WIP super cheap 100w flashlight

Hi everyone
i'm trying to realize a 100w led flashlight with a very low budget, just for fun!


What i did for now is fixing one of this led http://ledtronix.trade47.com/files/2014/01/100w-led.jpg
to a cpu heatsink+fan, i added the lens (standard 44mm lens + reflector) and i connected it all to a small voltage booster board,
so i can reach the 32-36 V needed starting from a 12v battery.

Now that's the part where i need some help:

1) Is there something as cheap as a 12V 9AH lead acid battery but better (size, duration, discharge rate...etc) than that?
2) The 44mm lens with the small reflector is quite useless, i'd like to concentrate it a bit at least.
I was wondering if reflector made for a COB led would work;
i found this : http://www.dx.com/p/cob-97mm-square-hole-aluminium-alloy-reflector-for-led-lamp-387951
that seems very good, what do you think would be the result ?

If you have any advice please share them, as you can see i'm everything but expert.

No other battery will match a big lead-acid for cheap power. Any good nickel or lithium based battery will be smaller and lighter, but more expensive.

I don't know why you'd want to use a lens and a reflector, generally that's counterproductive.

You haven't said what kind of beam you are looking to achieve, but to achieve a narrow beam without lots of spill (or wasted light), you need an optic that's much larger than your light emitting surface. Because that emitter is so much bigger than the LEDs that are used in throwy flashlights, you'd need a gigantic lens or reflector. To do a good job of this, a reflector should be substantially deeper than it is wide, and a lens should be at least as wide as it's focal length, preferably wider.

If you're looking for a central hotspot with lots of spill, a reflector like the one you linked can work, though I don't know enough about that particular one to comment on how it would perform.

Generally, big LEDs like that are intended for area lighting, for the aforementioned reasons. A reflector designed for these LEDs might be expected to provide flood or narrow flood lighting with no hotspot, so I wouldn't be surprised if that's what you get out of that reflector.

Thank you for all these information!!
The power issue is now "solved" then, i don't want to spend a lot of money for a 18650 battery pack, so i'll go for a 12ah lead acid, moreover i already have a good car battery charger so it won't be a problem.

Now comes the hard part:
from what i understand i'll never have a super throw flashlight, ok, that's not a problem and it's not my purpose
But at the moment, with or without the 44mm lens (you can see it here: http://i01.i.aliimg.com/wsphoto/v1/...Fixed-bracket-For-30W-100W-High-Power-Led.jpg )
the light is almost 180° wide...
My aim is to have ... idk ... something like 90° or so, but without loosing much light, concentrating all the light from the emitter to a slightly narrower angle.

Do you think is this possible? how would you achieve this?

That reflector you linked might do that.

Imagine a black sheet of paper, with a hole in it that's the diameter of the opening of the reflector. Place it in front of the LED, right where the opening of the reflector would be, but remove the reflector. Now some light will hit the paper and be blocked, while some will shine through the hole. This is the 'spill', and it's light that would never have hit the reflector, and thus cannot be gathered into a hotspot.

Only the light that hits the paper can get reflected into a hotspot.

You can see that if the reflector is wide and shallow, most of the light just comes straight out. The longer and narrower it is, the more gets gathered by the reflector, and the narrower your spill is.

Now consider the shape of the reflector and the location of the LED within it. These will affect the size and appearance of the hotspot. It can be quite wide or fairly narrow. The relative size of the LED and the reflector dictates the minimum spot size. But you don't really care about a narrow spot, so you don't need a huge reflector.

Now consider the surface of the reflector. A smooth, uniform finish will give you the narrowest hotspot, but can create 'artifacts', which are areas of brighter and darker light within the beam, caused by the shape and surface of the LED. An 'orange peel' or OP finish is designed to break up the artifacts and make them less visible. It also widens and softens the hotspot. The faceted surface of the reflector you linked is probably designed for a similar effect, but I suspect to a lesser degree.

Thank you for explaining it in such a simple way, really appreciated by a newby
Now i got it, i should use a really deep reflector to have a really narrow spot with such a large led, cause otherwise i'll end up with a lot of spill.



Well, maybe for the low price i'll try to order the one i found on ebay, it's not perfect but it could help a bit, also only for an aesthetic reason


What about lenses instead?
As i said i have a 44mm one with his collimator, but the result is not so good...
What would happen if i put a larger lens (like 78mm or 100mm) in front of the led?
Would it help?

Sorry for being here to ask some noob questions but i need some advices

Let's assume that i'll put a reflector in front of the 100w led, for example a 100mm in diameter and 50mm in depth one.
Of course i'll have a slightly narrower light output if compared to the bare led.

Now i was thinking about this:

What would happen if i put a lens (aspherical or fresnel) that have a diameter of 100mm and a focal length of 50mm exactly in front of the reflector??
The lens should capture most of the light coming from the led and the focal length is correct, so i think that i'll end up with a focused beam, way brighter than what i have with only the reflector, am i wrong??
Which are the cons in such a method?

The light coming off the reflector is not at the focal point, so it won't get focused properly. In fact, even the light at the edge of the emitter isn't getting focused as well as what's coming from the center, where the focal point is.

DIWdiver said:

The light coming off the reflector is not at the focal point, so it won't get focused properly. In fact, even the light at the edge of the emitter isn't getting focused as well as what's coming from the center, where the focal point is.

Click to expand...

Thank you for the reply!
If i understood correctly than only a really small % of the light coming from the emitter is properly focused, and it's the light coming from the center part of it.
I'm wondering if there's some kind of way to use to lens for focusing the light with the first and re-focusing it with the second, for better throw.
I think i'll do some cheap experiments

annykizz said:

Thank you for the reply!
If i understood correctly than only a really small % of the light coming from the emitter is properly focused, and it's the light coming from the center part of it.
I'm wondering if there's some kind of way to use to lens for focusing the light with the first and re-focusing it with the second, for better throw.
I think i'll do some cheap experiments

Click to expand...

There's an old thread utilizing dual lens setup however the photos have been removed :-(
https://www.candlepowerforums.com/threads/282184
That's about the best way to gather and then project that light forward.

FRITZHID said:

There's an old thread utilizing dual lens setup however the photos have been removed :-(
https://www.candlepowerforums.com/threads/282184
That's about the best way to gather and then project that light forward.

Click to expand...

Wow that's exactly what i had in mind!!
It's funny because i feared it could be a bullshit, but it seem it's not

Thank you for the link, i can't see the pics but reading the whole thread i can see it's a project that goes way far beyond my aim (and my skills).
The case for my light will be a 4,7" pvc pipe so that's the biggest size for a lens i'm going to use.
The main problem is to calculate what would be the best size/focal length for the first lens, the one in front of the led.
I can find some 4" fresnel lens with a relatively short focal length, something like 1,6".
Do you think if could work or an aspherical would perform better?

Well, you can't see it but he used both. A close to die Aspheric-like lens to gather/focus the majority of the light then the Fresnel to collmate it into a far throwing tight beam. (And in the pix, it was crazy focused.... & focusable!)
I'm sure there's a combination of smaller lenses to achieve similar results. There's probably higher loss tho. Try looking into laser beam collimator designs. They utilize multi lens setups and would give you a starting point.

FRITZHID said:

Well, you can't see it but he used both. A close to die Aspheric-like lens to gather/focus the majority of the light then the Fresnel to collmate it into a far throwing tight beam. (And in the pix, it was crazy focused.... & focusable!)
I'm sure there's a combination of smaller lenses to achieve similar results. There's probably higher loss tho. Try looking into laser beam collimator designs. They utilize multi lens setups and would give you a starting point.

Click to expand...

Yes, i got the overall design of the project in the thread you linked, but i'm wondering about the shape of the first lens i need, because my emitter is way too big for what i'm trying to do. :laughing:

If i have to guess i'd say that, for the first lens, i need a big one with a short focal length (impossible to find), that collect most of the light coming from the big emitter and redirect it with a narrower angle through the second lens, that of course need to be as big as possible.

i looked at the laser beam collimator designs but i'm not able to get an advice from them, it's too complicated for my knowledge.