Page194 of 544 Sparesplanning
553-3011-100 Standard14.00 January 2002
NTAK76 battery back-up unit
The batteries supplied with the NTAK76 have an average useful life of four
years, meaning the batteries are depleted to 80% of capacity, and backup time
is diminished. After this period of time the batteries should be replaced. For
more information refer to theOption 11C and 11C Mini Fault Clearing (553-
3011-500)The mean time between failures (MTBF) of the NTAK76 without
batteries is 370 years at 25° C.
6.37 6.99 17
6.99 7.62 18
7.62 8.26 19
8.26 8.91 20
8.91 9.57 21
9.57 10.20 22
10.2 10.90 23
10.9 11.50 24
11.5 12.20 25
12.2 12.90 26
12.9 13.60 27
13.6 14.30 28
14.3 15.00 29
15.0 15.80 30
Table 5 9
Number of spares required (Part2 of 2)
NFT values Number
of spares