About this replacement
Samsung NT900X3N Series — 7.6V Li-ion Replacement Battery (AA-PBTN2QT)
This is a 7.6V, 3900mAh (29.64Wh) Li-ion replacement battery for the Samsung Series 9 ultrabook. It fits the NT900X3N-K79W and over 130 compatible NT900X3N and NT901X5N models. The cell matches the original AA-PBTN2QT specification for voltage and capacity.
- NT900X3N and NT901X5N platform fit: These models share the same 7.6V battery rail, connector pinout, and BMS handshake protocol. A single cell covers the full range because Samsung held that specification consistent across the Series 9 refresh cycles.
- Bench tested on actual hardware: We ran this cell through charge, discharge, and BMS communication checks on Series 9 hardware. The BMS accepted the cell, reported charge state correctly, and thermal cutoff triggered at the expected threshold — no abnormal trips recorded.
- Post-install calibration on Series 9: After fitting this cell, run one full discharge down to hibernate-cutoff, then charge uninterrupted to 100%. This resets the BIOS battery learn cycle and clears the inaccurate health warning that appears after swapping cells on these models.
BIOS reporting battery health as poor after fitting the new cell
The Series 9 BIOS reads EEPROM data written by the original cell during its service life. When a new cell is fitted, the BIOS compares the fresh EEPROM against its stored health baseline and flags a mismatch as poor health. This is not a fault with the replacement cell. Run one full discharge-to-hibernate cycle followed by a full uninterrupted charge. After two to three of these calibration cycles, the BIOS health indicator updates to reflect the new cell accurately.
Laptop shuts down at 20–30% charge shown on screen
This happens when the fuel gauge IC has not yet calibrated against the new cell's voltage curve. The OS reads a fuel gauge estimate that was built on the old cell's degraded profile, so it reports 25% when the cell is already near its lower voltage cliff. Under full CPU and display load, that voltage cliff arrives faster than the gauge predicts — the BMS cuts power before the OS can trigger a proper shutdown. Run two full discharge-to-100% charge cycles without interruption. After calibration, the gauge tracks the new cell correctly and the premature cutoff stops.