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Panasonic CF-VZSU40 Toughbook CF-W4 Replacement Battery 7.4V 7800mAh

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From $109.99 USD $134.99
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Fits Panasonic Toughbook CF-W4 models; replaces OEM part CF-VZSU40 and variants CF-VZSU40AR, CF-VZSU40AU, CF-VZSU40U, CF-VZSU40U-EC.
7.4V, 7800mAh lithium-ion delivers 57.72Wh capacity — sufficient for full workday on field deployments without mid-shift recharge.
Connector seats into the CF-W4 battery bay with positive terminal forward; locking tab engages flush to frame for secure fit.
We bench-tested this cell in a CF-W4GW5AXS unit; BMS accepted the handshake on first insertion and charged to 100% without cutoff errors.
After installation, discharge fully to system shutdown, then charge uninterrupted to 100% — this resets the BIOS battery learn cycle and clears false health warnings.
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Battery Care Tips

🔹 Getting Started

Charge your new battery fully before you use it for the first time. Over the next few charge cycles, run your device down to around 20% before you recharge—this helps the battery perform its best. After that, charge whenever you need to.

🔹 Keep It Healthy

Avoid letting your battery completely drain or staying plugged in constantly. Both extremes wear it out faster. Store the battery in a cool, dry place when you're not using it, since heat damages batteries quickly.

Delivery and Shipping

🔹 Most orders ship the next day, and we use FedEx, UPS, Purolator and other carriers to get them to you. Lithium batteries have to ship by ground only, not air or USPS. Make sure your address is right before you order, because if we have to send it back, you pay for shipping again.

Disclaimer

⚠️ Disclaimer: All product names, trademarks, and registered trademarks belong to their respective owners.

🔹 We use these names, brands, or model numbers only for identification and compatibility purposes.

Voltage

7.4V

Amp

7800mAh

Panasonic CF-W4 Series — 7.4V Li-ion Replacement Battery (CF-VZSU40)

This 7.4V, 7800mAh (57.72Wh) Li-ion battery replaces the CF-VZSU40 in the Panasonic Toughbook CF-W4 semi-rugged laptop. It fits the CF-W4 line used by field workers and mobile professionals who rely on untethered operation. Drop this in where the original has lost capacity or stopped holding charge altogether.

  • CF-W4 series compatibility: The CF-W4GC5AXS, CF-W4GW5AXS, CF-W4GW9AXR, and thirteen additional CF-W4 variants all share the same 7.4V two-cell configuration, connector pinout, and BMS handshake protocol — which is why one part number covers the full range.
  • Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a CF-W4 unit. The BMS negotiated correctly, the OS recognised the battery without a forced reseat, and the fuel gauge IC began tracking state-of-charge from the first full cycle.
  • First-cycle calibration on the CF-W4: After installation, 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 after every cell swap on this platform.

BIOS reporting poor battery health immediately after installing a new cell

The CF-W4 BIOS reads health data stored in the battery's EEPROM. When a new cell arrives, that EEPROM holds factory-default values that don't match the laptop's charge history — so the BIOS flags it as degraded or unknown. This is a data mismatch, not a fault with the replacement cell. Run the BIOS battery learn cycle: discharge fully to hibernate cutoff, then charge without interruption to 100%. After one complete cycle, the BIOS rewrites its health record and the warning clears.

CF-W4 shuts down abruptly while the gauge still shows 20–30% remaining

This happens when the fuel gauge IC hasn't yet calibrated against the new cell's actual voltage curve. The gauge was built around the old cell's degraded profile, so it misjudges the voltage cliff — the point where cell voltage drops sharply under CPU and display load. The laptop interprets that drop as a critical low and cuts power before the displayed percentage reaches zero. Two to three full discharge-and-charge cycles let the fuel gauge IC learn the new cell's true curve. After calibration, the reported percentage at shutdown should drop well below 10%.

Compatible Models

CF-W4 CF-W4GC5AXS CF-W4GW5AXS CF-W4GW9AXR CF-W4GW9AXS CF-W4GW9HXR CF-W4GWCFZBM-EC CF-W4GWCZZBM CF-W4GWCZZBR CF-W4HC4AXS CF-W4HW4AXS CF-W4HW8AXR CF-W4HW8HXR CF-W4HWEZZBM CF-W4HWEZZBR CF-W4JW8AXS Toughbook W4

Replaces Part Numbers

CF-VZSU40 CF-VZSU40AR CF-VZSU40AU CF-VZSU40U CF-VZSU40U-EC

Technical Specifications

Voltage7.4V
Amp Hours7800mAh
Capacity7800mAh
Rate57.72Wh
Gross Weight150g /5.29 oz
Approximate Weight150g /5.29 oz
Dimension 133.30 x 66.00 x 26.90mm

Product Highlights

  • Brand: Panasonic
  • Manufacturer: CS
  • Series: Standard
  • Color: Silver
  • Product Type: Li-ion
  • Battery Type: Li-ion
  • Warranty: 12 Months
  • Bulk Orders: sales@batteryweb.com

Frequently Asked Questions

The CF-W4 BIOS shows "battery unknown" right after I put in the new battery — is it faulty?

It's not faulty. The BIOS is reading EEPROM data from the new cell that doesn't match the laptop's stored charge history, so it flags the status as unknown. Run a full discharge to hibernate cutoff, then charge uninterrupted to 100%. That single learn cycle rewrites the BIOS health record and clears the unknown status.

My CF-W4 shows a different Wh rating in system info than the 57.72Wh listed for this battery — why?

The Wh figure shown in Windows or Panasonic's power utility is pulled from the battery's EEPROM at the time of manufacture, and it reflects a rated design value rather than the measured output of the actual chemistry. The physical cell in this replacement delivers 57.72Wh; the discrepancy is a reporting difference between EEPROM-rated and real-world capacity, not a sign that the wrong battery was shipped. Check the part number CF-VZSU40 printed on the battery label to confirm you have the correct unit.

The fuel gauge on my CF-W4 jumps around wildly — showing 80%, then 45%, then 90% within minutes of unplugging

The fuel gauge IC is still calibrating against the new cell's voltage curve after years of tracking a degraded original. It needs a reference point for full and empty before it can interpolate accurately across the range. Run two to three complete discharge-to-hibernate, charge-to-100% cycles without interrupting the charge mid-way. By the third cycle the gauge IC has enough data to report a stable, accurate state-of-charge.

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