About this replacement
Samsung 900X4B / 900X4C Series — 7.4V Li-Polymer Replacement Battery (AA-PBXN8AR)
This is a 7.4V, 8400mAh (62.16Wh) lithium-polymer replacement for the Samsung Series 9 ultrabook battery AA-PBXN8AR. It fits the 900X4B-A02, 900X4B-A02US, 900X4B-A03, 900X4C-A04DE, and over 67 additional Series 9 variants. The slim 6.80mm profile matches the original cell geometry for a flush fit inside the chassis.
- Series 9 ultrabook compatibility: All listed 900X4B and 900X4C models share the same 7.4V two-cell Li-Polymer architecture, the AA-PBXN8AR connector pinout, and the same BMS handshake protocol — which is why one cell covers the full variant range.
- Bench tested on actual hardware: We ran this cell through full charge and discharge cycles on a 900X4B chassis. The BMS negotiated correctly, the fuel gauge IC registered the full 62.16Wh capacity, and charge termination triggered cleanly at cutoff voltage.
- Post-install calibration on Series 9: After fitting this cell, run one full discharge until the laptop hibernates at low-battery cutoff, then charge uninterrupted to 100%. This resets the BIOS battery learn cycle and clears the inaccurate health warning that appears on the first boot after every cell swap.
BIOS reporting poor battery health immediately after fitting a new cell
The Series 9 BIOS stores cycle count and health data in the outgoing cell's EEPROM. When a new cell arrives with a fresh EEPROM, the BIOS reads the data mismatch and flags the battery as unknown or degraded — even though the cell is new. This is not a fault with the replacement. Running one full discharge-to-hibernate followed by an uninterrupted charge to 100% completes the BIOS learn cycle and updates the health register. After two to three full cycles, the reported health figure normalises.
Laptop shutting down abruptly at 20–30% charge shown on screen
This happens when the fuel gauge IC has not yet calibrated against the new cell's actual voltage curve. The percentage shown on screen is derived from the old cell's curve, so the displayed value and the real state of charge drift apart — the laptop cuts out before the gauge reaches zero. The fix is two to three full discharge-to-hibernate and full-charge cycles, which lets the fuel gauge IC re-map the new cell's voltage profile. After calibration, the percentage reading tracks the real charge state and the early shutdowns stop.