Joule Thief: 24 LEDs on One AAA Battery, 2n2222a
A “working model” JT using the LED module out of a standard Harbor Freight 3-AAA cell flashlight. The original module had all 24 LEDs in parallel; I rewired it to a 12-parallel x 2-series arrangement.
It runs for hours on a single AAA and will run on a battery voltage of just over 0.5 volts. When a battery will no longer run a radio or camera, it will still give plenty of light in this JT!