Monster 100W LED Flashlight for Under $10!

What would you do if you came across a 100W, 7500 lumen LED diode for under $10? Probably something like this.

It’s actually quite amazing how cheap LEDs are getting. [Julian Ilett] found this 2″ x 2″ LED on eBay for only £4.79 (<$10 USD). It’s rated for 32-34V with a current draw of 3000mA, which works out to about 100W. Its brightness? 7500 lumens. That’s brighter than most home theater setups.

At that price, [Julian] had to try playing with one. The problem with these higher power LEDs is that they typically need a rather expensive LED driver, due to the less common voltages they operate at — and of course, the concern of over-driving them and burning them out. Not interested in finding a suitable driver, [Julian] decided to try something a bit less conventional — wiring a pair of 18V drill batteries in series.

Unfortunately, fully charged drill batteries tend to hover around 20V, not 18V, which when doubled is quite a bit over the recommended voltage range for the LED. The good news is that since the LED draws so much current, there’s a good chance the voltage will drop right down to the “sweet spot” for the LED. So like any good hacker, [Julian] decides to throw caution to the wind and just try it.

As luck would have it, it worked! He darn near fried his camera sensor looking at it though! Satisfied with his test he’s gone on to make the world’s cheapest — and perhaps ugliest — 100W LED flashlight.

And upgraded it since.

And if you don’t need that much brightness, you could always recycle your lithium batteries into some awesome PVC flashlights!

[via Hacked Gadgets]

63 thoughts on “Monster 100W LED Flashlight for Under $10!

    1. Probably. The main problem with projectormods is to channel the brunt of those lumen through the optics. Those optics are usually rather tiny (that’s why the reflector of a regular projection bulb has a certain shape: to get as much light bundled as possible), and you might be firing a whole lot of light into nowhere. :)

      1. What about a LumenLab projector? I have a V2 projector from them, and my current mod has replaced the electric ballast with a solid ballast (which sits outside of the projector with a large capacitor… I would love to find a way to fit a LED replacement since the current bulb in there needs to be pre-warmed before it will fire. Kind of a pain in the butt..

        1. Did you post about that anywhere?

          Also interested in LumenLab bulb mods, got one sitting idle. Theoretically uses a commodity HID bulb, but it’s built into funky proprietary base.

    2. The only real problem with using this to replace a projector bulb is that the color needs to be pure white. An RGB version of this with a proper driver and color sensor might do it.

      1. RGB produces a poor white, even if you monitored the colour output, the dies are still offset which causes uneven output in a spacial sense (and the larger the led form the more dies so bigger the problem).

        That’s why you can get RGBW leds.

      2. A better idea would be to use a filter to adjust the output to 6500k, a cheap plastic one might suffice even.

        This LED has enough output to afford the use of glass/plastic filters. Only problem I see is that I’m not sure how easy would be to measure the exact output of the LED to try to match it to the best filter possible.

        1. LEDs are monocromatic light sources. You can’t filter one to add wavelenghts that aren’t there.

          If you use this kind of high output “white” LED to power a projector, the output is heavily tinted to blue or possibly magenta, because they only include blue, yellow and red LED dies, and there’s barely any green wavelenghts.

          It tricks the eye into believing the light is white, but it isn’t.

          1. You don’t filter to add wavelengths, you filter to substract them. If the colour is 3000k it means it has a bit more red in it than what you would want it to, so a filter is used to block some of that wavelength, dimming the output but also correcting it.


            That is just the 3rd result of a google search for “filter led light”, if you want more information about it it’s not hard to find.

          2. That yellow is a phosphor though isn’t it? We’re not looking at LED output, we’re looking at special recipe phosphor emissions excited by backside LED.

    3. I have a free projection tv, 100W LED, and power supply, I got to try just that, so far its on my fail pile, cant get the light to channel, I’m not good enough at optics, still trying tho. maybe one day there will be an optics HAD post and I’ll learn what I neeed.

    4. I’m in the middle of replacing the bulb on an 8mm projector with a 100 watt LED. So far, from my initial testing, it’s brighter than the original 8V 50 watt bulb, and it doesn’t burn the film if left on a single frame.

    5. My projector is a Toshiba TLP771, 1024/768. It’s the one with the overhead projector camera. Original price $10,000. I picked it up for $10.

      The bulb in it still works but I’ve no idea how much life it has left, nor can I find the information on how to get it to show how many hours are on the bulb or how to reset the hours when changing the bulb.

      Of course to mod it with an LED module like this would require disabling the good bulb detection and the high voltage output – and finding somewhere in the circuitry to tap in to power the LED module. Fortunately it already has a good airflow through the bulb section so cooling the LED wouldn’t be a problem, especially since it wouldn’t need anywhere near 7500 lumens to be comparable to the original 1800. I’d expect too much more than stock could wash out the image.

      Another project I’ve been wanting to do, but haven’t found the software to use, is a remote control program for Windows for the projector. The command codes for the serial port are all in the projector manual, much like how it used to be for dot matrix printers.

    6. Ok, I have chinese 100W white plateled (driven around 70W as that has pretty good heat/light ratio).

      I tested it with 3LCD projector with and without additional (not too good, cant focus it into single beam) optics.
      – Light output is best when the plate is against the aparture for lamp without optics (mine was about the same size as the led and the aparture has twin lenses for the original bulb in it).
      – Light output might be good for darkened room, with original bulb just curtains closed is enough.
      – Colors are similar and projectors have pretty good adjustment for that so not problem.
      – The led outputs less light (I started the projector lamp outside the projector and it was painful being around when it heated up)

      It all comes down to focusing the light to single beam. I only had lenses from a broken cameralens and automotive projector headlamp.

      If anyone has ideas about proper lenses that could do the job, please tell.
      Lenses under 7cm diameter fit inside the original compartment and the beam should be 2 to 3cm wide (same as led die).

  1. LEDs are current driven, right? The voltage isn’t the problem. He needs a power resistor in there to limit the current. That’s as much of a hack as this. A proper driver of course is a constant current driver with PWM.

    1. The point the author was making was that the maximum discharge current of those nicd batteries is less than the rating of the LED. No resistor needed for that specific combination of LED and battery.

      1. When LED heat up their forward voltage drop so that if the power input is a constant voltage the current will increase and it create an avalanche effect. If one want to garanty LED lifetime it needs a proper current regulator not a “well the battery internal resistance limit the current”.

        1. “LED without current limitting resistor

          First of all, why would you want to get rid of the resistor? There are two reasons. First is, it wastes energy. It converts electrical energy into heat. But we want to light up an LED. Not good. Second is, you can reduce the number of components. The circuit gets cheaper, because we saved a resistor and maybe space on a PCB.

          There are two ways to bypass the resistor. One way is to lower the input voltage. If you are able to run your complete circuit with the same voltage as forward voltage of the LED, perfect. No resistor needed.”

          1. I didn’t mention limiting resistor. This kind of current limiting is only good for 20mA indicator LED. Lighting LED use switching control current limiters a lot more efficent. LEDs, like laser diode, are current control device.

  2. You can get complete boost converter boards capable of driving this led for cheap, then you could use either a car/motorcycle battery, or a couple of chunky li-ion cells in series.
    Although those boost converters are voltage regulated and not current regulated, so it might be necessary to put a low-resistance high-wattage resistor (1 Ohm 10 Watt, OR 250 miliOhm 5 Watt) in series with the LED as a safety precaution when using it with such boost converter.
    Ebay link (example only):

    Although there’s also dedicated driver boards for such 100watt available, but those are AC only and also quite expensive.

    1. It appears he did acquire just such a driver board at some point: he’s using one to power this beast from what looks like a car battery in the second embedded video.

      1. It is a switchmode converter, so looks can be deceiving in comparison to a linear regulator.
        I have a somewhat similar regulator module which is being used for charging my laptop in my car and it does the job great.
        Only thing I’d be truly concerned about is the quality and life expectancy of the electrolytic capacitors.

    1. 100 watts, it’s the same as a 100 watt light bulb, but without the surface area to attenuate it and no glass, which can handle the heat, there’s a fair amount of plastic in there, 100 watts would crisp that in no time.

          1. That’s incorrect, you contradicted yourself in just those 3 lines. Efficiency is determined by the % of energy emitted as light compared to the total energy input. So using your numbers:

            Light bulb = 2 / 100 = 2% efficiency
            LED = 15 / 100 = 15% efficiency

            Therefore the lightbulb is not much more efficient, the LED is

          2. ^ I’m pretty sure by saying “however:” he was referring to the fact that even though an LED is about 8 times as efficient as a light bulb it still outputs nearly the same amount of heat per watt.

          3. It’s pretty scary to have 15 watts of light in such a small area, especially as there is not much IR in it. It feels like “cold light”, unlike a light bulb or halogen light. But it is still enough energy to burn e.g. fabric placed in front of the led, and surely also your eyes if you look from a close distance.

            I managed to burn a hole in my black chair by accident with just a 30 watt led.

          4. They recently discovered some fundamental elusive stuff about why LED have the loss that they have at higher output, so that means that soon MUCH more efficient LED’s should be hitting the market. Although I’m not sure how long before they get to become 5 quid for 100W though.

          5. ” ~400lm/W would be 100% efficient for white light.”

            Only assuming continuous spectrum, which the LEDs don’t have. Lumens are not a measure of real power, but percieved brightness. The same amount of watts generates a lot more lumens if you drop out the wavelenghts that the eye is less sensitive to.

            That unfortunately makes the light quality rather crappy. Blue-yellow light is still seen as “white” but all colors seen under that light are distorted.

        1. It’s still going to generate (almost) 100W of heat which will need to be dissipated. LEDs aren’t even close to being 100% efficient (yet), so while a small part of the energy you put into the chip will be emitted as light, the mayor part will still be heat.

          1. Lumens are not necessarily the best unit of measure for LED. Radiance can be a useful conversion for comparison.

            Radiance Luminance
            1 W @ 555 nm (Yellow-green) = 683 lm
            1 W @ 470 nm (Blue) = 62 lm
            1 W @ 660 nm (Red) = 42 lm

    2. Hrmm. Driving these high power LED’s at or close to it’s forward voltage makes them go hot. They typically have 100 1watt LED modules in there so there is bound to be heat.

      Driving an LED close to it’s limit diminishes it’s efficiency (the amount of photons you get does not scale parallel with the amount of amps you give.). All those lost amps has to go somewhere.

      These COB style LED’s can get incredibly hot. They will most definitely self-destruct within a minute if there is no heatsink present. That bent piece of Aluminium is IMHO not good enough. I have bolted my 50w modules to old stock Intel CPU heatsinks+fans. They still get quite toasty!

    1. There is a guy who posted a series of videos about doing just that. He made 5 water cooled plates (machined aluminum) populated with 10 pieces of 100W LED modules. Driving them all gave, if I remember correctly something like 150000 lux in 1,5m distance. Sun on a bright day at noon is around 100000 lux.
      He did this for high speed photography.

    1. As I said above, they recently found out why they were limited to how efficient they can make them and due to that discovery it’s likely you will get hugely more efficient LED not too long from now, but the research is only a few months old so it takes time to get that into a production model and on the market. But with the interest now in replacing all common lighting including the ones in homes it means there is a huge market and interest, so I am convince they will hurry it up.

  3. I bought some Bridgelux 130W COB LED modules, one 2700K warm white and one 5000K cold white, they produce an insane amount of light.

    Too much for most domestic lighting, but i bought them for filming (warm) and construction (cold).

    1. The cooling problem for silicon chips is the same, whether you have one semiconductor junction or 2.5 billion of them. How far do they get with passive cooling of processors and video cards? There is your answer.

    2. A very big CPU cooler with 6 heatpipes but without the fan gave me >90°C with a 50W LED. A little better when the fins are vertical a little worse when they are horizontal. Running the fan with reduced voltage (~7V) dropped the temp to 60 or 70°C, what I consider acceptable and is barely audible.

  4. Holy crap, I didn’t know LED’s got that big. I am on my second second-hand projector, the old one was 800×600 resolution and this one is 1280 x 720 which is good enough for me, it has 800 hours left on the bulb, I’m totally going to try using one of these to replace it, I’m thinking there should be room enough for a chunk of aluminum to make the headsink, I just need to see how much power the projector bulb gets, this could save me spending $80 and up on a second hand projector every once and a while, that would be epic, plus I bet the head production would go down.

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