User`s manual

MPS Doc: UPS_AS_UM Rev (-) May 23, 2012 Page 25 of 38
Assuming that the “Low Charge Warning” will be a sufficient visual warning and a
no additional warning will is required before Shutdown; we will set the “Windows
Shutdown Delay" to its minimum i.e. 10 sec.
It means that we should set the "Low Charge Shutdown Threshold" such that it will
ensure 2 minutes (the actual shut down time of the server) plus 10 second (the
“Windows Shutdown Delay” that we will enter) of battery operation at 500W (the
Server consumption).
Leaving 25% of the theoretical 100% charge of the battery as a “safety margin” (to
account for battery aging, inaccuracy of the battery monitor, etc,) we will set the
“Low Charge Shutdown Threshold” to 35%:
(2.15/35) x 100% + 25%= 31% => 35%.
The 2.15 above is the 2 minutes plus 10 seconds that the battery must be able to
provide in order to ensure safe shutdown. The 35 is the holdup time that the
battery can support at 500W loading (from the “M359-1 Holdup Time Vs Power”
plot) and the 25% is the safety margin.
5.2.2. In order to provide a 5 minutes early warning, the "Low Charge Warning
Threshold" will have to set at 14% above the Shutdown threshold:
(5/35) x 100% = 14%
We will set the "Low Charge Warning Threshold" to 35% +14% = 49% =>55%
(The Charge Levels can be entered only as odd number multiplication of 5%).
5.2.3. In order to maximize the battery life we will want to shut down the UPS as
soon as the Server has safely shut down, before the battery is fully depleted
(deep discharge cycles reduce battery life). Since the server will be off
within 2 minutes and 10 seconds after the Shutdown Procedure is triggered
(130 seconds), we will check the “UPS Shutdown” box and enter 250
seconds (130 plus 120 seconds margin) in the “UPS Shutdown Delay” box.
(The 120 second margin have minimal affect on the batteries charge since
once the Server has shut down, the load on the UPS in our example will be
negligible).