Dell Alienware M11x Compatible Battery 14.8V 4250mAh 312-0984

Dell Alienware M11x Series — 14.8V Li-Polymer Replacement Battery (312-0984)

This is a 14.8V, 4250mAh (62.9Wh) Li-Polymer battery for the Dell Alienware M11x, M11xR2, and M11xR3 gaming laptops. It replaces OEM part numbers including 312-0984, 8P6X6, DKK25, and PT6V8. The battery connects via the original harness with no modification to the chassis.

• M11x, M11xR2, M11xR3 compatibility: All three revisions share the same 14.8V four-cell Li-Polymer architecture and P06T chassis connector. The BMS handshake protocol and EEPROM addressing are identical across all three board revisions, so one part number covers the full run.
• Bench tested on actual hardware: We cycled this cell through full charge and discharge on M11x hardware. The BMS negotiated correctly with the EC, reported state-of-charge accurately in Windows, and held voltage above 14.4V through the full draw of the GPU and display under load.
• Post-install calibration cycle: After fitting, run the laptop on battery until it hits hibernate cutoff, then charge uninterrupted to 100% without unplugging. This completes the BIOS battery learn cycle and clears the inaccurate health warning that appears after every cell swap on the M11x platform.

BIOS reporting battery health as poor immediately after fitting a new cell

The M11x EC reads health data stored in the old cell's EEPROM and compares it against the new cell's charge curve. Until the learn cycle runs, the system flags the new cell as degraded because the logged history does not match observed behaviour. This is not a fault with the replacement cell — it is stale data. Run one full discharge-to-hibernate followed by an uninterrupted charge to 100% and the BIOS health indicator resets to normal.

Laptop shuts down hard at 20–25% charge shown on screen

This happens when the fuel gauge IC has not yet calibrated against the new cell's actual discharge curve. The operating system trusts the old curve, so it predicts remaining capacity incorrectly — the displayed percentage still reads 20% when the cell voltage has already dropped below the EC's cutoff threshold. The fix is two to three full discharge and charge cycles so the fuel gauge IC can map the new cell's voltage-to-capacity profile. After calibration, the shutdown point moves back to 0–3% as intended.