3V is sufficient to turn on any LED, but is within its reverse break down voltage rating (that is why I did not use the common 9V battery). Short circuit current is approx. 30mA. I used a 3V lithium ...

Here is a simple tester for Hobbyists. This LED Component tester can test the integrity of electronic components from resistors to ICs before soldering. It reduces the job of testing the components ...