Liquid cooled XM-L Eveready 2D sleeper

How about shortening the light, running it from a single AA in a D-to-AA adapter, with a ~350mA boost driver, and cooling provided by quad 225 watt peltiers powered by a marine diesel generator! YEAH!

Isopropyl alcohol flames are easy to see.

That was 70% alcohol, try the good stuff…

Watch the entire video.

Oh, and let’s not forget that 90% isopropyl is 10% water… which will electrolyze into hydrogen and oxygen. This light has some great hillbilly entertainment potential… J)

whats wrong with an alcohol, hydrogen and oxygen cocktail in an electronic enclosure? might spark a little interest

Unless he moves it hopefully it won’t blow up.

And another note, this isn’t really liquid cooling. Liquid cooling requires transferring the heat to the liquid, then cooling the liquid and finally bringing it back to the heat source to bring more heat away.

This has no way of bringing heat away from the liquid. So if it doesn’t blow, it’ll work for a few minutes, then it’ll be the same as any other light.

this may have some potential since plastic can have good emissivity though a safer liquid should be used but I am very interested in its potential and I hope if fritz tries it (safely of course) he posts some measurements

Oh, I notice that you too are talking about “ignition”. No, an led won’t work at ignition temperatures. No led can ignite ordinary flammable liquids, unless the light is strongly focused with a lens or concave mirror to a tiny spot much smaller than the led. It would burn out first. You are thinking of incandescent lights.

That was the first thing I thought of, though it is interesting that people use it in small computers. Then someone on the Angel Head thread found an ad. for a silicone oil filled light bulb. Alcohol is more different from silicone and it will cool better. Boiling will be an advantage if it does it at all in my 2D light, though it might be a problem with a more powerful power source or in a very hot place. My inspiration is the Cray II that I saw in an aquarium full of freon. It had streams of tiny bubbles coming up from the components.

I have been playing with flammable liquids since I was about 8 and know all these things. There is no source of ignition and the amount of alcohol I am using is little hazard. I may avoid leaving it alone or in the hands of inexperienced people, but I have seen candles in wooden candlesticks that are far more dangerous. The alcohol probably won’t light the plastic, though I wouldn’t bet on it. What I am more confident about is that neither a three volt short circuit with copper wires nor an led of any sort can ignite any variety of alcohol.
I am not a safety expert nor am I willing to listen to one, so I don’t see anything to be gained by continuing this discussion.

like your thinking. be sure to update us on this experiment

I had similiar concerns when I first saw that you were using alcohol as the cooling agent. I think as long as you take the proper precautions, nothing else needs to be said.

Do you have a way of measuring the temperature to the LED before and after? Curious to see if it actually makes a material difference. In theory, you would think that the alcohol would help absorb the initial heat from the heatsink but after the aluminum and alcohol is heated up to temperature, there would be no additional benefit gained. Interesting experiment neverless.

Here's another idea you may like to try out if your original experiment doesn pan out.

Using compressed air (CO2) to cool/reduce heat to the heatsink.

In a past project (unfinished) I've attempted to attach a small replaceable CO2 cartridge like ones they use in air guns to a maglite host. You would push the bottom of the cartridge to release the air. A small tube (1mm inside dia.) was attached from the cartridge to the heatsink via hole through the flashligh body. In theory it works. In the test trials, it works. The problem was that the contraption was a little to big and combersome but it works and works very well per the IR thermometer. Also the thought of spending hours designing a trigger that would look 'cool' put an end to that project.

It's currently sitting in the "to-do-on-a-rainy-Vancouver-day" project bin. What can I say the power of 'laziness' was overwhelming!

Again good luck on the experiment and hope to see some good results.

The point is that most liquids and especially alcohols expand on heating, so the heat is transferred to the mirror and especially to the large thin front window (lens), from which convection of the air takes it away. If it gets very hot anyway, which may take more than 2 D cells, I expect to see a stream of tiny bubbles, like I did when I saw a Cray II running.

Only by looking, probably with a camera, for bubbles, and by feeling if the window gets warm. I could feel or measure the pill by running it without the case, but I don’t see that as much of a question. Until there is a metal conduction path to compete with, the alcohol will do most of the cooling.


Have you run a XML from two D cells yet and checked out what happens? I can tell you, not much at all. Even if you resort to a boost driver you'll find there aren't any boost drivers anywhere on the planet that will run a XML hard enough from 2 Ds to need any kind of special cooling at all.

How about what happens when really pushing one to 18-20 watts, double the rated power, using another power source? Do you have an idea of what actually happens, how much heat it makes, what kind of cooling is needed to keep the light output from sagging?

In short, have you played with this hardware enough to get a good understanding of what you're working with? The combination of 2 Ds, a single XML, and liquid cooling tells me you don't, not yet anyway.

I measured the current passed by 70% and found it small, as I said in the angle head thread. That means the hydrogen and copper oxide produced is also small. Three volts is around the minimum for hydrolysis of water. The driver probably increases it but not much.

Yes, I will have to work up to higher power before it can really become interesting. So far I have only tried it with the two acid dry cells that came with the super budget lights. I will be back to continue in a couple of weeks. I think I saw on some thread lithiums of around D size. I am hoping that the 2 D alkalines will give enough power that it would overheat without the liquid in this almost all plastic light, once the pill has a chance to heat up. Another thing I might try is turning the led backward with a more complete reflector. With the led moved away from the pill, it will need the liquid even at very low power.
As far as it being a useful light, it now has a very useful spill, at least compared to other lights with acid D cells, but not a lot of throw. So it is also a possible vehicle for adding a secondary reflector as well as for reversing the emitter. The long focal length reflector gives a small spot, but it is yellow and not very bright because the reflector is shallow and doesn’t catch much light, in the present configuration. It is already bright enough to surprise people that think it is a stock Eveready!

Three alkaline D cells direct drive to a XML will only run at about 1.8A, and in a stock 3D Maglite that's low enough that the LED will do just fine even in a bulb replacement format, installed in the stock plastic focus-able bulb tower, with no additional heatsinking. Just floating there atop the Mag's great sea of plastic. Three D cell NiMh are a different story... after about one minute run time wispy trails of smoke will start rising from the LED/bulb holder, that setup runs about 2.4 amps. So around 1.5-1.8A no substantial heatsinking is needed at all. XML/XML2 doesn't get impressively bright until you get up around 3 amps.

The low voltage from only 2 cells will greatly limit the current to the LED irrespective of the theoretical current the cells are capable of delivering, such that you can hold the bare LED in your bare hand and it will barely feel above room temp. I haven't bothered measuring a 2 cell current draw as it's too low to be useful, and I know what it does with 3 cells, but I would guess the 2 cell would run at less than 350-400mA.