Joule Thief Blocking Oscillator - Toroid winding tricks for low voltage

I'm winding a tiny toroid bead from a broken CFL lamp. I did 10 turns of twisted pair hookup wire. I'm trying to run a blue LED off a dead AA battery that reads 0.8V. The transistor is a 2N3904. The LED flashes but doesn't stay bright. Any suggestions?

Try increasing the number of turns. 10 is a bit low for blue LEDs which have a high forward voltage (~3.2V). Try 15 to 20 turns. Also, check the base resistor. If it's too high (like 10k), the transistor won't saturate. Try a 1k resistor or even a 470 ohm resistor to let more base current through.

Thanks! I rewound the toroid with 18 turns and swapped the resistor for a 1k ohm. The blue LED is now glowing incredibly bright, drawing only 45mA from my dead battery. The transistor stays cool to the touch. This circuit is magic!