wishing for a 5x XM-L, 2x 26650 light

I'd buy several. Seriously.

i would like to see them in D size Li-ion (36___) but it seems to be an unpopular size for some reason.

that size battery is ideal for camping in my opinion. you know you light will last forever, and its a weapon, that can explode on impact? LOL

5x XM-L? Camping eh? Who needs matches to start a fire? XD

You can get one of these:

http://www.xtarlight.com/en/05-chanpin/p-001-1.asp?styleid=67

And mod it to triple XM-L probably very easily.

I guess I'd go for a D-size light too... whatever the budget mfrs come up with. I just said 26650 because I've seen a few 26650 lights recently. I'd like to keep the weight down also, but maybe there's not much difference between 2x 32xxx and 2x 26650.

Budgeteer thanks for the idea, but that light is about double the maximum head size I'm willing to carry (WF-500 is the maximum).

About fires: maybe that's why nobody produces such a light yet. But I'm willing to settle for underdriven XM-Ls. Not TOO underdriven though.

I have cheap D cell torch bodies id really love to mod! 4D cell = 14.4V = great for 3 XM-Ls in series fully driven and able to give 1-2 hour+ output. 30 watts of power FTW!

4D lithium cobalt cells in series fills me with terror. Just make sure it can vent safely. I'd certainly not be prepared to use such a device, there's just too much energy in there.

I'd want D LiFePO4 or LiMn cells for that sort of thing. And I'd not be ecstatic about LiMn cells, if they get far enough out of balance they can still go kaboom.

OK, I've used a pair of lithium cobalt Ds in an ROP for several years now - roughly a 30W device. I do use the voltmeter a lot and those cells may be approaching the end of their useful life.

Make sure the cells are very, very well balanced and stay that way.

Do they even make non LiMN D li-ions? There's really no point in underdriving XML's. What I want to see is an XML triple, with 3 2.8 amp drivers, behind carclo lens, in a maglite 1C off of one 26650. 8.4 amp draw, shouldn't be too bad.

I don't know what the definition of "underdriving" is, but I meant "anything less than the stated maximum current specified by Cree". Therefore, if 3A is the stated max, then to me, 2.95A is underdriving, as is 0.05A. To clarify what I wrote previously then, I'd be happy with any current 2A or higher (understanding that an XP-G is an alternative at 1.5A and lower).

If I remember correctly, the lumens vs. current chart has a gentle convex curve to it, meaning that the LED is more efficient at lower currents, so running three of them at 1A gets you more output than running one at 3A. Or, running five of them at 1.8A would get you more output than running three of them at 3A.

But correct me if I'm wrong.

The WF-500 head is big enough to accommodate five XM-Ls, but I would also be interested in a smaller light with three XM-Ls, similar to the one srfreddy described.

So, how do we get the attention of Ultrafire, Yezl, Brinyte, Mr. Lite, etc, to ask them to build these things for us?

I just ran across a MicroFire K5 Tactical (now called Challenger II L2000R) which has 19 Q5 bulbs. Coincidentally, I don't have $750 to drop on this bad boy. And all we want is a puny 5 XM-L set-up.

be seen, not entirely true. the more efficient, the less heat.

heat is one form of energy, so is light. more light, less heat, but you are correct, it still requires TONS of heat sinking

4sevens has made a prototype 18 XML searchlight. It uses 32 18650's though, but it includes a charger *phew!* Now all he needs to do is size it down into useable light amounts......

I'm sure that one will fall under the "If money were no object" catagory. LOL

3-XML in a wf-500 head with 2 24-32mm diameter cells would be amazing. I can't see any budget light manufacturer doing that any time soon though.....

Yes, KD will sell you them.

http://www.kaidomain.com/ProductDetails.aspx?ProductId=2708

They are longer than a D and flat topped so you need a shorter spring and magnets to make them work in a stock Mag body.

Im currently using an old school CPU heatsink from the Pentium4 era (a fist sized block of alum) and it can manage to passively cool a sst-50 driven at 18 watts, bringing the temps up to around 20 above ambient for 30 mins of running. Thats a cool 40 degrees C in a 20 degree environment. Those are massive heatsinks, and just are not practical for use, even in a torch. The Legion (on the right) has a very substantial heatsink by normal torch standards, but when placed side by side with the CPU heatsinks, its not fair. The other torch was a discount retailer (BigW) torch that was bought for $15 or something. This is the 4AA version, I also have a long tube version (4D cell) of the same torch with interchangable parts. That torch would have a real heatsinking problem if modded to 10+ watts.

I've also got a rough plot of the measured temperature of the base of the heatsink in my torch over a medium run time. Essentially, looking at the graph, Temp is on the left axis in deg C, and time in seconds on the bottom axis. Temps are seen to rise until I turn the torhc off at 14.5 mins. Extrapolation can show that this torch will continue to rise in temperature if left alone, maybe within an hour reaching 80 degrees C, measured at the base of the heatsink (closest part to the emitter).

This is the Legion, the torch on the right. The thermocouple was placed into the last heatsink groove from the outside. Still a very respectable performance for a torch thats drawing 18 watts from 3x 18650s. Im not sure what emitter power is, but its "apparently" meant to be 90+%ish so even if 16 watts makes it to the led, and half of this is heat.

Dissipating that much heat (30-40W) in a manageable sized light is just not possible. Not with any kind of reasonable design. You'd need lots of very thin (re: fragile) fins and heatpipes to get the heat away from the slug. Look at modern/high end cpu heatsinks and you'll see whats necessary to get rid of that much heat.

EDIT: I just want to clarify by saying, that you can build a light that burns though 40 watts, but thermally its not going to get rid of enough heat to run for extended periods.

Not quite that bad - 30-40W is Pentium 3 territory and CPUs probably care more about their internal temperature than LEDs do. Modern CPUs can easily go to 150W.

Still not easy. My SST-90 light is a 35+ watt LED light and it will overheat if run continually on max for more than 30 minutes. Since the 4 Cs in it last for 20 at full output it isn't an issue for me.

We may have to start thinking about the duty cycle of lights. This is already necessary in small 10440 powered lights. The ITP A3 EOS Upgrade (What a mouthful - A3 from now on) can run on 10440s but the heat on high will rapidly become unmanageable.

You're right that a LEDs can handle higher temperatures. I was just trying to say that in order to make a light that doesn't just keep getting hotter and hotter until you can't hold it anymore, the design has to include a way to get the heat OUT of the flashlight rather than just giving it a larger reservoir to store the heat in it until the batteries die. :)

I've got a XML driven @ 3.1A in a 1x26650 light and within 10 minutes its hot enough that I can't stop thinking about how hot it is. LOL

Basically I agree with you. However you work it, 30+W lights are going to need a LOT of attention paid to getting rid of the heat.

And fans are highly undesirable. I can't see something like this being integrated into a light.

And that was the most likely looking one I came across. Heatpipes are probably going to be needed for handheld use but they are much less effective in non-stationary applications.

I do think fans are viable in larger lights though.