About this replacement
Samsung NP900X3C Series — 7.4V Li-Polymer Replacement Battery (AA-PBXN4AR)
This is a 7.4V, 5850mAh (43.29Wh) Li-Polymer replacement battery for the Samsung NP900X3C ultrabook. It fits the 900X3C-A01, 900X3C-A01AU, and over 188 confirmed model variants in the 900X3C lineup. The flat 6mm profile matches the original cell geometry inside the ultrabook chassis.
- NP900X3C Series compatibility: Every model in this series runs the same 7.4V two-cell Li-Polymer architecture with the AA-PBXN4AR or AA-PLXN4AR part number. The BMS connector pinout and charge handshake are shared across all 900X3C variants, so one cell covers the full range.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the NP900X3C platform. The BMS handshake completed without error codes, charge termination triggered correctly at 8.4V, and the SMBus communication with the EC remained stable throughout.
- First-cycle calibration on the NP900X3C: After installing, run one full discharge to the hibernate cutoff, then charge uninterrupted to 100%. This forces the BIOS battery learn cycle to re-anchor against the new cell's actual capacity and clears the inaccurate health warning that appears after every cell swap.
BIOS reporting poor battery health immediately after swapping the NP900X3C cell
The NP900X3C reads battery health from EEPROM data embedded in the original cell's fuel gauge IC. When a new cell goes in, that EEPROM registers as either blank or mismatched against the system's stored baseline. Samsung's firmware flags this as degraded health before any real capacity measurement has taken place. The fix is not a hardware fault — it is a learn cycle. Discharge fully to hibernate, charge to 100% without interruption, and the BIOS recalibrates its health metric against the new cell's actual data.
NP900X3C shutting down at 20–30% with no warning after battery replacement
The fuel gauge IC in the NP900X3C tracks remaining capacity using a coulomb counter that was calibrated to the old cell's discharge curve. After a swap, that curve no longer matches, so the gauge reads 25% while the cell voltage is already at the BMS cutoff threshold. The system shuts down because actual cell voltage collapsed — not because the gauge triggered low-battery shutdown. Run two to three full discharge-and-charge cycles to let the coulomb counter re-anchor. After calibration, the gauge should align with actual cutoff at or below 3.0V per cell.