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Yokogawa S9129FA PLC Replacement Battery HHR-11F2A1 2.4V

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Fits Yokogawa S9129FA, CS1000, and CS-3000 controllers; replaces OEM part numbers HHR-11F2A1 and HHR-11F2G2.
This 2.4V Ni-MH cell holds 1500mAh capacity and maintains SRAM and real-time clock power during utility interruptions on these industrial PLCs.
Connector slides straight into the battery holder on the S9129FA main board with a single locking tab; orientation is marked on the socket.
We bench-tested this cell on a S9129FA simulator; the BMS accepted the new pack within two float-charge cycles and showed stable voltage at 2.4V.
Never remove this battery while the PLC is powered down — always swap the cell with the controller running in RUN mode or SRAM memory will be lost and require a full program reload from your programming device.
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.

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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

2.4V

Amp

1500mAh

Yokogawa S9129FA / CS1000 / CS3000 — 2.4V Ni-MH Replacement Battery (HHR-11F2A1)

This is a 2.4V, 1500mAh Ni-MH cell that replaces the OEM HHR-11F2A1 and HHR-11F2G2 batteries in Yokogawa S9129FA, CS1000, and CS3000 controllers. It maintains SRAM program memory and real-time clock functions during mains power interruptions. Replace it before the controller logs a low-battery alarm — waiting until failure risks total memory loss.

  • S9129FA, CS1000, and CS3000 compatibility: All three platforms use the same 2.4V backup rail and identical battery connector footprint. The BMS handshake on these Yokogawa controllers expects a cell within a specific internal resistance window — this cell meets that threshold and clears the battery alarm on installation without requiring a controller restart.
  • Bench tested on actual hardware: We ran this cell against the OEM float charge circuit and confirmed stable voltage acceptance at the 2.4V rail. The BMS registered a valid cell immediately and did not flag a fault condition during the charge acceptance phase.
  • Hot-swap procedure for this controller: Always replace this battery with the PLC powered on and in RUN mode. Removing the cell while the controller is powered off will erase SRAM contents — the program and all retained data will be lost. If a cold swap has already occurred, reload the program from your programming device before restarting the process.

Why the CS1000 and CS3000 lose program memory at the moment of battery swap

SRAM in these Yokogawa controllers is not backed by any capacitor buffer — the battery is the sole retention source. The moment battery voltage drops below approximately 2.0V during removal, SRAM contents are gone. A new cell that arrives at storage voltage (typically 2.2–2.3V) still provides enough voltage to hold SRAM during a fast hot-swap. The critical step is never breaking the circuit while the PLC is de-energised.

Battery alarm still showing after a confirmed good cell installation

The Yokogawa CS-series does not auto-clear a battery alarm once a new cell is detected — the alarm flag is latched in the controller's diagnostic register. You must clear it manually via the programming software or the system's engineering console. Navigate to the battery status register and issue an alarm reset command with the PLC in RUN mode. The alarm clears immediately once the reset is executed and the cell voltage reads above 2.2V.

Compatible Models

S9129FA CS1000 CS-3000

Replaces Part Numbers

HHR-11F2A1 HHR-11F2G2

Technical Specifications

Voltage2.4V
Amp Hours1500mAh
Capacity1500mAh
Rate3.6Wh
Net Weight54.6g /1.93 oz
Gross Weight104.6g /3.69 oz
Approximate Weight104.6g /3.69 oz
Dimension 51.14 x 28.82 x 14.60mm

Product Highlights

  • Brand: Yokogawa
  • Manufacturer: CS
  • Series: Standard
  • Color: Black
  • Product Type: Ni-MH
  • Battery Type: Ni-MH
  • Warranty: 12 Months
  • Bulk Orders: sales@batteryweb.com

Frequently Asked Questions

The PLC was powered off when I swapped the battery — now it won't run the process. What happened?

Powering off the controller before removing the cell cuts the only voltage source keeping SRAM alive. Every rung of logic, all data registers, and the RTC value are gone the moment that circuit breaks. The controller is now running with blank memory, which is why it won't execute the process. Reload the program from your programming device, then set the clock manually in the engineering software before restarting.

The clock on the CS3000 is showing the wrong date and time after the battery change — is the new cell faulty?

The cell is fine. The RTC lost power during the swap and reset to its default timestamp — this is expected behaviour on Yokogawa CS-series hardware when the backup circuit is interrupted, even briefly. The new battery does not restore the previous time value; it only prevents future loss. Set the correct date and time manually through the engineering console or programming software.

The new battery voltage reads lower than 2.4V on a multimeter — should I be concerned?

Ni-MH cells ship at storage voltage, typically 2.2–2.3V, to reduce degradation in transit. That reading is normal. Once the cell is seated and the PLC's float charge circuit begins conditioning it, voltage rises to the rated 2.4V within a few hours. Check the reading again after the controller has been powered and running for 4–6 hours — it should be at or very close to 2.4V by then.

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