Samsung NP-Q1U Notebook Replacement Battery 7.4V 4400mAh

Samsung NP-Q1U Series — 7.4V Li-ion Replacement Battery (AA-PB1UC4B)

This 7.4V, 4400mAh Li-ion battery replaces part number AA-PB1UC4B in the Samsung NP-Q1U, NP-Q1 Ultra, NP-Q1U-000, NP-Q1U-A000, and related Q1 variants. It fits directly into the original battery bay without modification. Capacity is 4400mAh (32.56Wh), matching the original cell specification.

• NP-Q1U platform compatibility: The Q1U and Q1 Ultra share a common battery bay footprint and connector pinout across their sub-variants. The BMS handshake uses the same EEPROM authentication data, so this cell communicates correctly with the BIOS on all listed models without triggering an unrecognised-battery warning.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a Q1U unit. The BMS accepted the cell immediately, charge current ramped correctly through CC/CV stages, and the protection circuit tripped as expected at low-voltage cutoff.
• Post-install calibration on the Q1U: After fitting, run the battery down until the laptop hibernates, then charge uninterrupted to 100% without interruption. This forces the Q1U's fuel gauge IC to relearn the new cell's actual capacity curve and clears the inaccurate health warning that appears in Windows after every cell swap.

Why the Q1U BIOS reports poor battery health immediately after a cell swap

The Q1U stores battery health data in EEPROM on the original cell. When a new cell is installed, the BIOS reads stale or mismatched EEPROM values and flags the battery as degraded before any charge cycle has run. This is not a fault with the replacement cell — it reflects the BIOS comparing new chemistry against old stored data. Running one full discharge-to-hibernate followed by a full uninterrupted charge resets the learn cycle and clears the warning on most Q1U firmware versions.

Q1U shutting down abruptly at 20–30% charge shown

This happens when the cell voltage drops sharply under combined CPU and display load — a voltage cliff the fuel gauge IC did not predict correctly. On a freshly installed cell, the gauge IC hasn't yet mapped the new cell's discharge curve, so it misjudges remaining capacity. The laptop cuts out because actual cell voltage hits the BMS protection floor before the percentage readout reaches zero. Two to three full calibration cycles — full discharge to hibernate, full charge to 100% — give the gauge IC enough data to track the curve accurately and stop early shutdowns.