I have a wireless sensor which draws 20mA for 20us and draws 40uA sleep current for rest of the period. The period is 5min. I want to estimate the capacity of the battery which should power the sensor without replacement. Can anybody help me in this by providing some formula or methodology?

 

Wireless battery capacity

 

5 minutes is 300 seconds, and I will ignore the 20 microseconds in the denominator as a simplification.
With the average current and the selected battery’s capacity, you calculate the expected lifetime.

I average =
((20E-03 X 20E-06) + (40E-06 X 300)) / 300
Essentially 40 microamps.

The average current is so low that the battery’s self discharge current could dominate.