Searching for a method to calculate battery life.

Hello makers,

I'm currently trying to decipher how long my project could last in it's current configuration.

The program is using just 7% of the board's memory and I'm using an arduino Uno R3. The output is just a set of four LED's that serve as a night light using a photoresistor to determine the appropriate moment to switch on and off.

I have left all components working as they normally would, in other words I haven't taken any measures to minimize current consumption aside from programming efficiently.

I'm powering it using a set of six double A batteries and a DC connector.

Any suggestion on how to predict it's lifespan? Or is this an ignorant question?

Many thanks to any who help out.

First thing would be to measure the current flow from the battery using your multimeter.

As you are using the LEDs for light they will probably account for a large part of the energy consumption.

An Uno should run fine from a pack of 3 AA cells (4.5v) connected to the 5v pin. That will avoid energy losses in the step-down from 9v to 5v.

...R

Battery lifetime in hours is approximately equal to battery capacity in mAh divided by device current draw in mA.

Alkaline AA have about 2500 mAh

Arduino Uno R3 draws about 50 mA, so about 2 days.

A bare bones Arduino can be set up to run for years on 2xAA, if you use sleep modes.