**C**

_{p}=I^{k}twhere Cp is the capacity of the battery in ampere hours

k is the Peukert's constant

I is the current and

t is the time

The Peukert's Constant k is specified by the manufacturer of the battery and is usually in the range of 1.2 to 2.

Thus the time a battery can provide sustain a certain current without any appreciable drop in voltage would be given by

**t=C**

_{p}/I^{k}Thus a 100Ah capacity with a Peukert's constant of 1.2 will be able to supply a current of 5A for 14.5 hours.