Clevo W840BAT-4 15.12V Replacement Battery 2700mAh Li-ion

Clevo W840SN Series — 15.12V Li-ion Replacement Battery (W840BAT-4)

This is a 15.12V, 2700mAh (40.82Wh) Li-ion replacement battery for the Clevo W840SN notebook. It also fits the W840SU-T, W840AU, and W840SU. OEM part numbers W840BAT-4, 6-87-W840S-4DL1, and 6-87-W840S-4DL2 all cross-reference to this cell.

• W840 platform compatibility: The W840SN, W840SU-T, W840AU, and W840SU share the same 15.12V four-cell architecture and identical connector pinout. The BMS handshake protocol and SMBUS communication line are consistent across all four models, so one cell fits all without modification.
• Bench tested on actual hardware: We cycled this battery through full charge and discharge on the W840SN platform. The BMS held the 15.12V rail steady under combined CPU and display load, and charge termination triggered correctly at capacity without overrun.
• Post-install calibration on the W840 platform: After fitting this cell, 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 in BIOS after every cell swap on W840-series notebooks.

BIOS reporting battery health as poor immediately after swap on the W840SN

The W840SN BIOS reads health status from EEPROM data written by the original cell during its service life. A new cell arrives with a fresh EEPROM, so the BIOS has no charge history to reference and flags the battery as unknown or degraded. This is not a fault with the replacement cell — it is a data gap. Run one complete discharge-to-hibernate followed by a full uninterrupted charge. After two to three cycles the BIOS learn cycle rebuilds its reference table and the health warning clears.

W840SN shutting down abruptly at 20–30% charge shown on screen

The fuel gauge IC on the W840SN estimates remaining charge based on historical discharge curves from the old cell. With a new cell installed, that curve does not match the new chemistry profile, so the gauge reads 20–30% while the cell voltage has already dropped to the BMS cutoff threshold. The laptop shuts down because actual cell voltage has hit the floor, not because the percentage shown is correct. Run two full calibration cycles — discharge to hibernate-cutoff, charge to 100% without interruption — and the fuel gauge IC will recalibrate its curve against the new cell, resolving the early shutdown.