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Panasonic CF-VZSU42 Laptop Replacement Battery 7.4V 7800mAh

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From $109.99 USD $134.99
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Fits Panasonic CF-R4 Series laptops; replaces OEM CF-VZSU42 and CF-VZSU42U battery packs.
7.4V 7800mAh lithium-ion cell restores full capacity to the Toughbook CF-R4 ultraportable notebook.
Connector seats into the CF-R4 battery bay with a single locking tab on the right edge.
We bench tested this cell against a discharged OEM pack; BMS accepted charge without fault codes.
After installation, run one full discharge to sleep-mode cutoff, then charge uninterrupted to 100% — this resets the BIOS battery learn cycle and clears inaccurate health warnings that appear after cell replacement.
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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-R4 Series — 7.4V Li-ion Replacement Battery (CF-VZSU42)

This 7.4V 7800mAh (57.72Wh) Li-ion battery replaces OEM part CF-VZSU42 and CF-VZSU42U in the Panasonic Toughbook CF-R4 ultraportable series. It fits the CF-R4GC5AXS, CF-R4GW5AXR, CF-R4GW5AXS, and related CF-R4 variants. Cell count, connector pinout, and BMS communication protocol match the original factory specification.

  • CF-R4 series compatibility: All CF-R4 variants share the same 7.4V two-cell architecture, battery bay dimensions, and SMBus BMS handshake — so one cell works across the full model range without modification.
  • Bench tested on actual hardware: We ran this cell on a CF-R4 unit and confirmed the BMS negotiated correctly at first insertion, charge acceptance started at the expected 8.0V threshold, and the BIOS recognised the pack without throwing an unknown-battery error.
  • First-cycle conditioning on the CF-R4: After installing, run the laptop on battery until it shuts down at hibernate-cutoff, then charge uninterrupted to 100%. The CF-R4 BIOS runs a battery learn cycle on this sequence — skipping it leaves the fuel gauge reading EEPROM data from the old cell, which causes the health warning to persist.

Why the CF-R4 BIOS shows "Battery exhausted" or poor health after a cell swap

The CF-R4 stores battery health data in EEPROM on the pack itself. When you fit a new cell, the BIOS reads that fresh EEPROM and flags a mismatch against its stored cycle history — this shows up as a poor-health or "battery exhausted" warning even on a brand-new cell. The fix is a full discharge-to-hibernate followed by an uninterrupted full charge. That sequence triggers the BIOS learn cycle, which rewrites the reference data against the new cell's actual capacity. After two to three complete cycles the health indicator normalises and the warning clears.

Laptop shuts off at 20–30% charge shown on the CF-R4

This is a voltage-cliff failure on an aged original cell, not a fault with a replacement. Under combined CPU and display load, the degraded cell cannot hold voltage above the BMS low-voltage cutoff threshold — the system shuts down before the OS fuel gauge reaches 0%. A replacement cell at full capacity sustains voltage through that load spike. After fitting the new cell, run the full discharge-and-recharge learn cycle so the fuel gauge IC recalibrates its voltage-to-percentage curve against the new chemistry. The cutoff threshold is 6.0V across the two-cell pack.

Compatible Models

CF-R4 Series CF-R4GC5AXS CF-R4GW5AXR CF-R4GW5AXS CF-R4GWCKZBR CF-R4GWCZZBR CF-R4HC4AXS CF-R4HW4AXR CF-R4HW4AXS CF-R4JC4AXS CF-R4JW4AXR CF-R4JW4AXS CF-R5 Series CF-R5KC4AXS CF-R5KW4AXP CF-R5KW4AXR CF-R5KW4AXS CF-R5KWPAXP CF-R5LW4AXR

Replaces Part Numbers

CF-VZSU42 CF-VZSU42U

Technical Specifications

Voltage7.4V
Amp Hours7800mAh
Capacity7800mAh
Rate57.72Wh
Gross Weight150g /5.29 oz
Approximate Weight150g /5.29 oz
Dimension 200.04 x 50.80 x 26.77mm

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-R4 fuel gauge is jumping around — 60%, then 80%, then 45% within minutes of installing the new battery. Is the cell faulty?

The fuel gauge IC on the CF-R4 calibrates its percentage readout against discharge curves stored from the old cell. When a new cell goes in, those curves no longer match the actual chemistry, so the gauge swings wildly. Run two full discharge-to-hibernate cycles followed by uninterrupted charges to 100% — the fuel gauge IC relearns the voltage-to-capacity curve of the new cell and the readings stabilise. This is an IC calibration issue, not a cell defect.

Windows is showing the new battery's capacity as 47Wh in Device Manager, but the cell is rated 57.72Wh — why does the Wh figure look wrong?

The Wh value Windows reads comes from EEPROM data written to the battery pack, not from measuring the actual cells. If the EEPROM was pre-written with a conservative rated-capacity figure rather than the full chemistry capacity, Device Manager will display the lower number. This is a data-field difference, not a capacity shortfall — the cell still delivers its full 57.72Wh under load. Run a full discharge and recharge cycle; some CF-R4 BIOS versions update the reported Wh figure after the learn cycle completes.

The CF-R4 won't charge past 80% — it just stops and the charge LED goes solid green too early.

Some CF-R4 BIOS versions include a charge-limit setting that caps acceptance at 80% to reduce cell stress during long plugged-in sessions. Check the Panasonic PC Settings Utility or BIOS power menu for a "Battery Charge Mode" or "Eco Charge" option — if it's active, the 80% ceiling is intentional firmware behaviour, not a battery fault. Disable that setting, then unplug and replug the AC adapter to restart the charge cycle. The battery should then charge to 8.35V per cell and stop at 100%.

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