About this replacement
Asus VivoBook Pro 14X OLED M7400 — 11.61V Li-Polymer Replacement Battery (C31N2019)
This is an 11.61V, 5400mAh (62.69Wh) lithium-polymer battery for the Asus VivoBook Pro 14X OLED M7400 and compatible VivoBook Pro 15 OLED models. It replaces OEM part number C31N2019. The cell fits the same connector and BMS handshake as the original, so the laptop recognises it without driver changes.
- VivoBook Pro M7400 and M3500QC platform fit: These models share the same 3-cell 11.61V architecture, connector pinout, and BMS communication protocol. One cell design covers the full lineup without modification.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on a VivoBook Pro unit and confirmed the BMS handshake, charge termination at full voltage, and thermal cutoff response all behave as expected with the OEM controller.
- Post-install calibration on the OLED display load: After fitting, run one full discharge to hibernate cutoff, then charge uninterrupted to 100%. The OLED panel draws significantly more power under sustained load than a standard LCD — skipping this step leaves the fuel gauge IC miscalibrated, causing early shutdowns and inaccurate percentage readings.
Laptop shutting down at 20–30% remaining after battery swap
This happens because the fuel gauge IC is still calibrated to the old cell's discharge curve. When the VivoBook Pro draws full load — CPU boost plus the OLED panel at high brightness — the new cell's voltage drops steeply at the lower state-of-charge range. The controller reads that voltage cliff as an imminent cutoff and shuts the system down before the gauge reaches 0%. Run one full discharge to hibernate, then a full uninterrupted charge to 100%, and repeat once more. After two complete cycles, the fuel gauge recalibrates and shutdowns stop occurring above 10%.
BIOS reporting battery health as poor or "unknown" immediately after replacement
The BIOS reads health data from EEPROM registers that the old cell wrote over months of use. A new cell has blank or default EEPROM values, which the firmware interprets as a degraded or unrecognised pack. This is a firmware read issue, not a fault with the replacement cell. To clear it, run the battery learn cycle: discharge fully to hibernate cutoff, then charge uninterrupted to 100%. The BIOS rewrites its health baseline from the new cell's data after one complete cycle and the warning clears.