Welcome to our store. Your trusted source for batteries and power solutions. Learn more

For support or quotes: sales@batteryweb.com
WELCOME5
BatteryWeb

Panasonic CF-VZSU0EJS Toughbook Replacement Battery 7.6V 4850mAh

Up to 19% off
New arrival
From $103.99 USD $127.99
Shipping calculated at checkout.
Fits Panasonic Toughbook CF-RZ4, CF-RZ5, CF-RZ6, CF-RZ8 laptops; replaces OEM CF-VZSU0EJS.
7.6V, 4850mAh lithium-polymer cell delivers 36.86Wh for full-shift operation on Toughbook ultraportables.
Connector seats flush into the CF-RZ4 battery slot with positive contact alignment; locking tab latches positively.
We bench-tested this cell against the CF-RZ4 charging controller; BMS negotiated correctly on first insertion without handshake errors.
After installation, run one full discharge to hibernation cutoff, then charge uninterrupted to 100% — this resets the BIOS battery learn cycle and clears inaccurate health warnings that appear after every cell swap.
Delivery time

This product ships directly from our Manufacturer’s Warehouse and is usually delivered within 5 – 8 business days to your doorstep.

Discount: As a thank you for your patience, enjoy 5% off on your order
WECARE5
Visa Mastercard American Express PayPal Apple Pay Google Pay Shop Pay Discover Klarna Afterpay Stripe
✦

Check that your old battery model number and device model to match our description. This makes sure they work together.

✦

We ship your order same day if you buy it before 4 PM EST.

Warranty

Let customers speak for us

from 11 reviews

Product is exactly as described and arrived quickly

Robert Jones
Rocket ES4-12 Compatible Replacement Battery

It took a bit longer than expected, likely due to the holiday season, but that was understandable. So far, the battery seems to be working well!

Linda M.
MGE UPS Systems Pulsar EX 1500RT Compatible Replacement Battery By Bright Way

Excellent substitute for the original, appearing to be the perfect replacement.

Alberto J.
APC SMART-UPS RT SURTA3000RMXL3U UPS High Performance Replacement Battery Set

It was what i was looking for. Support is fast

Jaswal
WAHEGURUG - RADHASWAMI

Fast service

Mark Casias
BatteryWeb

Perfect fit

Mark Casias
STX20L-BS Battery for Harley Softail FLS FLST 1991-2017 High Performance

Works Perfectly!!

Ben Benson
Invacare 220 Scooter High Performance Medical Replacement Battery Set

Send Your Battery Photo

Expert Technician Help

Snap a photo or video of your battery and send it to us. We'll identify the exact replacement—fast and hassle-free. Our team has helped thousands of customers find the right battery quickly and easily.

POST YOUR BATTERY IMAGE
Product & Solutions Expert

Product & Solutions Expert

✉ sales@batteryweb.com

🔹 10+ Years Battery Experience 🔹 Fast & Accurate Identification

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

7.6V

Amp

4850mAh

Panasonic CF-RZ4 / CF-RZ8 Series — 7.6V Li-Polymer Replacement Battery (CF-VZSU0EJS)

This 7.6V, 4850mAh (36.86Wh) lithium-polymer battery replaces the CF-VZSU0EJS cell in the Panasonic Toughbook CF-RZ4, CF-RZ5, CF-RZ6, and CF-RZ8. These are compact rugged ultraportables used in field and enterprise environments where a degraded cell kills portability fast. Voltage and capacity match OEM spec exactly — no firmware workarounds needed.

  • CF-RZ4 through CF-RZ8 compatibility: All four models share the same 7.6V Li-Polymer cell format, connector pinout, and BMS handshake protocol — Panasonic carried the same battery platform across this rugged ultraportable line without changing the charge circuit.
  • Bench tested on actual hardware: We cycled this cell through the CF-RZ4 charge controller and confirmed the BMS negotiated correctly, accepted a full charge, and released discharge current without triggering a protection cutoff.
  • Post-install calibration cycle on the CF-RZ4: 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 the CF-RZ series throws after every cell swap.

Why the CF-RZ4 BIOS reports poor battery health after a cell swap

The CF-RZ series stores charge history and health metrics in EEPROM on the battery pack itself. When you fit a new cell, the BIOS reads that blank EEPROM and flags the battery as unknown or degraded — not because the cell is faulty, but because no history exists yet. Running the calibration cycle writes initial data to the fuel gauge IC and gives the BIOS something real to read. After two to three full cycles, the health flag clears and the reported capacity stabilises.

CF-RZ4 shutting down at 20–30% charge shown on screen

This happens when the fuel gauge IC has not yet calibrated against the new cell's actual voltage curve. The OS reads the old curve, thinks 25% is safe, but the cell voltage drops below the BMS cutoff threshold under combined CPU and display load — and the system cuts out. It is not a faulty cell. Run one full discharge to hibernate-cutoff without interruption, then charge to 100%. That single cycle gives the fuel gauge IC enough data to remap the curve accurately to the new cell.

Compatible Models

CF-RZ4 CF-RZ5 CF-RZ6 CF-RZ8

Replaces Part Numbers

CF-VZSU0EJS

Technical Specifications

Voltage7.6V
Amp Hours4850mAh
Capacity4850mAh
Rate36.86Wh
Net Weight178g /6.28 oz
Gross Weight318g /11.22 oz
Approximate Weight318g /11.22 oz
Dimension 183.20 x 80.00 x 9.40mm

Product Highlights

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

Frequently Asked Questions

The CF-RZ4 is showing the wrong Wh rating in system information after fitting this battery — is something wrong with the cell?

Nothing is wrong with the cell. The Wh value displayed in system information is pulled from EEPROM data stored on the battery pack, not measured in real time. A new cell ships with blank or default EEPROM, so the system may report a figure that does not match the rated 36.86Wh. Run two full charge and discharge cycles and the fuel gauge IC will write calibrated data — the displayed Wh reading will settle to an accurate figure after that.

The CF-RZ5 stopped charging above 80% after I installed this replacement — what's causing it?

This is almost always a BIOS-controlled charge limit, not a fault with the cell. Panasonic's battery management firmware on the CF-RZ series includes a charge threshold setting that caps charging at 80% to reduce cell wear during long periods on AC power. Check the Panasonic Power Plan Extension utility or BIOS battery settings and confirm the charge limit is set to 100%. Once that setting is corrected, the cell will charge fully.

The OS fuel gauge is jumping around wildly — showing 60%, then 90%, then 45% within minutes on the CF-RZ6

The fuel gauge IC on the CF-RZ6 calibrates against the discharge profile of the previous cell. When a new cell is fitted, the IC has no reference curve and produces erratic readings for the first few cycles. This is not a hardware fault. Run two to three complete discharge-to-hibernate-cutoff and full-charge cycles without interrupting either phase, and the gauge IC will lock onto the new cell's voltage curve — readings will stabilise around cycle three.

Payment & Security

Payment methods

  • American Express
  • Apple Pay
  • Diners Club
  • Discover
  • Google Pay
  • Mastercard
  • PayPal
  • Shop Pay
  • Visa

Your payment information is processed securely. We do not store credit card details nor have access to your credit card information.

Related Products

Panasonic CF-RZ4 Replacement Battery, 7.6V, 4850mAh, Li-Polymer 1

Engineered for Performance. Built to Last.

Check out our top-rated selection of reliable products built to last. We offer high-quality options that deliver consistent performance for all your needs.

Our Collections