Clevo NB50TK1 Replacement Battery 10.8V 4200mAh Li-ion

Clevo NB50TK1 Series — 10.8V Li-ion Replacement Battery (NB50BAT-6)

This is a 10.8V, 4200mAh (45.36Wh) Li-ion replacement battery for the Clevo NB50BAT-6. It fits the NB50TK1, NB50TJ1, NB50TL, and NB50TZ notebooks. The connector, voltage rail, and BMS communication protocol match the original Clevo specification.

• NB50 series compatibility: The NB50TK1, NB50TJ1, NB50TL, and NB50TZ all share the same battery bay dimensions, 10.8V three-cell configuration, and SMBus BMS handshake. One replacement cell covers all four models without physical or electrical modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on NB50-series hardware. The BMS negotiated correctly over SMBus, the BIOS accepted the cell without flagging an incompatibility error, and the fuel gauge tracked state-of-charge through full cycles.
• First-cycle calibration on the NB50TK1: After installing, run one full discharge until the laptop hibernates on low battery cutoff, then charge uninterrupted to 100%. This gives the fuel gauge IC a clean reference point against the new cell's actual capacity and clears the inaccurate health warning the BIOS logs after every cell swap.

BIOS reporting battery health as poor immediately after swap

The Clevo NB50 BIOS reads health data from EEPROM registers stored on the battery's protection circuit. When a new cell arrives, those registers hold factory default values that don't match real-world charge history — so the BIOS flags poor health before the cell has run a single cycle. This is a data mismatch, not a cell fault. Run one full learn cycle — discharge to hibernate cutoff, then charge uninterrupted to 100% — and the BIOS recalculates health from live cycle data. After that cycle, the health warning clears and the reported value reflects the actual cell state.

Laptop cuts out at 20–30% remaining under CPU and display load

This happens when the cell voltage drops sharply under combined CPU and display load before the fuel gauge reaches 0%. Li-ion cells hit a steep voltage cliff at the low end of the discharge curve, and under high draw the voltage sag crosses the BMS cutoff threshold while the gauge still shows charge remaining. The fuel gauge IC hasn't been calibrated to the new cell's actual curve yet. Run the full discharge-to-hibernate calibration cycle described above — the gauge IC maps the new cell's voltage-to-capacity curve and the premature shutdowns stop. Confirm the cutoff is set correctly by checking that hibernate triggers at or below 10.8V under load.