GE Fanuc Series1 PLC Replacement Battery 3V 2500mAh

GE Fanuc Series1 — 3V Li-MnO2 Replacement Battery

This is a 3V, 2500mAh lithium-manganese dioxide cell for the GE Fanuc Series1 PLC. It powers the real-time clock and SRAM backup memory in the controller. When this cell fails, the PLC loses program data and clock accuracy the moment main power drops.

• Fanuc Series1 PLC platform: The Series1 controller draws a continuous low-level current from this cell to hold SRAM state and keep the RTC ticking. The 3V Li-MnO2 chemistry holds a flat discharge curve across the cell's service life, which matters because the SRAM retention threshold sits close to 2.8V — a sloping cell gives no warning before data is lost.
• Bench tested on actual hardware: We ran this cell under simulated SRAM and RTC load. The BMS held delivery voltage within spec across the full draw profile. No voltage dropout was observed at the retention threshold.
• Hot-swap procedure — critical for Series1: Always replace this cell with the PLC powered on and in RUN mode. Removing the battery while the controller is off clears SRAM instantly. If that happens, you will need to reload the full program from a programming device before the PLC will run again.

Why the Fanuc Series1 loses program memory after a battery swap

The Series1 uses SRAM for program storage, and SRAM needs continuous voltage to retain data — it is not flash memory. Pull the battery with the PLC off and the SRAM loses power immediately, taking your ladder logic with it. The only recovery path is a full program download from the programming terminal. This is why the hot-swap procedure exists: keep the controller powered on during the cell change so the SRAM stays live the entire time the battery is out.

Battery alarm not clearing after a confirmed good cell installation

The Series1 battery alarm does not reset automatically once a new cell is installed. The fault flag is latched in software and must be cleared manually through the programming software after the swap. Confirm the new cell is seated and reading above 2.9V at the connector, then issue the alarm reset command from the programming terminal. If the alarm returns within hours, check enclosure temperature — ambient heat above 40°C accelerates self-discharge and can trigger the low-battery threshold faster than expected.