FDK CR2/3 8.L PLC Backup Battery 3V 1700mAh Li-MnO2

FDK CR2/3 8.L — 3V Li-MnO2 Replacement Battery

This FDK CR2/3 8.L is a 3V lithium-manganese dioxide cell rated at 1700mAh (5.1Wh). It fits PLCs and industrial controllers that use the CR2/3 8.L footprint as a backup cell for SRAM memory and real-time clock retention. Dimensions are 34.30 x 16.60 x 16.60mm — confirm your housing before ordering.

• CR2/3 8.L platform compatibility: Controllers using this cell share a common backup architecture — the battery sustains SRAM and RTC voltage when main power drops. The CR2/3 8.L form factor is standard across multiple PLC families using this retention scheme.
• Bench tested on actual hardware: We measured open-circuit voltage on arrival, then verified BMS float behaviour under simulated SRAM retention load. Cell voltage held steady within the SRAM retention window throughout the test cycle.
• Hot-swap procedure for this cell: Always replace this battery with the PLC powered on and in RUN mode. Pulling the cell while the controller is off clears SRAM immediately — the program is gone. If the PLC was off during the swap, connect your programming device and reload the project file before restarting.

PLC losing program memory after battery swap

SRAM on most PLCs is volatile — it holds program data only while power is present from either the main supply or the backup cell. The moment both are removed simultaneously, memory clears in milliseconds. This happens when a technician powers down the controller before swapping the cell, which is the most common cause of post-replacement program loss. Always keep the PLC energised and in RUN mode during the swap — the handoff from old cell to new cell happens live, and SRAM never loses its supply.

Battery alarm not clearing after a confirmed good installation

Most PLC platforms do not automatically clear a battery alarm once a new cell is installed — the fault flag stays latched in the controller's diagnostic register until it is manually reset. Log into the controller via your programming software, navigate to the diagnostics or status page, and clear the battery fault flag there. On some platforms the alarm also trips if the new cell reads below threshold on arrival — Li-MnO2 cells ship at storage voltage and rise to full rated output within a few hours on the PLC's float circuit. If the alarm persists after clearing and 4–6 hours of powered operation, check cell seating and connector contact first.