Omron CPM2C Operation Manual page 153

5. To enable the detection of low battery errors, slide the Low Battery Detection
Switch towards the front of the Unit and set bits 12 to 15 of DM 6655 to "0."
Low Battery Detection Switch
Enable
6. Replace the battery cover.
7. Write the next date that the battery should be replaced on the reminder label.
The battery lifetime of the CPU Unit with clock is 2 years at 25  C and that of
the CPU Unit without clock is 5 years at 25°C.
Section 5-7