Intro: Supercapacitor Flashlight
Using a 5 watt MR16 led light, this (50 watt equivalent) flashlight (weighs less than one pound) really puts light in dark places. The capacitors can be recharged hundreds of thousands of times--so there's no worry about wearing them out.
Using a 5 watt MR16 bulb, the light will shine for about six minutes--it can be recharged in 90 seconds with a 5 amp power supply. A 2 watt MR16 would give about 15 minutes of light (and could be recharged in 45 seconds with a 10 amp supply).
Don't be afraid to work with these capacitors--they store less energy than a AAA battery, but they can receive and discharge current quickly--generate some heat on a wire if the wire shorts the terminals (for comparison, an AA battery powered soldering iron can reach a temperature of one thousand degrees in seven seconds).
(2) 350 farad 2.7 volt capacitors Mouser Electronics These cost about $12.00 each at this supplier
(1) 5 watt MR16 bulb Amazon
(1) Boost Converter amazon
(1) Power jack socket Amazon
(1) Power plug to fit jack socket
(1) MR16 light socket
(1) Power supply that can provide constant current up to 5 amps Amazon
(1) On/Off switch
(1) 5 amp fuse and socket
Misc: solder, heat shrink tubing, wire, M3 screws
Print 3d parts
Insert the MR16 socket into the top piece. Secure using M3 screws.
Insert bulb into socket.
Drill hole in back side of switch piece (yes, I should have designed it into the 3d file; but I didn't know that at the time).
Solder wires to switch and secure to switch holder.
Solder wires to jack. It is advisable to have a plug in the jack when soldering--otherwise, the center pin may get too hot and move around off center.
Adjust the DC converter to 12 volts output (using the small screw on the board).
Solder wires to the DC converter. Connect the top of the light and the switch pieces using a soldering iron to melt them together.
Solder remaining wires to the converter, then secure the converter to the upper capacitor holder using an M3 x 8 machine screw.
Solder the wires to the supercapacitors. Use heat shrink tubing when wire connections could move around. Do not allow the supercapacitors to touch each other (some of the older Maxwell supercaps were not insulated on the bottom).
Attach a cable from the jack to the power supply. Set the power supply at 5.4 volts and 5 amps. The supply will limit itself to 5 amps as the voltage rises--you don't want to exceed 5.4 volts on the series connected capacitors.
That being said, I set the voltage at 5.8 volts and watch for the charging current to dip below 1 amp (this gives me a faster charge).
Turn it on. It is really bright and lightweight!