About this replacement
Positivo Master N2140 — 11.4V Li-Polymer Replacement Battery (NV-636668-3S)
This is an 11.4V, 4350mAh (49.59Wh) lithium-polymer battery for the Positivo Master N2140 notebook. It replaces the original NV-636668-3S cell when the factory battery no longer holds charge or fails outright. The connector, cell count, and BMS handshake match the N2140 mainboard directly.
- Master N2140 fitment: The N2140 uses an 11.4V three-cell lithium-polymer configuration tied to a specific BMS communication protocol. This replacement matches that cell arrangement and voltage rail so the mainboard recognises it without firmware rejection.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on the N2140 platform and confirmed the BMS handshake completes correctly. The protection circuit trips at expected undervoltage thresholds and charge termination occurs at full 11.4V.
- Post-install calibration for the N2140: After fitting, run the laptop down to hibernate cutoff under normal use, then charge uninterrupted to 100%. This gives the N2140's fuel gauge IC a clean reference point against the new cell and clears the inaccurate health warning the BIOS throws after every cell swap.
Why the N2140 BIOS flags poor battery health immediately after a cell swap
The N2140's BIOS reads health data from the battery's EEPROM, which holds charge cycle count and capacity history from the previous cell. A new cell installs with either blank or mismatched EEPROM data, so the BIOS interprets it as degraded. This is a data mismatch, not a fault with the replacement. Running one full discharge-to-hibernate then an uninterrupted charge to 100% triggers the battery learn cycle and rewrites the BIOS reference data against the new cell. After that cycle, the health warning clears.
N2140 shutting down at 20–30% shown on the gauge
This happens when the cell voltage drops below the BMS cutoff threshold under load before the fuel gauge reaches zero. On the N2140, running the CPU and display at full draw creates enough current demand to cause a voltage cliff — the cell can't sustain the required rail and the BMS shuts the system down to protect it. The fuel gauge hasn't calibrated to the new cell yet, so the percentage shown at cutoff looks premature. Run two full discharge-to-hibernate cycles and the gauge IC will recalibrate its endpoint to match actual cell voltage. After calibration, shutdown should occur below 5%.