I am standing here looking at my junk drawer wondering which batteries are dead and which ones ar...

[G+_Jason Perry]

I am standing here looking at my junk drawer wondering which batteries are dead and which ones aren't.

 

First though is an Arduino's analog input and an LCD display could do a great job. My only thought is how do I deal with different voltages in particular ones that are above the Arduino's logic level? Do I just just use a voltage divider and accept the reduced resolution? Does it matter?

 

Probably don't need an LCD screen to tell if it is dead or not, but why would I not want to.

[G+_Black Merc]

Even testing a car battery, a voltage divider would still give great resolution. Say 15v charging, reduced to a third to 5v over a scale of 0-1024 works out 0.014v per. So a good AA will read 102 on the scale, 642 for a good 9v

[G+_Ben Reese]

Not as fun, but this is what I use. AA, AAA, 9V, button cell.

 

HK Digital Battery Tester Volt Checker for 9V 1.5V and AA AAA Cell BT-168D by EB https://www.amazon.com/dp/B007F7Q974/

 

This one ships from China, but there are others for twice the price that ship prime.

[G+_J Miller]

Get yourself a good set of rechargables and get off of filling our landfills with dead batteries.

[G+_Robert Short]

i will always use my meter but measuring on a load resistor or light bulb as doing a load test is best to determine storage capacitie. As alot of batteries will provide full voltage on a battery with only 25% life left when measured unloaded.

i believe a double A battery with a load to show rated voltage for at least 30 sec a 12 car battery should drop bellow 12v after 2 minutes of cranking under normal if not using a battery tester.