Issue
What is the Actual SCU Power Requirement and Battery Life expectancy
Environment
I/NET site with Access Control
Cause
SCU Power Requirement information
SCU Battery Life information
Resolution
The current power ratings listed in TCON312 & TCON313 are the indicate maximum power consumption for Agency markings and recommended transformer sizing.
All of the SCU models all have the same supply circuits.
All three models can deliver up to approx 1.2 amps of 13.6V, and .2A of 5V, along with the onboard 3.3V logic load.
The SCU1200 and SCU1280 provide two terminal blocks (TB4 & TB5) which can deliver 13.6V and 5V power out to miscellaneous sensor/detector loads.
The SCU1200 and SCU1280 also support an external a lead acid battery backup.
When this battery is discharged, application of AC power can call for maximum power from the 13.6V supply with the onboard supply limiting 13.6V to the battery and external load to currents up to approx 1.2 amps.
Even if you are not using the external power for sensor/detector power, the battery can pull maximum power during recharge.
If you are NOT using an external battery backup, and you are NOT using the external 13.6v connection (on TB4 & TB5), and you are NOT using the external 5V connection (on TB4 & TB5), then you could assume a reduced 24VAC power consumption as follows.
For the SCU1200, the 24VAC power input would be approximately .1A (2.4VA).
For the SCU1280, the 24VAC power input would vary from about .1A with no relays on, up to approx .3A (7.2VA) with all 8 relay outputs energized.
SCU Battery information:
SCU1284 NiMh Battery Life
The Varta battery datasheet lists the life expectancy for trickle charge applications (which is what the SCU uses) as
6 years (at temp of 20C)
and
3 years (at temp of 45C)
So in typical access control environment we should be around 25C so around the 6 year expectation would be appropriate.
Also, the end of life is frequently interpreted as reaching ½ capacity on a NiMh battery, so it still has memory retention, even at end of life.
