NEC Versa AX 14.8V Replacement Battery 4400mAh Li-ion

NEC Versa AX / Versa Note Series — 14.8V Li-ion Replacement Battery (A44 / 21-91026-50)

This is a 14.8V, 4400mAh (65.12Wh) Li-ion battery for the NEC Versa AX, Versa Note, and Versa Note ES notebook computers. It replaces OEM part numbers A44 and 21-91026-50. Fit these cells when the original pack no longer holds a charge or the laptop won't run on battery alone.

• Versa AX and Versa Note compatibility: These models share the same 14.8V four-cell serial battery rail, connector pinout, and BMS handshake protocol — one cell pack covers both product lines without modification.
• Bench tested on actual hardware: We ran charge and discharge cycles on this cell with the Versa Note ES. The BMS accepted the full charge cycle, balanced cells correctly, and reported accurate state-of-charge to the OS fuel gauge by the second cycle.
• Post-install discharge cycle on the Versa AX: After fitting this cell, run one full discharge to the hibernate cutoff, then charge uninterrupted to 100%. This forces the BIOS battery learn cycle to reset against the new cell and clears the inaccurate health warning that appears after every cell swap.

Why the Versa AX BIOS reports battery health as poor after a cell swap

The Versa AX BIOS stores battery health data in EEPROM tied to the original pack's charge history. When a new cell goes in, that stored data no longer matches the actual cell capacity, so the BIOS flags health as poor or unknown. This is not a fault with the replacement cell — it is a calibration mismatch. One full discharge-to-hibernate followed by an uninterrupted charge to 100% resets the learn cycle. After that cycle, BIOS health reporting should return to normal.

Versa Note shutting down at 20–30% charge shown on screen

If the laptop cuts out while the OS still shows 20–30% remaining, the fuel gauge IC has not yet calibrated against the new cell's voltage curve. The old curve data causes the gauge to misread remaining capacity, and the system hits the low-voltage cutoff before the percentage reaches zero. Run two full discharge-to-hibernate cycles followed by full charges with the laptop idle. After those calibration passes, the OS percentage reading will align with actual cell voltage, and shutdowns at false charge levels will stop.