Mitsubishi Electric MELSEC-KOJIU Instruction Manual page 125

10. MAINTENANCE AND INSPECTION
10.3 Battery Changing Procedure
The battery for memory backup which is used for the KOJ1 U gives alarm (M254) when the
battery voltage (capacity) reduces. Please change the battery within one month after this alarm
is given.
When the battery abnormal relay M254 turns on
I
Turn off the power and remove the basic
I
unit case.
*1
and remove the battery.
Replace the battery within 10 minutes.
S e t a new battery to the case.
Connect the red cable to
(+)
and the blue
cable to
(-1.
Take care of polarity.
Mount the basic unit case and turn on the
power.
1
I
*1 When the battery is changed, the time from when the power is turned off and the battery
is changed to when the power is turned on again should be within 10 minutes. If
it
exceeds 10 minutes, enough care should be taken because the contents of program and
latch function will be cleared.
0
The guides of preventive maintenance are as follows:
1) When the battery is guaranteed within 5 years and the total power cut time is less than
300 days (7200 hours), change the battery in 4 to
5
years.
2) When the battery is guaranteed within 5 years and the total power cut time has exceeded
300 days (7200 hours), calculate the day when the total power cut time will exceed 7200
hours, in terms of the operating hours during one day or one week and also the power cut
time, thus obtaining the time to change the battery.
Example: If the operating time is 10 hours a day (Le. power is stopped for 14 hours
a
day)
and the power is stopped for 2 days (Le. 24 hours) a week,
14 hours x 5 = 70 hours
24 hours x 2 = 48 hours
7200 hours/(70
+
48) hours
=
61 weeks
61 weeks x 7 days/30 days = approx. 14 months
Therefore, change the battery every 14 months.
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