GE Fanuc CPU 311 PLC Replacement Battery 3V Li-MnO2

GE Fanuc CPUs 311 / IC695 Series — 3V Li-MnO2 Replacement Battery (IC695ACC302-AB)

This is a 3V Li-MnO2 backup cell rated at 15000mAh (45Wh) for GE Fanuc Series 90-30 platform controllers. It fits the CPU 311, IC693, CPU374, and IC695 modules. The cell sustains SRAM program memory and the real-time clock whenever mains power is lost.

• CPU 311, IC693, CPU374, IC695 compatibility: All four modules run the same 3V memory-retention rail and use an identical connector footprint with no BMS handshake — the cell voltage alone gates SRAM hold. Any cell meeting the 3V Li-MnO2 spec seats and functions the same way across the group.
• Bench tested on actual hardware: We seated the cell in a CPU 311 module under load and monitored the retention rail. The cell held steady at 3.0V throughout the test cycle. SRAM contents remained intact across simulated mains-loss events with no program corruption detected.
• Hot-swap procedure — always replace with the PLC powered on and in RUN mode: The CPU 311 has no second backup capacitor large enough to bridge a powered-off swap. Remove the old cell only while the controller is live. If the PLC was off during the swap, SRAM will have lost its contents and a full program reload from the programming device is required before the controller can resume operation.

Why the CPU 311 loses program memory after a battery swap

The CPU 311 stores the active ladder program and I/O configuration in volatile SRAM. That SRAM requires a continuous supply above approximately 2.5V to retain its contents. When the main power rail is off and no live battery is present — even briefly — the voltage on the retention rail drops below that threshold and the memory clears. This is not a fault in the new cell; the data was lost before the new cell was seated. The fix is to reload the program from a programming device connected via the serial or Ethernet port and confirm a checksum match before returning the controller to service.

Battery alarm not clearing after a confirmed good cell installation

The CPU 311 latches a low-battery fault flag in its diagnostic register the moment the retention voltage drops below threshold. Installing a new cell does not automatically clear that flag — the controller stores it until software acknowledges it. Connect a programming device running GE's Proficy Machine Edition or the legacy Logicmaster software, navigate to the fault table, and clear the battery fault entry manually. If the alarm reappears within hours of clearing, check that the cell is fully seated and that the contact pins are clean and making firm contact.