About this replacement
Asus AsusPro PU301 Series — 11.1V Li-Polymer Replacement Battery (C31N1318)
This is an 11.1V, 3950mAh (43.85Wh) lithium-polymer replacement battery for the Asus AsusPro PU301 and AsusPro Essential PU301LA series ultrabooks. It replaces OEM part numbers C31N1318 and 0B200-00700000. The connector pinout and BMS handshake match the original so the laptop recognises the pack on first boot.
- PU301 and PU301LA compatibility: The entire PU301 range — including the PU301LA-RO064G and related variants — shares the same three-cell Li-Polymer configuration, 11.1V nominal rail, and SMBus BMS communication line. One cell SKU covers all of them.
- Bench tested on actual hardware: We cycled this pack on a PU301LA unit and logged the BMS handshake across full charge and load discharge. The protection circuit tripped correctly at the low-voltage threshold and the charger IC resumed communication without faults.
- First-cycle calibration on the PU301LA: After installing, run one full discharge until the laptop hibernates, then charge uninterrupted to 100% before using it again. This forces the BIOS battery learn cycle to reset against the new cell data and clears the false "poor health" warning that commonly appears after any cell swap on this platform.
BIOS reporting poor battery health immediately after fitting a new cell
The PU301LA stores charge cycle count and capacity history in the battery EEPROM, not in the laptop firmware. When you fit a new cell, the BIOS reads that EEPROM data as mismatched or blank and flags the pack as degraded before it has run a single cycle. This is a data state issue, not a hardware fault. One complete discharge-to-hibernate followed by a full uninterrupted charge gives the BIOS enough data to recalculate health correctly. After that cycle, the health indicator should return to normal.
Laptop shutting down at 20–30% remaining shown on screen
This is a voltage cliff problem. The fuel gauge IC estimated remaining capacity based on the old cell's discharge curve, so the percentage shown no longer maps accurately to actual cell voltage. Under combined CPU and display load, the cell voltage drops faster than the gauge predicts and hits the BMS low-voltage cutoff while the OS still shows charge remaining. Running two to three full calibration cycles — full discharge to hibernate, full charge to 100% — retrains the fuel gauge IC against the new cell's actual curve. After calibration, the cutoff voltage of 9.0V should align correctly with what the OS reports.