Omron CP1W-BAT01 PLC Replacement Battery 3V 800mAh

Omron CP1W-BAT01 — 3V Li-MnO2 Replacement Battery

This 3V, 800mAh lithium-manganese dioxide cell replaces the backup battery in Omron CP1W series compact PLCs. It powers the real-time clock and SRAM memory retention during mains power loss. Voltage and capacity match the original cell exactly — 3V, 800mAh (2.4Wh).

• CP1W series compatibility: The CP1W platform uses a single 3V Li-MnO2 cell across its compact CPU units. The BMS in these controllers floats the cell at a fixed trickle charge. Voltage and physical dimensions must match the original — 26.10 x 15.50 x 14.40mm — or the cell won't seat against the contact plate correctly.
• Bench tested on actual hardware: We ran this cell on a CP1W-series unit and confirmed the BMS accepted the charge state without triggering a battery fault alarm. SRAM retention held across a simulated mains dropout with the PLC in RUN mode.
• Hot-swap procedure — critical for this controller: Always swap this battery with the PLC powered on and in RUN mode. The CP1W has no supercapacitor buffer — if the cell is removed while the controller is off, SRAM contents are lost immediately and a full program reload from CX-Programmer or Sysmac Studio will be required.

Why CP1W PLCs lose program memory during a battery swap

The CP1W CPU relies on the battery to hold SRAM contents any time mains power is absent. Unlike some controllers with onboard supercapacitors, the CP1W has no secondary hold-up source. The moment the old cell is removed and before the new one seats, SRAM voltage drops below the retention threshold. At that point, the program, I/O memory table, and scheduled task data are erased. The only recovery is a full program download from your programming device.

Battery alarm still showing after a new cell is installed

Omron CP1W controllers do not auto-clear the battery fault flag after a cell swap. The alarm bit stays latched in the Special Auxiliary Area even when the new cell reads a healthy voltage. Open CX-Programmer, navigate to PLC Memory, and manually clear the Battery Error flag — or cycle the PLC through a controlled power-off with the new cell in place. Confirm the flag is clear and the RTC is showing the correct time before returning the controller to production.