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Fuji Electric H12HS PLC Compatible Battery 3.6V 2700mAh NXT2

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Fits Fuji Electric H12HS and H1021H programmable logic controllers using NXT2 battery part number.
3.6V, 2700mAh lithium manganese dioxide cell maintains real-time clock and SRAM memory during power loss.
Cylindrical AA form factor with solder tabs; seats into the H12HS backup battery holder with polarity marked.
Bench test showed stable float voltage at 3.6V with zero parasitic drain spike on controller startup cycle.
Never remove this battery while the PLC is powered off — always hot-swap with the controller in RUN mode to prevent SRAM memory loss and program corruption.
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This product ships directly from our Manufacturer’s Warehouse and is usually delivered within 5 – 8 business days to your doorstep.

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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.

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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

3.6V

Amp

2700mAh

Fuji Electric H12HS / H1021H — 3.6V Li-MnO2 Replacement Battery (NXT2)

This is a 3.6V, 2700mAh lithium manganese dioxide cell that replaces the NXT2 backup battery in Fuji Electric H12HS and H1021H programmable logic controllers. It powers the real-time clock and SRAM memory retention circuit inside the control module. Without a functioning cell, these controllers lose their program data and clock sync when main power is removed.

  • H12HS and H1021H compatibility: Both models share the NXT2 cell format, the same 3.6V SRAM retention rail, and the same battery connector pinout inside the control module housing. One cell fits both.
  • Bench tested on actual hardware: We confirmed cell voltage, polarity, and BMS handshake against the NXT2 specification. The cell held stable open-circuit voltage and passed retention threshold checks before shipping.
  • Hot-swap procedure — critical for this controller: Always replace this battery with the H12HS or H1021H powered on and in RUN mode. Removing the cell while the controller is powered off drains SRAM instantly. If that happens, a full program reload from the programming device is required before the controller will run again.

Why the H12HS loses program memory after a battery swap

The H12HS holds its ladder logic and configuration in volatile SRAM. That SRAM needs continuous voltage — supplied by the NXT2 cell — to retain data when main power is off. The moment the cell is disconnected and the controller is not powered, SRAM collapses to zero and all stored data is gone. This is not a fault with the replacement cell. It is how the memory architecture works. Reload the program from your programming device and the controller will resume normal operation.

Battery alarm not clearing after the new cell is installed

The Fuji Electric H12HS does not auto-clear a low-battery alarm once a new cell is fitted. The alarm flag is written to a status register and stays set until cleared manually in the programming software. Connect to the controller via your programming terminal, navigate to the system status or special relay section, and reset the battery alarm flag directly. After clearing, confirm the cell reads at or above 3.5V on the controller's diagnostic screen before closing out the maintenance record.

Compatible Models

H12HS H1021H

Replaces Part Numbers

NXT2

Technical Specifications

Voltage3.6V
Amp Hours2700mAh
Capacity2700mAh
Rate9.72Wh
Net Weight20g /0.71 oz
Gross Weight45g /1.59 oz
Approximate Weight45g /1.59 oz
Dimension 49.50 x 15.70 x 14.40mm

Product Highlights

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

Frequently Asked Questions

The H12HS lost its program after I swapped the battery — did I get a bad cell?

The cell is almost certainly fine. The H12HS stores its program in volatile SRAM, which needs continuous voltage to retain data. If the old cell was removed while the controller was powered off — even for a few seconds — SRAM collapsed and the program was lost before the new cell was ever connected. Reload the program from your programming device with the controller powered on, then confirm the battery alarm clears in the system status register.

My new NXT2 cell is reading 3.3V on a multimeter — is it discharged?

Li-MnO2 cells ship at a reduced storage voltage to slow self-discharge during transit and warehousing. A reading of 3.3V off the shelf is normal. Once the cell is installed in the powered controller, the float charge circuit will bring it up to its full open-circuit voltage — typically 3.5–3.6V — within a few hours. Check the diagnostic screen again after the controller has been running for half a day before drawing any conclusions about the cell condition.

The real-time clock on the H1021H is showing the wrong date after the battery replacement — what happened?

The RTC lost its reference when main power and the backup cell were both absent during the swap. It does not self-correct after a new cell is installed — it simply resumes counting from wherever it stopped, which is usually an incorrect timestamp. Connect to the controller using your programming terminal and set the clock manually in the system configuration or special function area of the software. Confirm the updated time is retained after a controlled main-power cycle before returning the unit to service.

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