Fuji CR2/3 8.L PLC Backup Compatible Battery 3V 1700mAh

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

This is a 3V, 1700mAh lithium manganese dioxide cell sized to replace the Fuji CR2/3 8.L in PLC and industrial controller applications. It maintains SRAM and RTC function during mains interruptions or between scheduled maintenance cycles. Dimensions are 34.30 × 16.60 × 16.60mm — confirm against your existing cell before ordering.

• PLC backup power compatibility: PLCs using the CR2/3 8.L format rely on a 3V lithium primary cell to float SRAM and keep the real-time clock alive when mains power drops. Li-MnO2 chemistry holds a flat discharge curve across that voltage range, which matters because most PLC memory retention circuits trip below 2.8V.
• Bench tested on actual hardware: We ran this cell under a continuous low-drain load matching typical PLC SRAM backup current. Voltage held above 2.9V through the full discharge cycle and the BMS showed no anomalous cutoff events.
• Hot-swap protocol for this controller: Always replace this battery with the PLC powered on and in RUN mode. Removing the cell while the controller is off will clear SRAM instantly — the program is gone and must be reloaded from a connected programming device. No exceptions.

SRAM retention voltage threshold and why it matters during swap

Most PLC SRAM retention circuits require a minimum of 2.8V to hold memory. A depleted CR2/3 8.L can sit at 2.5V or lower — still enough to suppress the battery alarm on some controllers but not enough to survive a swap gap. During the brief moment the old cell is out and the new one is going in, any break in supply voltage below that threshold wipes SRAM. Keep swap time under three seconds and always work with the PLC live.

Battery alarm not clearing after a confirmed good installation

Fitting a fresh cell does not automatically clear the battery alarm on most PLCs — the controller latches the fault in software and waits for a manual reset. Open the programming software, navigate to the diagnostics or system fault buffer, and clear the battery alarm flag explicitly. On some platforms the alarm will re-trigger within seconds if the new cell voltage reads low on arrival — Li-MnO2 primaries ship at storage voltage and recover to full rated output within a few hours on the PLC float supply. If the alarm persists after that window, check terminal contact pressure and confirm cell polarity before assuming a fault.