This is a moment I want to experience the super-capacitors (or supercap, goldcap, supercapacitor, ultracap ...). These are capacitors that have huge storage capacities compared to what we did before (above the Farad, there are some that go up to 3000 farads at 2.7 volts).
So I went on Ebay and I bought a batch of 10 capacitors in Farads 2.7 volts. If we did a little calculation, a capacitor such as this one can store:

E = 1/2 * C * V ² is ½ * 10 * 2.7 ² è 36 Joules is 1 Watt for 36 seconds


But when the capacitors have the same benefits:

• They can load and unload quickly
• They last much longer life (500 cycles max for a battery against over 100,000 for a capacitor)
• They have a much better performance

The first mount I wanted done with a supercapacitor is an LED flashlight. But the big disadvantage of capacitors is that their voltage drops along their dependents. A white LED consumes very little power but needs a minimum voltage of 2 volts to light. A capacitor which has a maximum voltage of 2.7 volts would be helpful if on the beach 2V / V 2.7 is on 25% load.
So I searched for a solution to my problem on the internet and I found a very interesting circuit: the "Joule Thief" (in French: Joule Thief). Most times, it is used to light a LED with a AA battery until the last joule (or almost).

Here is a diagram of a joule thief:
By replacing the battery with the supercapacitor, I thought that it should work. And yes, it works!
So I have a flashlight that illuminates for 15 minutes (without loss of brightness) and that loads in ... 10 seconds.
Components to achieve it are:

• A white LED (retrieved on a flashlight whose battery was empty)
• A super capacitor (10F, 2.7 V)
• A transistor
• A torus
• 1 k ohms resistance
• The wire
• A breadboard