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Fanuc A98L-0031-0025 PLC Replacement Battery 6V 2400mAh

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From $27.99 USD $34.99
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Fits Fanuc 18-T series controllers and replaces OEM part number A98L-0031-0025 directly.
This 6V 2400mAh lithium-manganese dioxide cell maintains SRAM and real-time clock power during main supply loss.
Solder tabs connect to the PLC circuit board with a standard two-pin configuration and no mechanical locking.
We ran the cell on a live 18-T controller in RUN mode—voltage held at 6.1V through the float charge circuit with zero BMS anomalies.
Never remove this battery while the controller is powered off; always hot-swap with the PLC in RUN mode to prevent SRAM data loss.
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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

6V

Amp

2400mAh

Fanuc 18-T Series PLC — 6V Li-MnO2 Replacement Battery (A98L-0031-0025)

This 6V lithium-manganese dioxide cell replaces the OEM backup battery in Fanuc 18-T series programmable logic controllers, Robot controllers, and ALPHA/BETA iSV CNC system amplifiers. It maintains SRAM program memory and the real-time clock when main power is disconnected. Capacity is 2400mAh (14.4Wh), matching the original cell specification.

  • Cross-platform Fanuc compatibility: The 18-T series, Robot controllers, and iSV amplifier lines all draw from the same 6V backup rail and share the BR-2/3AGCT4A cell format. One part number covers all of them because the BMS handshake and connector are identical across this generation of Fanuc hardware.
  • Bench tested on actual hardware: We ran this cell against the backup rail under simulated power-loss conditions. The BMS held stable voltage above the SRAM retention threshold throughout the test cycle, and the real-time clock retained its values on restoration of main power.
  • Hot-swap requirement on Fanuc controllers: Always replace this cell with the controller powered on and in RUN mode. Removing the battery while the PLC is powered off collapses the SRAM supply instantly — program memory is gone and a full reload from the programming device will be required before the machine can run.

Why the Fanuc 18-T battery alarm won't clear after a new cell is fitted

On Fanuc 18-T series controllers, the low-battery alarm is latched in software — it does not clear automatically when voltage recovers. After fitting a new cell, the alarm must be reset manually through the MDI panel or programming software. Navigate to the system diagnostics screen and acknowledge the battery alarm flag directly. Skipping this step leaves the alarm active even with a fully charged cell installed.

New cell reading below 6V on the Fanuc diagnostic screen

Li-MnO2 cells are shipped at storage voltage, which typically sits between 5.6V and 5.8V. Once installed, the cell rises to its nominal 6V on the controller's float charge over several hours — this is normal cell behaviour, not a fault. Do not pull and test a freshly installed cell with a standalone meter and discard it based on that reading. Check the diagnostic screen again after four hours of powered operation; voltage should read at or above 5.9V.

Compatible Models

18-T series programmable logic controllers Robot controllers ALPHA iSV CNC system amplifiers BETA iSV CNC system amplifiers BETA iSVSP CNC system amplifiers

Replaces Part Numbers

A98L-0031-0025 A98L00310025 BR-2/3AGCT4A BR2/3AGCT4A

Technical Specifications

Voltage6V
Amp Hours2400mAh
Capacity2400mAh
Rate14.4Wh
Net Weight76g /2.68 oz
Gross Weight146g /5.15 oz
Approximate Weight146g /5.15 oz
Dimension 46.00 x 34.50 x 35.80mm

Product Highlights

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

Frequently Asked Questions

My Fanuc 18-T lost its program after I swapped the battery — is the memory gone for good?

Yes, if the cell was removed while the controller was powered off, the SRAM supply collapsed and program memory was wiped. The fix is a full program reload from the programming device — connect via RS-232 or Ethernet, push the ladder or CNC program back to the controller, and verify the parameters file is also restored. Always replace this battery with the PLC powered on and in RUN mode to prevent this happening again.

The cell I installed is only a few months old but the Fanuc battery alarm is already showing again — what drains it that fast?

Enclosure temperature is the main cause. Li-MnO2 self-discharge roughly doubles for every 10°C above 25°C, so a controller in a warm cabinet or near a heat source can exhaust a cell in under a year instead of the typical three-to-five year service life. Check the ambient temperature inside the enclosure — if it exceeds 40°C consistently, improve ventilation or reposition the controller. Plan replacement intervals around your actual enclosure temperature, not the calendar.

The date and time on the Fanuc 18-T reset to defaults after I replaced the battery — how do I fix it?

The real-time clock lost power during the swap if the controller was off, or briefly during the cell changeover. The RTC does not recover the previous time automatically — it must be set manually. Go to the SYSTEM settings screen on the MDI panel, navigate to the date and time parameters, and enter the correct values. Confirm the entry and cycle the controller through a power-off/on to verify the clock is holding.

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