Mitsubishi Melsec-Q Series User Manual page 288

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After replacing a battery, write the date for next battery replacement on the sticker on the back side of the front cover.
Write the proper date by checking the battery life. (
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When replacing the battery of a CPU module, pay attention to the following:
• Back up the data in the CPU module by GX Developer before starting replacement.
• When replacing a battery of a Redundant CPU, back up the memory data such as programs by the memory copy
from the control system to the standby system, and then replace the battery of the CPU module that was changed
into the standby status by the system switching function.
For the memory copy from control system to standby system and system switching function, refer to the manual
below.
• When the MELSEC-Q series is used as a UL-certified product, the Q7BAT and Q8BAT battery must be replaced
by service personnel.
The service personnel are defined as experienced technicians who have been sufficiently educated and trained,
and are capable of perceiving and avoiding operational hazard.
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Figure 11.6 Back side of the front cover
QnPRHCPU User's Manual (Redundant System)
Section 11.3.2)