I cleaned up the joule thief wiring and connected it to a 100 Farad supercapacitor which I charged with a pair of garden light solar panels in series. Except for a blocking diode, I did not use any extra circuitry to control the charge.
After a few hours, the capacitor got charged up to 2.83 volt or so, a little over the limit of 2.7v. Nothing blew up and it powered two white LEDs brightly. The joule thief made a buzzing noise which I never noticed until I got closer to it.
As yet, the capacitor makes a poor battery replacement, but the potential is there for a super duper capacitor which can have unlimited cycles of charging.
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