CF-VZSU27A Panasonic Toughbook CF-W2 Compatible Battery 7.4V 6600mAh

Panasonic Toughbook CF-W2 — 7.4V Li-ion Replacement Battery (CF-VZSU27A)

This is a 7.4V, 6600mAh (48.84Wh) Li-ion battery for the Panasonic Toughbook CF-W2 series laptop. It fits the CF-W2AW1AXR, CF-W2BW1AXR, CF-W2BW1HXR, and over 20 additional CF-W2 variants. It replaces OEM part numbers CF-VZSU27A, CF-VZSU27AU, CF-VZSU27AU-EC, and CF-VZSU27U directly.

• CF-W2 series compatibility: All CF-W2 variants share the same battery connector pinout, voltage rail, and BMS handshake protocol. The pack communicates cell health data over the SMBus line — the BIOS reads this on every boot to determine charge state and flag warnings.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a CF-W2 unit. The BMS accepted the cell without fault codes, the charge controller reached full capacity, and the SMBus communication returned correct voltage and temperature readings throughout.
• First-install calibration on the CF-W2: After fitting this battery, run the laptop on battery power until it drops to hibernate cutoff — do not interrupt. Then charge uninterrupted to 100%. This resets the BIOS battery learn cycle and clears the inaccurate health warning that appears after every cell swap.

BIOS reporting poor battery health immediately after swapping the CF-W2 cell

The CF-W2 BIOS reads health data from EEPROM registers stored in the old battery pack. When a new cell goes in, the EEPROM data no longer matches actual cell state — the BIOS flags it as degraded or unknown. This is not a fault with the replacement cell. Running one full discharge-to-hibernate cycle followed by a full uninterrupted charge lets the BIOS relearn the new cell's actual capacity curve. After two to three cycles, the health indicator stabilises.

CF-W2 shutting down abruptly while the gauge still shows 20–30% remaining

This happens when the cell cannot sustain voltage under combined CPU and display load — the terminal voltage drops sharply below the BMS cutoff threshold before the fuel gauge catches up. The fuel gauge IC is calibrated against the old cell's discharge curve, so it reads high until the new cell's curve is learned. On the CF-W2, run two full discharge cycles to hibernate cutoff without interruption. After those cycles, the fuel gauge recalibrates and the 20–30% shutdown stops. If it persists past three cycles, check the BIOS battery status page for a voltage reading below 6.8V at shutdown.