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Peukert's Equation
PERCENTAGE OF AVAILABLE CAPACITY FROM A
100 Ah 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: Suppose you have a 200 Ah
battery. Now discharge at a 50-amp
rate until the battery reaches 1.75 V
per cell (10.5 V for a 12 V battery).
This would be equivalent to a discharge
rate of 25 A for a 100 Ah battery. If the
battery delivered 67% (134 Ah) the
appropriate Peukert's exponent would
be 1.25.
Example #2: A 100 Ah battery
with a Peukert's exponent of 1.3
will deliver only 41% of its
capacity when supplying a 100-
amp load.
EXPONENT
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 estimate the
exponent "n" for a battery after a single discharge test. The table is based
on a 100-Ah battery but may be used for any capacity battery by using an
appropriately scaled current. See the examples below: