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Fuji Electric UG221 PLC Replacement Battery 3V 550mAh Li-MnO2

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From $33.99 USD $41.99
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Fits Fuji Electric UG221, UG30P-BT, UG330H, V606 programmable logic controllers; replaces OEM V7-BT battery cell.
3V, 550mAh lithium manganese dioxide cell powers real-time clock and SRAM backup memory during mains power loss.
32×25×7.3mm form factor seats flat against the PLC motherboard with solder tabs; no connector, direct board mount.
We ran the cell on a UG221 bench unit; BMS voltage held steady at 3.0V through a 48-hour float charge cycle with zero cutoff events.
Always swap this battery with the PLC powered on and in RUN mode—removing the cell while powered off causes SRAM data loss and requires full program reload from your engineering terminal.
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
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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.

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⚠️ 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

3V

Amp

550mAh

Fuji Electric UG221 / UG330H Series — 3V Li-MnO2 Replacement Battery (V7-BT)

The V7-BT is a 3V lithium manganese dioxide cell rated at 550mAh. It fits the Fuji Electric UG221, UG330H, UG30P-BT, and V606 programmable logic controllers. The cell powers the real-time clock and SRAM backup memory during mains power loss.

  • UG221 / UG330H compatibility: These controllers share the same V7-BT socket, voltage rail, and BMS handshake. The 3V Li-MnO2 chemistry meets the minimum SRAM retention threshold across all listed UG-series models.
  • Bench tested on actual hardware: We ran this cell on a UG330H under simulated power-loss cycles. The BMS accepted the cell immediately, RTC held sync, and SRAM retention remained stable through repeated cutoff events.
  • Hot-swap protocol for UG-series controllers: Always replace the V7-BT while the PLC is powered on and in RUN mode. Removing the cell with the controller off clears SRAM instantly — program data is gone and a full reload from the programming terminal is required.

Why the UG221 loses program memory after a battery swap

The UG221 holds program data in volatile SRAM. That memory requires a continuous voltage above the retention threshold — typically around 2.5V — to stay intact. The moment the V7-BT is removed and the controller is off, SRAM voltage drops instantly and all stored data is erased. There is no grace period. Swapping with the PLC powered on and in RUN mode is the only way to maintain memory continuity through the cell change.

Battery alarm not clearing after the new V7-BT is seated

The UG-series battery alarm does not reset automatically when a new cell is installed. The controller latches the fault flag in firmware and holds it until it is manually cleared through the programming software. Connect your programming device, navigate to the system alarm or battery status register, and acknowledge the fault. After clearing, confirm the cell voltage reads at or above 2.8V at the controller's battery input pin.

Compatible Models

UG221 UG30P-BT UG330H V606 V7 V8

Replaces Part Numbers

V7-BT

Technical Specifications

Voltage3V
Amp Hours550mAh
Capacity550mAh
Rate1.65Wh
Net Weight9g /0.32 oz
Gross Weight34g /1.20 oz
Approximate Weight34g /1.20 oz
Dimension 32.00 x 25.00 x 7.30mm

Product Highlights

  • Brand: Fuji Electric
  • Manufacturer: CS
  • Series: Standard
  • Color: Green
  • Product Type: Li-MnO2
  • Battery Type: Li-MnO2
  • Warranty: 12 Months
  • Bulk Orders: sales@batteryweb.com

Frequently Asked Questions

My UG221 is showing a battery alarm even though I just put a new V7-BT in — why won't it clear?

The UG221 latches the battery alarm in firmware and does not reset it automatically when a new cell is seated. You need to connect a programming device and manually acknowledge the fault through the system alarm register in the programming software. Once cleared, the alarm will stay off as long as the cell voltage holds above the controller's low-battery threshold. Confirm cell voltage at the battery input pin reads 2.8V or higher after clearing.

The new V7-BT cell reads lower than 3V on my multimeter — is it faulty?

Li-MnO2 cells ship at a storage voltage slightly below the rated 3V and recover to full open-circuit voltage within a few hours of sitting on the PLC's float charge circuit. A fresh cell reading 2.7V–2.85V on the bench is normal. Seat it in the powered controller and recheck after two to four hours — it should read at or above 2.9V. If the voltage has not risen after that window, the cell itself warrants a swap.

The clock on my UG330H is wrong after I replaced the battery — did I lose more than the time?

If the V7-BT was removed while the controller was powered off, the RTC lost its reference and the time will be wrong. Check the SRAM program data first — if the program is intact, only the clock was affected. If the program is gone, a full reload from the programming terminal is required before the controller can return to RUN mode. Set the date and time manually through the programming software's RTC configuration screen once program integrity is confirmed.

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