Typical battery sizes
Below is a chart of some battery sizes applicable for powering inverters:
BCI * Group
Battery Voltage, V
Battery AH
27 / 31
12
105
4 D
12
160
8D
12
225
GC2**
6
220
* Battery Council International
** Golf Cart
Reduction in usable capacity at higher discharge rates.
As stated above, the rated capacity of the battery in AH is applicable at a discharge
rate of 20 Hours. As the discharge rate is increased, the usable capacity reduces due
to “Peukert Effect”. This relationship is not linear but is more or less according to the
table below:
Table 1 Battery Capacity versus Rate of Discharge
Hours of Discharge
Usable Capacity
20
100%
10
87%
8
83%
6
75%
5
70%
3
60%
2
50%
1
40%
Using the above table will show that a 100 AH capacity battery will deliver 100% (i.e.
full 100 AH) capacity if it is slowly discharged over 20 hours at the rate of 5 Amperes.
However, if it is discharged at a rate of 50 Amperes then theoretically, it should
provide 100 AH ÷ 50 = 2 hours. However, the Table above shows that for 2 hours
discharge rate, the capacity is reduced to 50% i.e. 50 AH. Therefore, at 50 Ampere
discharge rate the battery will actually last for 50 AH÷50 Amperes = 1 Hour
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