This is an example of a supercapacitor flashlight that can be charged with a standard 1A smartphone charger.
French people can find the entire description here :
Step 1: You Will Need
- micro-usb connector
- 1.1A Polyswitch
- 4.8 ohm 1 Watt resistor
- 1000 ohm, 82000 ohm, 220 ohm and 11.4 ohm 1/4 Watt resistors
- buck converter (RC Airplane Module Mini 360 DC Buck Converter Step Down)
(4.75V - 23V to 1V - 17V)
- 1N5817 diode
- Supercapacitor 30 Farads 2.7V
- TL431 (adjustable shunt regulator with 2.5V Vref)
- green LED 3mm
- boost converter (mini DC DC 0.8 - 3.3V to 3.3 V Step UP Boost converter)
- white LED 5mm (20000 mcd, 3.1 to 3.4V)
- soldering iron with solder and flux
- jumper wires
Step 2: Adjust the Buck Converter
With the micro-usb connector and a breadboard, you have to connect the buck converter, the Polyswitch, the 1N5817 diode and a 1000 ohm resistor.
You connect a voltmeter to the resistor.
Then you turn the buck converter screw to obtain 2.6V.
Step 3: Turn on a Green LED When the Supercapacitor Is Charged to 2.5V
The TL431 device is a three-terminal adjustable shunt regulator. The output voltage can be set to any value between Vref ( 2.5 V) and 36 V.
So it's easy to turn on a LED on 2.5V with a TL431...
Step 4: Breadboard and Perfboard Supercapacitor Flashlight
When the switch is engaged, the supercapacitor feeds a small boost converter which boosts the voltage to 3.3V to power a LED through a 11.4 ohm resistor.
If you need more information, you can read the original description (in french) of this supercapacitor flashlight here :