About this replacement
Asus W7J / M9J Series — 11.1V Li-ion Replacement Battery (A32-M9 / A32-W7)
This is an 11.1V, 4400mAh (48.84Wh) Li-ion battery for Asus W7J and M9J series notebooks. It replaces worn or failed cells under OEM part numbers A32-M9, A32-W7, A33-W7, A33-M9, and several 90-NDT1 / 90-NHQ2 variants. If your original battery no longer holds charge or the system shuts down unexpectedly while unplugged, this is the direct cell replacement.
- W7J, M9J, W7SG, and M9V compatibility: These models share the same three-cell 11.1V architecture, identical connector pinout, and the same BMS handshake protocol — which is why a single cell covers all of them without firmware conflict.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on an M9J unit. The BMS accepted full negotiation, charge current ramped correctly through CC and CV phases, and the protection circuit tripped cleanly at the low-voltage cutoff without needing a manual reset.
- Post-install calibration on the W7J: After fitting this battery, run one full discharge to hibernate-cutoff, then charge uninterrupted to 100%. This resets the BIOS battery learn cycle and clears the inaccurate health warning that appears after every cell swap on this platform.
Why the W7J BIOS reports poor battery health immediately after a cell swap
The W7J BIOS reads health status from EEPROM data written by the original cell during its lifetime. A fresh cell has no accumulated cycle data, so the BIOS interprets blank or mismatched EEPROM values as a degraded battery. This is not a fault with the replacement cell. Running one full discharge-to-hibernate then a complete uninterrupted charge gives the BIOS enough data to rewrite its baseline. After one to two cycles, the health indicator updates to reflect the actual cell state.
Laptop shutting down at 20–30% charge shown on the W7J gauge
This happens when the fuel gauge IC has not yet calibrated against the new cell's discharge curve. The old curve is still in memory, so the percentage reading diverges from actual cell voltage under load — especially when CPU and display draw spikes. The cell voltage drops below the safe cutoff before the gauge reaches zero, triggering a hard shutdown. Run two full discharge-to-hibernate cycles followed by uninterrupted charges to 100%; the gauge IC recalibrates and the shutdowns stop. After calibration, the low-battery warning should trigger accurately at around 10.5V under load.