03/03/97
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PERCENTAGE OF AVAILABLE CAPACITY FROM A
100 Ahr BATTERY AT DIFFERENT DISCHARGE RATES
USING DIFFERENT PEUKERT'S EXPONENTS
DISCHARGE RATE IN AMPS
n 5 10 16.7 25 50 75 100 150 200 250 300 400 500
1 100 100 100 100 100 100 100 100 100 100 100 100 100
1.1 100 93 88 85 79 76 74 71 69 67 66 64 63
1.2 100 87 78 72 63 58 55 51 48 46 44 42 40
1.25 100 84 74 67 56 51 47 42 40 37 36 33 32
1.3 100 81 69 62 50 44 41 36 33 31 30 27 25
1.4 100 76 61 52 40 34 30 26 23 21 20 17 16
1.5 100 71 55 45 32 26 22 18 16 14 13 11 10
Example #1: Assume you have a 200
Ahr battery and discharge it at the 50
Amp rate until the battery reaches
1.75V per cell (10.5V for a 12V bat-
tery). This is equivalent to a dis-
charge rate of 25A for a 100 Ahr bat-
tery. If the battery delivered 67%
(134 Ahr) the appropriate Peukert's
exponent would be 1.25.
Example #2: A 100 Ahr bat-
tery with a Peukert's expo-
nent of 1.3 will deliver only
41% of its capacity when
supplying a 100A load.
EXPONENT
HIGH DISCHARGE RATES
& PEUKERT'S EQUATION
The table below may be used to understand the effect of high rates of
discharge on available battery capacity. It may also be used to esti-
mate the exponent "n" for a battery after a single discharge test. The
table is based on a 100 Ahr battery but may be used for any capacity
battery by using an appropriately scaled current. See the examples
below:
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