Battery Monitor - IDEC MICROSmart FC6A Series User Manual

5: F S
UNCTIONS AND ETTINGS

Battery Monitor

This section describes the battery monitor function that monitors the voltage of the FC6A Series MICROSmart backup battery.
Function Description
You can know when to change the backup battery before it dies by monitoring its voltage. The battery voltage in mV as measured
after the FC6A Series MICROSmart power is turned on is stored in a special data register (D8056), and the battery level status is
displayed on the battery status LED [BAT]. The battery voltage can also be measured at any time.
If the battery dies, device values are reset to their initial values when the power is turned off. Replace the backup battery before it
dies.
Battery voltage (D8056)
Stores the measured battery voltage in mV. The range of the value is 0 to 3,000. If the value is greater than 3,000, this value is
3,000. The battery voltage fluctuates according to the usage environment.
When the power is turned on, this value is 65,535 until the initial battery voltage measurement has completed.
This value is 0 when there is a measurement error or when there is no battery.
Battery voltage measurement (M8074)
Shows the battery voltage measurement status.
0: Battery voltage measurement completed
1: Battery voltage being measured
The battery voltage can also be measured by writing 1. The measured value in mV is stored in D8056. The value is reset to 0
when the measurement has completed. The battery voltage is automatically measured once when the power is turned on and
stored in D8056. For this reason, Battery Voltage Measurement Flag (M8074) does not normally need to be used.
When Battery Voltage Measurement Flag (M8074) is used to measure the battery voltage, current will temporarily flow
Caution
through the battery for A/D conversion processing inside the PLC. This consumes the battery, so minimize the use of Battery
Voltage Measurement Flag (M8074). In particular, do not use Battery Voltage Measurement Flag (M8074) in ladder
programs that perform constant measurements while running.
Battery level indicator
The status of the battery level is displayed on the battery status LED [BAT] according to the battery voltage value.
Replacing the battery on a regular schedule is recommended, regardless of whether the battery status LED is blinking or on. For
details on the battery life, see "Backup Function" on page 2-17 and "Backup Function" on page 2-55.
Replace the battery immediately when the battery status LED is blinking (1-s cycle).
All-in-One CPU module
Battery Status LED [BAT]
Off
Blinking (1 s cycle)
On
When the main power supply is off and the product is started with USB bus power, the monitoring of Battery Voltage

Caution
(D8056) is performed in the same manner as in the above table.
A general guide for the time it takes Battery Voltage (D8056) to decrease from 2300 to 2000 is approximately 10 days

including the effect of the ambient environment (temperature and humidity) while unpowered and powered. Replace the
battery immediately when the battery status LED is blinking (1-s cycle).
The final voltage of the coin cell is 2000. If a battery that has reached its final voltage (battery status LED is on) is left in

the product for a long period of time, the product may be damaged or malfunction.
5-66
Plus CPU module
PWR
RUN
ERR
SD
BAT
STAT
Condition
Battery voltage (D8056) > 2,300
2,300 ≥ battery voltage (D8056) > 2,000
2,000 ≥ battery voltage (D8056)
FC6A S MICROS
ERIES
Normal
Warning
Dead battery
U ' M FC9Y-B1722
MART SER S ANUAL
Battery Status
Sufficient battery level.
Low battery level. Replace the battery.
The battery is almost dead. Or no battery.