sustain output voltage at high draw rates once capacity dips past a certain point. Confirm the issue by checking battery voltage under load with HWiNFO64; if pack voltage drops below 9.5V during a stress test, the cell is hitting its discharge floor early and the replacement cell resolves it.