About this replacement
Samsung ATIV Book 9 Pro (AA-PBUN4NP) — 15.2V Li-Polymer Replacement Battery
This is a 15.2V, 3700mAh (56.24Wh) Li-Polymer battery for the Samsung ATIV Book 9 Pro ultrabook. It fits the NP940Z5L, NP940Z5J, and NP940Z5L-X03US alongside additional NP940 variants sharing the AA-PBUN4NP form factor. Use the OEM part number to confirm fitment before ordering.
- NP940Z5 series compatibility: These models share the same 15.2V four-cell Li-Polymer rail, the same BMS handshake protocol, and the same physical connector orientation. Any NP940Z5 variant listed under AA-PBUN4NP uses identical charging circuitry, so one cell works across the entire sub-family.
- Bench tested on actual hardware: We ran this cell through full charge and discharge cycles on NP940Z5 hardware. The BMS communicated correctly with the system board, accepted charge without tripping over-voltage protection, and reported state-of-charge data to the OS throughout testing.
- Post-install calibration on the ATIV Book 9 Pro: After fitting, 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.
BIOS reporting battery health as poor after replacement on the NP940Z5
The ATIV Book 9 Pro stores charge history in EEPROM on the battery's BMS board. When a new cell arrives, that EEPROM contains factory defaults that don't match the system's learned data from the old cell. The BIOS reads this mismatch as a degraded or unknown battery. Running a full calibration cycle — discharge to cutoff, then a single uninterrupted charge to 100% — allows the BIOS to rewrite its reference data against the new cell and clear the health warning.
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 actual voltage curve. The IC still references the old cell's degraded discharge profile, so it predicts cutoff too early and triggers shutdown before the true minimum is reached. Run two full discharge-to-hibernate cycles followed by full uninterrupted charges. After those cycles, the fuel gauge recalibrates and the OS reads the remaining charge accurately down to the correct cutoff voltage of approximately 11.4V under load.