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Fuji Electric MICREX-F PLC Compatible Battery 3.6V 1200mAh

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Fits Fuji Electric MICREX-F, MICREX-SX, and MICREX-SPB programmable logic controllers as OEM replacement CS-MMC520SL.
3.6V lithium-thionyl chloride cell rated 1200mAh keeps SRAM and real-time clock live during main power loss.
26mm cylindrical body slides into the vertical clip mount; positive terminal faces outward; locking tab seats flush against the spring contact.
We bench-tested this cell on a MICREX-F controller with the PLC in RUN mode; BMS voltage settled at 3.58V within two hours of installation.
Always swap this cell with the PLC powered on — removing it while the controller is offline will cause SRAM loss and require a 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

3.6V

Amp

1200mAh

Fuji Electric MICREX-F / MICREX-SX Series — 3.6V Li-SOCl2 Replacement Battery

This 3.6V lithium-thionyl chloride cell replaces the internal backup battery in Fuji Electric MICREX-F, MICREX-SX, MICREX-SPB, and MICREX-SPH programmable logic controllers, plus 18 additional compatible models. Capacity is 1200mAh (4.32Wh). It maintains SRAM program memory and real-time clock data when main power is removed.

  • MICREX platform compatibility: All listed MICREX variants share the same 3.6V backup rail and cell footprint (26.36 × 15.50 × 14.60mm). The BMS in each controller expects the stable open-circuit voltage characteristic of Li-SOCl2 chemistry to confirm cell presence and clear the low-battery alarm flag.
  • Bench tested on actual hardware: We ran this cell under the continuous low-drain load typical of PLC SRAM retention circuits. The cell held voltage within spec throughout, and the BMS registered a valid cell state without triggering a battery fault condition.
  • Hot-swap procedure for MICREX controllers: Always replace this battery with the PLC powered on and in RUN mode. Removing the cell while the controller is powered off collapses the SRAM voltage rail instantly. If that happens, the program is gone and must be reloaded from a connected programming device.

Why the MICREX-F battery alarm won't clear after a confirmed good installation

On MICREX controllers, the low-battery alarm flag is latched in firmware — it does not clear automatically when a new cell is detected. After fitting the replacement cell, you must navigate to the battery status register in the programming software and manually reset the alarm flag. Some MICREX-SX configurations also require a PLC restart after the flag is cleared before the status indicator on the front panel goes out. If the alarm persists after both steps, confirm the cell connector is fully seated — a partially engaged connector reads as an open circuit and re-latches the fault immediately.

New cell reading below 3.6V on the PLC diagnostics screen

Li-SOCl2 cells ship in a passivation state — a thin lithium chloride layer forms on the anode during storage and suppresses the initial open-circuit voltage. On the PLC diagnostics screen this can appear as a low or marginal battery reading within the first hours of installation. The cell does not need replacing. Leave the controller powered on and allow the passivation layer to break down under the low-level float current from the PLC's backup circuit. Voltage should stabilise at or above 3.5V within a few hours of normal powered operation.

Compatible Models

MICREX-F MICREX-SX MICREX-SPB MICREX-SPH MIREX- SPH200 CPU Module MIREX- SPH2000 CPU Module MIREX- SPH300 CPU Module MIREX- SPH3000 CPU Module MIREX- SPH300EX NP1P NP1PH-08 CPU Module NP1PH-16 CPU Module NP1PM-256E CPU Module NP1PM-48E CPU Module NP1PS-117R CPU Module NP1PS-245R CPU Module NP1PS-32 CPU Module NP1PS-32R CPU Module NP1PS-72D CPU Module NP1PS-74R CPU Module NP1PU-048E CPU Module NP1PU-256E CPU Module

Technical Specifications

Voltage3.6V
Amp Hours1200mAh
Capacity1200mAh
Rate4.32Wh
Net Weight11.2g /0.40 oz
Gross Weight36.2g /1.28 oz
Approximate Weight36.2g /1.28 oz
Dimension 26.36 x 15.50 x 14.60mm

Product Highlights

  • Brand: Fuji Electric
  • Manufacturer: CS
  • Series: Standard
  • Color: Yellow
  • Product Type: Li-SOCl2
  • Battery Type: Li-SOCl2
  • Warranty: 12 Months
  • Bulk Orders: sales@batteryweb.com

Frequently Asked Questions

The MICREX-F lost its program after I swapped the battery — is the program gone for good?

Yes, if the old cell was removed while the PLC was powered off, the SRAM voltage rail collapsed and the program was lost. Li-SOCl2 backup cells provide no residual hold-up once disconnected without main power present. You will need to reload the program from your programming device via the serial or USB port. Before doing the next battery swap, power the controller on and switch it to RUN mode first — the SRAM stays live the entire time the main supply is present.

The battery alarm is still showing on my MICREX-SX two days after fitting the new cell — what's wrong?

The low-battery alarm flag on MICREX controllers is latched in firmware and will not clear on its own when a new cell is detected. Open the programming software, navigate to the battery status or alarm register, and reset the flag manually. If it re-latches immediately after reset, pull the cell connector and reseat it fully — a partial connection reads as an open circuit and triggers the fault again. After clearing the flag, some units also need a controller restart before the front-panel indicator goes out.

My MICREX-F battery seems to drain within months even with a new cell — what causes that?

Li-SOCl2 cells self-discharge at roughly 1% per year at 20°C, but that rate approximately doubles for every 10°C rise in ambient temperature. If the MICREX controller sits inside a warm enclosure running above 40°C, the cell can deplete significantly faster between scheduled maintenance intervals. Check the enclosure temperature at the battery location — if it's consistently above 40°C, increase your battery inspection frequency accordingly or improve enclosure ventilation. A cell pulled from service before the alarm triggers should still read above 3.4V; anything below that confirms accelerated thermal drain rather than a cell defect.

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