Calculating Battery Backup Time - Nortel DMS-100 Series Maintenance Manual

Calculating battery backup time

Use these values to calculate approximate battery backup time for the
different configurations. Use the following steps complete the calculation:
1 Calculate the total battery power reserve.
— An- Eagle Picher battery at an 8-hour discharge rate is 46.4 Ah
capacity. A 46.4 Ah/string x 6 strings is 278.4 Ah total backup
power. The end of life capacity of the batteries is 80%. Derate the
reserve power to give a worst case description as follows:
– 278.4 Ah x 0.80 is 222.72 Ah backup power
2 Divide the total backup power by the frame power demand to obtain the
estimated backup time as in the following example:
– six strings of Eagle-Picher batteries at 80% are 222.72 Ah
– OPAC configured with 640 lines at 3.0 CCS is 20.32 A
Estimated backup time is (222.72 Ah) / (20.32 A) is 8.2 h.
The estimated backup times for OPACs with 222 Ah of reserve power
available appear in the following table. The OPACs in this example have a
call rate of 3.0 CCS.
Reserve power estimates for 3.0 CCS call rate
Drawers
0
1
Note 1: The above values ( 15 percent) provide a good estimate of backup
power and times.
Note 2: The above calculations do not include the following factors:
— line card types other than NT6X17AA (most other line cards draw less
power)
— increase in battery current drawn by system packs as the battery voltage
drops from –52 V dc down through –42 V dc
— decrease in loop current drawn by lines as the battery voltage drops from
–52 V dc down through –42 V dc
Total frame
demand (A)
short average
Lines
loops
0 : 12.00
64 12.84 : 12.62
DMS-100 Family OPAC Maintenance Manual XPM12 and up
OPAC maintenance overview 2-33
Estimated
backup time
Estimated
backup time (hours) short
loops: average
(hours) short
loops with
loops: average
additional 15 A
loops without
load
additional load
: 18.6 : 8.2
17.3 : 17.6 8.0 : 8.1