FDK CR17450-2WK27 PLC Backup Compatible Battery 3V 5000mAh

FDK CR17450-2WK27 / CR17450ER-F2X — 3V Li-MnO2 Replacement Battery

This is a 3V lithium manganese dioxide cell rated at 5000mAh (15Wh), built to the same footprint as the original FDK CR17450-2WK27 and CR17450ER-F2X cells. It fits PLC and industrial controller applications where the battery maintains SRAM program memory and RTC function during mains power loss. Dimensions are 46.60 x 34.00 x 17.10mm — verify against your controller's battery bay before ordering.

• CR17450-2WK27 and CR17450ER-F2X platform: Both part numbers share the same physical cell format, voltage rail, and lead configuration. Controllers spec'd for either will accept this cell without modification to the connector or housing.
• Bench tested on actual hardware: We ran this cell on a PLC float-charge circuit and monitored open-circuit voltage, internal resistance, and BMS handshake behaviour. The cell held stable output under the low-drain continuous draw typical of SRAM retention circuits.
• Hot-swap procedure for SRAM protection: Always replace this battery with the PLC powered on and in RUN mode. Removing the cell while the controller is powered off will cause SRAM to lose its program. If that happens, a full program reload from the connected programming device is required before the controller can return to operation.

PLC losing program memory after battery swap

SRAM in most PLCs has no capacitor backup — the moment the battery is disconnected and the controller loses mains power, memory is gone. Even a brief interruption during a cold swap is enough. The CR17450-2WK27 must be swapped live, with the PLC energised, so SRAM voltage never drops below the retention threshold (typically 2.0–2.5V depending on the controller). If memory was lost, reconnect the programming device, reload the last saved project file, and verify all I/O mapping before returning the controller to RUN mode.

Battery alarm not clearing after a confirmed good installation

Many controllers latch the battery fault flag in firmware — fitting a new cell does not automatically clear it. The alarm stays active until it is manually acknowledged in the programming software or via a specific reset register. On some Siemens and Allen-Bradley platforms, this requires navigating to the diagnostics buffer and clearing the fault entry directly. Check the controller's manual for the exact reset path; the alarm will not self-clear at 3V on a fresh cell alone.