Fig. 13 Solar Panel Assembly
1 Bird Roost Guard
2 Mounting Bracket
3 Solar Panel
3.9.3 Battery Backup
The battery provides backup power for the RCU. The battery is of the lead-acid type with a 12 V, 7.2
Ah rating. The battery is protected by a fuse in the cable. If the battery is accidentally reversed the
battery fuse will blow but no damage will be done to the RCU electronics. The battery cable is a
replaceable item in case it is damaged in service.
Note that the battery negative terminal is connected to the ground of the cubicle and is also the 0 V
signal for all the electronic interfaces in the RCU.
The RCU maintains a digital point “Battery Needs to be Replaced” (DPID 2) which indicates that the
battery is at end of life. When this point is set it lights the “Replace Battery” LED on the RCU front
panel and is available for transmission via the SCADA system. When the battery is replaced, refer
page 84, the point is reset and the LED is turned off.
The “Battery Needs to be Replaced” point can be set in a number of ways:
Charging : While recharging the battery after it has had a significant discharge (for example,
when the source has been off for several hours) the total charge put into the battery is monitored
and if it requires excessive charge (indicating the battery is at end of life) the battery replacement
flag is set.
Discharging : When the source supply is off the battery is discharged to power the RCU, both
the electronics and the SCADA radio. During discharging the battery voltage is monitored and
the time taken to drop to a level that indicates 50 % of the battery charge has been consumed is
measured. If this time is too short then it indicates that the battery capacity is severely reduced
and the battery is at end of life and the battery replacement flag is set. This requires the Radio
Average Current to be correctly configured, see the relevant protocol manual for more
information.
Time in Service : After a battery has been replaced the days it spends in service are counted
and when they exceed the Battery Life configuration setting, refer page 96, the battery
replacement flag is set.
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