Led Flashlight with Super capacitors V2

[dinoth]

Hi guys.
I made modification on my Flashlight.
Added Joule Thief and Capacitors are in parallel now to get 2.7 V 600 Farads.
Run time is increased from 20 minutes to more than 4 hours.
Light intensity is little lower but it is worth it.
Replaced USB charging port with normal connector.
Bought on eBay Step-down Power Converter 2A.
I made a video on You Tube.
https://www.youtube.com/watch?v=lRsMs8CN5RM

[MarkE]

Nice project. 

Assuming that your JT circuit works down to around 0.8V (many do better), then you can extract: 1-0.64/7.29 = 91% of the energy in your capacitors, or about 1990 J.   A AA alkaline battery by comparison holds about 2.4Wh or ~8800J.  So if you set-up with a pair of AA batteries, you would have roughly 9X as much energy available, but of course the unit would not be rechargeable.

Now, the only question is how much of your available energy that you are converting to light after going through your JT and LEDs.  Since you have a 40 hour run time, you are pulling about 50J/hour or 13.9mW from the capacitors.  State of the art power conversion and LEDs would yield about 2.6 lumens, (about the same as one candle ) yielding about 104 lumen hours.  You are using bulb style LEDs and JTs are notoriously inefficient, so you are probably getting more like about 0.35 - 0.50 lumens, which translates to around 14 - 20 lumen hours per charge.   If you change out the JT for a current controlled LED driver then you should be able to about double or triple your lumen hour product.  If you get some of the super efficient LEDs that are around then you can bring your lumen hour product up again by another factor of 3X or so.

[dinoth]

Thanks. My JT runs to about 0.6 volts but I would never discharge caps so much, really no need.
And run time of 4 hours is more than enough.
My goal first was to replace lead acid battery and now run time of 4 hours, is more than enough.
That is basically what I need.
Maybe in the future I will modify it further to increase lumens and run time.

[sm0ky2]

nice work

my brother builds JT-Lighting in his house, with superbright LEDs that use very little power.

in all sorts of containers, altoids cans, little plastic things, old flashlights, etc.

he  doesn't need to turn on any normal lights in his house,
and these things run for a month or two on random "dead battery" out of the battery box
much longer for him, since he switches them off when he leaves a room.

[MarkE]

Thanks. My JT runs to about 0.6 volts but I would never discharge caps so much, really no need.
And run time of 4 hours is more than enough.
My goal first was to replace lead acid battery and now run time of 4 hours, is more than enough.
That is basically what I need.
Maybe in the future I will modify it further to increase lumens and run time.

0.8V is typical for a lot of JTs.  The lower the better but compared to 0.8V 0.6V only improves the harvestable percentage energy from the capacitors by about 4%.  It is not very significant.