Battery Capacity Calculator

There is a limited number of molecules available to react in any charged battery. And, there is a limited amount of charge that a battery can move through a circuit before its energy runs out. Rather than measuring a battery’s capacity in electrons, we use the amp-hour. The amp-hour is a unit of charge, not current; one amp-hour is enough charge for a one-amp current that flows for one hour

Inputs

Battery Life

mAH

Load Current (Consumption of Device)

Output

Battery Capacity Rating

Equations

$$Q = I \cdot t $$

where:

Q is the charge in coulombs (C)

I is the current in amps (A)

t is the time in seconds (t)

The amp-hour value — how much charge is stored in a battery — multiplied by the average battery voltage will provide an estimate of how many watt-hours a battery contains.

$$E = C \cdot Vavg$$

E is energy stored in watt-hours, C is the capacity in amp-hours, and Vavg is the average voltage during the energy discharge.

Application

This calculator computes the capacity-related properties of a battery. The above calculation shows how much battery capacity is required to run a certain device and how many watt-hours the battery holds.