P60 XML - which one to buy?

About the length of time the battery charge lasted - 40 minutes. Less if I wasn't using my hand as a heatsink. If the snow stays away I'll find out next week as I hope to be off into the wilds with the assistant to annoy the local wildlife and do some longer-range beamshots. About 1km from here.

Last time I went there was great weather every day, but as soon as it got dark, it rained every time.

I honestly don't know if that would be better or worse. You would have to be careful that the wire didn't go to places it shouldn't but a blob of solder would hold it in place. It might take a long time to wind it neatly and tightly - you would probably want to use very fine wire so you could stuff as much of it into the gap as possible. If you do try this, I would love to hear how it worked.

Make sure it is tinned or plain copper wire, not the enamelled stuff used for winding transformers and inductors - the enamel would be a very poor conductor of heat.

What we are trying to do is to replace any air gap with metal so a tightly wound dropin ought to conduct heat away from the dropin very well. Once it is wound, dipping it in solder (After masking off everything you didn't want soldered) to keep the wire in place and fill as many remaining air gaps as possible ought to give excellent results.

What does that mean? The driver would shut off the LED if it got too hot?

Oh, you just made me want to go back to Scotland... Been there only for six weeks, but it was splendid and I really want to come back to all the wonders of this land that I've seen (and tasted! :) ) and to fill in what I've missed (the Outer Hebrides, Shetland, and many isolated places I could not get to with public transportation). I really enjoyed the nature, castles, people, highland games and the taste of whisky, and I even learned to play pool (by an englishman at my hostel). Hmm... must go back there. :)

No, I'd not be very happy to let pretty much any light run a battery empty on full power without some sort of heatsinking. Your hand is good for this as your blood will take the heat around your body. Quite a lot of lights can become painful to touch of you don't let them lose heat through your hand. The Ultrafire C3 SS will become painful to hold in about three minutes on high with a 14500.

40 minutes is about as long as a typical 18650 will run one of these on high. Most drivers won't shut of on excess heat - the only ones I can think of that do are the Ra lights ones but those aren't remotely close to budget lights. Some of the more powerful Fenixes may do.

I want to do a runtime on these anyway so will charge up a cell and keep an eye on temperatures while I do so. Unfortunately I can't log temperature at the same time as output but I have some ideas for that which I hope to have time to play with next week. What I really want is a thermal imaging camera, which my brother's company would be happy to sell me - at the price of a good new car.

4530 lux at switch-on.

Temperature of head at switch-on 18.7C. This is the foil wrapping as seen in the pictures above.

At 1 minute 24.9C

3 minutes 32C - output down to 3800lux.

5:30 39.8oC

Here is the setup.

The meter on top of the lightbox is measuring microamps from the solar cell at the far end of the lightbox that I use for output and runtime measurements - it is connected to the PC you can see on the far left of the picture. The meter on the right measures lightbox lux which I divide by 892 and multiply by 160 to arrive at "my lumens".

The meter on the left is measuring temperature. There is a small thermocouple taped to the head. In theory I ought to be able to attach both meters and log data - in practice the £W@$%%$^& Windows drivers only see one meter at a time and it appears to be completely random which one.

10 minutes 50oC 3560 lux

The foil is working. Even the tailcap is getting hot. I will stop at 60oC as the internals will be getting a lot hotter. Normally I would point a large fan at the light while doing runtimes on high.

14 minutes 54oC 3500 lux

I think most digital cameras can pick up infrared (maybe you'll need to take off the internal IR filter), so you could make a "poor man's thermal imaging camera" by using a filter that passes only IR, and use time-lapse photography or even record a video of the flashlight.

You can perhaps get the temperature values by using fixed exposure settings and calibrating the gray level with a known temperature heat source and a non-contact thermometer.

But that's a lot of work and I have no idea how accurate such a device can be...

17 minutes 58oC 3420 lux

58oC is painful to hold for most people - if it is in your hand it will not get quite so hot and it probably hasn't reached LED damaging temperatures. You will know when the driver hits 160oC - the solder will melt and it will fail.

19 minutes 59.5oC 3380 lux

20 minutes 60oC 3360 lux

I switched it off at 20 minutes. In your hand it might be good for 25 minutes till it became uncomfortable to hold.

I will let the light cool, let the battery cool, recharge it and remeasure the output.

The test was done in an old-style Ultrafire WF-504B which is a clone of the Solarforce L2, but is lighter. The Solarforce body might give slightly better thermal results as it has more mass.

Hi folks. How do you see this idea?

P60 + XML T6 led. Driver = kaidomain 8x7135 (2,8Amps)

Also, cover the dropin with aluminium foil.

If I am not wrong, on HIGH mode it feeds to led 2,8A (800 lumens). On MED 1A (300-350 lumens)

So, a solution can be, keep the light always on MED (300-350 lumens) and use HIGH (800 lum) for short periods? 300-350 lumens is a respectable amount of lumens.

What do you think?

Run on HIGH lets say, 10 minutes, and switch to MED for 5 minutes to cool...

Agreed entirely.

From my measurements it is OK for 20 minutes on high. Which is probably around half the charge of the cell anyway.

Well, the final question. With the trick of the aluminum foil....will be enough for cooling? will the led fail? or decrease efficiency?

Once the light and cell have cooled off I will charge the cell then rerun the tests to see what happens. I don't have an answer just yet, but i hope to have one in an hour or two.

Time for some output measurements.

I have no idea what to expect. This time I'll keep it in my hands and see how long I can stand it for. My hands are more heatproof than most people's.

i thought the charger had turned finished charging the cell - it hadn't. Not even close.

I need to sleep now so results tomorrow.

Good luck!

Very nice test you are doing, if I'm not wrong probably the temperature into the body is going to a dangerously level for the cells. Somewhere I read this maximum allowable is around 60 C, also the anodized finish is a thermal isolator therefore the body is some degrees hotter than what the thermocouple read...the usual solder 60/40 with lead melt at 183C...

Btw how good are your cells Don? I don't get such drastic output drop over time as you do. Using the seraph clone host or fake solarforce doesen't matter much within margin of error. Manafont 3 mode no strobe dropin.

Yes - the battery was too hot for safety. This time I will measure its temperature

4740 lux at switch-on ambient temperature 12oC

2 minutes 3860 lux temp 20.6oC

3 minutes 3830 lux 25.1oC

4 minutes 3700 lux 25.5oC

6 minutes 3770 lux 29.5oC

7 minutes 3730 lux 32oC

9 minutes 3660 lux 32.7oC

10 minutes 3710 lux 33.4oC

15 minutes 3770 lux 37.2oC

19 minutes 3690 lux 39.1oC Battery temperature 38.9oC

The whole light was warm at that point, and the head felt hotter than the thermocouple was reporting - but that may be because of the 12oC ambient temperature. Indoors.

It's not the cells , it's the heat which cause the sag perfectly accord to the datasheet data.

9 or 10W is a lot of power , there are solderings iron working at that...

To give an idea this heat sink weight 180 grs 10 x 5 x 4 cm solid aluminium ...three Osram warm in series with a current of 900 ma 10,35V =9 W , the emitters perfectly attached , in a flaslight you can't reach that good heatsink however after 15 minutes of use you barely can touch it...

Also I mod one RC-G2 XM-L at 2.05 A , the 14500 flames give steady 2A even almost depleted at 3,7 V...that is around 6.5 W which the little thing can cope but as the heat increase the output decrease , if off the start numbers are reached again when all the thing is cold...you can predict the output touching the body at any given time...mean, you get 600 at cold , 550 at warm , 500 at hot...

I notice on the data sheet for the XM-L it say "Maximum junction temperature: 150°C". Is that the internal teperature they expect it to fail completely at?

Any idea what the maximum safe temperature to run them at is without overly shortening it's life?