I just switched to a 330 uf 100v cap.  The LED is way brighter - so bright I can't stare at it without concern of eye damage or at least seeing spots    The battery voltage started out lower with this cap.  It was at 16.40 in the first few seconds after hooking it up and I could see it rising right away.  I believe after a minute or two the LED is dimming some but the voltage has come all the way up to 17.25 volts.  Got to put it on the scope to see what it looks like. 
   This opens up lots of ideas to be tried.  Thanks ibp for showing us this interesting effect.

my 2 cents

hope this helps

http://www.youtube.com/watch?v=ZNbZNlX4c94

good night at all

laurent

Just a couple more notes on observations with the high power LED.  Battery voltage topped out at 17.86 after maybe 20 minutes running.  When I disconnected the setup it returned to 18.01 volts.  The LED was dimmer near the end so I decided to check the alligator clip on the top of the Cap.  It was held  down with electrical tape.  I removed the tape and noted an interesting effect.  When the clip was in good contact with the top the LED was fairly dim now.  But when I pushed down on the clip the harder I pushed the brighter it got.  Both the aluminum on top of the Cap and the clip were clean.  So good contact was made even with light pressure but additional pressure seemed to provide a linear increase in brightness.  i.e. more pressure=brighter over quite a range  ??

Quote from: e2matrix on November 10, 2010, 07:11:44 PM
Just a couple more notes on observations with the high power LED.  Battery voltage topped out at 17.86 after maybe 20 minutes running.  When I disconnected the setup it returned to 18.01 volts.  The LED was dimmer near the end so I decided to check the alligator clip on the top of the Cap.  It was held  down with electrical tape.  I removed the tape and noted an interesting effect.  When the clip was in good contact with the top the LED was fairly dim now.  But when I pushed down on the clip the harder I pushed the brighter it got.  Both the aluminum on top of the Cap and the clip were clean.  So good contact was made even with light pressure but additional pressure seemed to provide a linear increase in brightness.  i.e. more pressure=brighter over quite a range  ??

It's true what your comets, I have also tried the following:

Charge the capacitor, and give him a very light touch to the top with the pin on the LED, there is a very small flash, then connect the LED to the negative of the capacitor, and gives you that just as there is always a very very big flash. ..

Quote from: Trastos on November 10, 2010, 07:53:32 PM
It's true what your comets, I have also tried the following:

Charge the capacitor, and give him a very light touch to the top with the pin on the LED, there is a very small flash, then connect the LED to the negative of the capacitor, and gives you that just as there is always a very very big flash. ..

are you talking about this?
http://www.youtube.com/watch?v=KQJZs6tlj_Y