Liebert 1000kVA - Manual (Page 65)

Operation
59
Values for Calculated Total Time and Calculated Time Remaining will appear on the screen approxi-
mately two minutes after the beginning of the discharge event. Calculated Time Remaining also
appears on the Present Status Report screen. Both Calculated Total Time and Calculated Time
Remaining will be updated every six seconds, reflecting actual load changes and battery condition.
When the Calculated Times become available, they will be displayed in place of the Battery Discharg-
ing message on this screen.
Figure 47 Battery time screen (45-minute discharge)
The Battery Time Remaining graph and the Calculated times are extremely helpful to the operator who
has the discretionary authority to order load-shedding activities. The Series 610 automatically samples
battery voltage and load current and recomputes every six seconds. This gives the operator fast and
accurate feedback on efforts to extend battery time remaining by shutting down non-critical loads.
Figure 48 Accuracy range of values for calculated battery times
NOTE
While every effort has been made to make the Rated and Calculated Time Remaining values as
accurate as practical, these values must be regarded as approximations. At the beginning of the
discharge cycle, the Calculated times could be off by as much as ±20% due to such variables as
battery initial charge, age of battery and the subsequent load-shedding activities of the
operator. Within a few minutes, however, these calculations should settle into their design
accuracy of ±10%, with the end-of-discharge tolerance being +0, -10% of actual observed time.
In addition, the operator can adjust the settings affecting Rated Total Time after gaining
experience with the actual battery and connected load.
0 10 20 30 40 50 60
Time (Minutes)
340
360
380
400
420
440
460
480
500
VDC
Battery Shutdown = 417
Battery Charge = 3%
Total 00:45 Remain 0:01
Rated Time (Hrs:Min)
Total 00:25 Remain 0:00
SELECT : MASTER MENU
Low Battery Warning
Calculated Time (Hrs:Min)
0
5
10
15
20
25
0 2.5 5 7.5 10 12.5 15 17.5 20 22.5 25
Elapsed Time (Minutes)
C
alculated Time R
emaining
Upper Limit Actual Lower Limit