This simple project is intended to help you in answering the lifelong question "Does this battery have any juice left?". Although popularity of single cell batteries (such as AA, AAA, C and D cell) is diminishing, there are still many small devices like TV remotes, flashlights, and other small portable electronics that run on these forms of power.
In order to make a battery tester, there are a few things you will need:
-Three 560 ohm resistors
-One 2.2k ohm resistor
-One green LED
-One yellow LED
-One red LED
-various jumpers (connecting wires)
-One Arduino Uno R3 Microcontroller with usb cable
This project will cost somewhere in the $30-$40 range, however the most expensive part is the Microcontoller (~$30), which is of course re-programmable so this cost can be displaced over future projects.
These items can be found on easily on Amazon.com or Sparkfun.com