Appendix 4 Battery Life - Mitsubishi Electric Q26UD(E)HCPU User Manual

Appendix 4
The batteries installed on the CPU module and SRAM card are used to retain data in the program memory, standard
RAM (including an extended SRAM cassette), and latch devices during the power failure. Special relays SM51 and
SM52 turn on due to the battery voltage drop. Even if the special relays turn on, the program and retained data are not
deleted immediately.
After the special relay SM51 turns on, replace the battery quickly within the backup power time for three minutes.
SM51 turns on when the battery voltage drops below the specified value, and remains on even after the voltage is recovered
to the normal value.
SM52 turns on when the battery voltage drops below the specified value, and turns off when the voltage is recovered to the
normal value.
After SM51 and/or SM52 turns on, replace the battery quickly.
SM51 and SM52 turn on when the battery voltage of the CPU module or SRAM card is lowered.
To identify the specific battery of the memory of which voltage is lowered, check the contents of the special resisters
SD51 and SD52.
b15
SD51, SD52
For details of SD51 and SD52, refer to Page 506, Appendix 3.
● As long as the programmable controller is powered on, the data is retained regardless of the installation status of a
battery.
● A battery of the CPU module cannot retain data in the SRAM card.
A battery of the SRAM card cannot retain data in the CPU module.
600
Battery Life
to b4 b3 b2 b1 b0
Fixed at 0
Battery error for CPU module
Battery alarm for SRAM card
Battery error for SRAM card
When the battery
voltage is low, the
value is "1."