UFC 3 -520-01
June 10, 2002
Apply the following correction factor to the calculated cell size; the calculated cell size is
made 25 percent larger to ensure that it can supply the required load at end of life:
1
Aging Correction Factor =
= 1.25
0.8
E-1.10
The manufacturer specifies battery performance at the reference temperature
of 25 C (77 F). As the battery temperature falls below 25 C (77 F), battery capacity
decreases. As the battery temperature rises above 25 C (77 F), battery capacity
increases. If the expected operating temperature will be less than 25 C (77 F), adjust
the cell size to account for the reduced capacity at the lower temperature. Table E -1
shows the correction factors for different battery temperatures. This table is based on
vented lead-acid cells with a nominal 1.215 specific gravity. For a different specific
gravity, consult the manufacturer to confirm the applicability of these correction factors.
VRLA cells can have a completely different temperature response; consult the
manufacturer for the appropriate temperature correction factors. Nickel-cadmium cells
also require a manufacturer-provided temperature correction factor for low temperature
operation, but the correction factor is not as large as for lead-acid batteries.
Table E -1. Temperature Correction Factors for Vented Lead-Acid Cells (1.215
Specific Gravity)
Electrolyte Cell Size Electrolyte Cell Size
Electrolyte Cell Size
Temperature Correction Temperature Correction
Temperature Correction
(F)
(C)
Factor
(F)
(C)
Factor
(F)
(C)
Factor
25
-3.9
1.520
71 21.7
1.034
85 29.4
0.960
30
-1.1
1.430
72 22.2
1.029
86 30.0
0.956
35
1.7
1.350
73 22.8
1.023
87 30.6
0.952
40
4.4
1.300
74 23.4
1.017
88 31.1
0.948
45
7.2
1.250
75 23.9
1.011
89 31.6
0.944
50 10.0
1.190
76 24.5
1.006
90 32.2
0.940
55 12.8
1.150
77 25.0
1.000
95 35.0
0.930
60 15.6
1.110
78 25.6
0.994
100 37.8
0.910
65 18.3
1.080
79 26.1
0.987
105 40.6
0.890
66 18.9
1.072
80 26.7
0.980
110 43.3
0.880
67 19.4
1.064
81 27.2
0.976
115 46.1
0.870
68 20.0
1.056
82 27.8
0.972
120 48.9
0.860
69 20.6
1.048
83 28.3
0.968
125 51.7
0.850
70 21.1
1.040
84 28.9
0.964
E-1.11
The aging and temperature correction factors account for inevitable aging and
temperature e ffects. The battery is sized for a particular duty cycle and, depending on
the facility, load growth can occur over time. A design margin correction factor can be
applied to provide additional assurance that the battery will meet its future design
requirements. The design margin correction factor also adds a capacity margin to allow
for less-than-optimum battery operating conditions due to improper maintenance, recent
battery discharge, lower than expected operating temperatures, or other effects. Simply
E-3
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