UDG-10114

Months

12

24

95

96

97

98

30

48

99

100

6

0

18

36

42

CapDerateL

CapDerateH

Derate

Value (100 mAh)

Derate Change

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SLUSAA0 – OCTOBER 2010

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4Ah decrease in 0.1 Ah steps = 40 separate steps over 365 days

365 days / 40 decrement steps = one decrement step every 9.1 days

So CapDerateH = 9

Finally, 3 years is 365 days x 3 = 1095 days

So DerateChange = 1095

Note that due to slight rounding errors (12 days instead of 12.1 days, etc.) the actual capacity represented at the

end of any time internal (one year, two years, etc.) may be off by a small fraction.

In the example above, the actual implementation calculates to be as listed below (assuming no changes to FCC

from the learned capacity method occur):

Initial capacity = 100Ah and full charge capacity (FCC) decremented 0.1 Ah every 12 days:

End of year 1 capacity (at day 360) = 100Ah – 3.0Ah = 97Ah and (3.0Ah / 100Ah) = 3%

End of year 2 capacity (at day 732) = 97Ah – 3.1 Ah = 93.9Ah and (3.1 Ah / 93.9Ah) = 3.3%

End of year 3 capacity (at day 1095) = 93.9Ah – 3.0Ah = 90.9Ah and (3.0Ah / 90.9Ah) = 3.3%

Total from time 0 to Year 3: (100Ah – 90.9Ah) / 100Ah = 9.1% / 3 years = 3.033%/year

Figure 1 shows how the FCC decreases with time and how the parameters control this. Note that the parameter

values used in Figure 1 are different from the values used in the previous example.

Figure 1. Age Based Capacity Method

8

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