About this replacement
Asus W3 Series — 14.8V Li-ion Replacement Battery (A42-W3)
This is a 14.8V, 4400mAh (65.12Wh) Li-ion replacement battery for the Asus W3 notebook laptop. It fits the W3, W3A, W3N, and W3V model lines. OEM part numbers A42-W3, 90-NCB1B2000, 70-NCB1B1001M, and 90-NCB1B3000 all cross to this cell.
- W3 series compatibility: The W3, W3A, W3N, and W3V all run the same 14.8V four-cell battery rail with an identical connector and BMS handshake. One cell fits the entire platform because Asus held the same charge controller and pack geometry across these variants.
- Bench tested on actual hardware: We cycled this pack through full charge and discharge on the W3 platform. The BMS communicated correctly with the charge controller, accepted a full charge to 16.8V at the cell level, and triggered thermal cutoff within spec under load.
- First-cycle reset on W3 notebooks: After installing this battery, run one full discharge until the laptop hibernates at cutoff, then charge uninterrupted to 100%. This forces the BIOS battery learn cycle to reset against the new cell and clears the false health warning that appears after every pack swap on this platform.
BIOS reporting poor battery health immediately after replacing the W3 pack
The Asus W3 BIOS reads health data from EEPROM stored on the old battery pack. When a new cell is installed, that EEPROM data is gone and the BIOS flags the battery as degraded or unknown. This is not a fault with the replacement cell. Running one complete discharge-to-hibernate followed by a full uninterrupted charge resets the learn cycle. After one to two full cycles, the BIOS health indicator clears and reports accurately.
W3 shutting down at 20–30% charge shown on the fuel gauge
The fuel gauge IC on the W3 platform calibrates its low-voltage cutoff estimate against charge history from the previous cell. With a new pack installed, those historical readings do not match the actual voltage curve of the replacement cell. Under combined CPU and display load, the pack hits a voltage cliff the gauge did not predict, and the system shuts off before the displayed percentage reaches zero. Run two to three full discharge and charge cycles to let the fuel gauge IC recalibrate against the new cell. After calibration, the cutoff should align to approximately 10.5V at the pack level.