Not all P60 hosts are equal

I have an old Huntlight FT-01PJ I've been using as a P60 dropin host. But in tests with several different dropins as well as the original light engine, the light output always shows a considerable drop over the first few minutes (see the black trace below). The shape of the output curve is a familiar one which I've learned to associate with poor thermal contact from the LED to the flashlight -- the light output drops as the LED heats up. Regulators which are sensitive to battery voltage usually have a different shape, and all the dropins I tried had essentially the same shape.

On investigation, I saw that the only point of contact between the dropin and the flashlight body was a narrow band around the top of the reflector. The main body of the dropin didn't make contact since the flashlight body inner diameter is much greater -- by about 0.070".

I finally broke down and got a Surefire P6L and found that its inner diameter made a fairly snug fit with the body of the dropin, resulting in better thermal contact. Sure enough, the characteristic light output drop was greatly improved. The plot below shows the same Cree R2 dropin in the two different lights. A fan was blowing on the light during both tests.

I suspect that a little thermal compound around the outside of the dropin body might decrease the drop a bit more, although most of the remaining drop is likely due to thermal resistance between the LED itself and the dropin body.

c_c

Good detective work! Really shows the importance of a good thermal path.

Very nice!! thanks for sharing.
You are correct. Gene Malkoff wouldn't patent his M60, with an emphasis on thermal design for no reason. Thermal conduction is a very important design factor for any high output LED light.

I have always believed that the best drop-ins / hosts do not rely on large springs to conduct heat from the pill to the light body.

Can you try foil wrapping the module, so that its SNUG in the 6P and running your experiment again? I use reynolds heavy duty aluminum foil, fold it over and cut it into a ~1/2" strip. Wrap it around the aluminum cylinder body of the module and stuff it firmly into the 6P. Theoretically the tighter the fit the better the thermal conduction, but not to tight... the bezel should still be able to close down.

As mentioned before copper tape is also very good. It still takes 3-5 minutes before head warms with 1.2A 3SD module. Pill is a lot cooler.

Winx said:

As mentioned before copper tape is also very good. It still takes 3-5 minutes before head warms with 1.2A 3SD module. Pill is a lot cooler.

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Love the copper tape idea. Thanks.

You're welcome. I just searched ebay.com and didn't find anyone selling cheap. I bought mine from .co.uk:

http://stores.ebay.co.uk/stevent1358

6mm x 4 meters, £1 for tape and £1 for postage to almost all counties.

I found that thermal compound made no noticeable difference with the P6L host. I think the fit is tight enough that the expansion of the dropin from the heat makes a snug enough fit for good enough thermal contact even without the compound. The surface area is large enough that the thermal resistance doesn't have to be exceptionally low. So I doubt that tape would improve the P6L significantly. It looks like the remaining LED heating is due to thermal resistance elsewhere. Of course, if I manage to significantly improve the thermal conductivity in other places, the conductivity between the dropin and flashlight body might get to be a significant player again.

The FT01PJ is another story, though. The gap is around 0.035", so it'd take a lot of turns of tape, and more yet of aluminum foil. I scrounged through my junk box looking for a scrap of sheet aluminum of about the right thickness that I could wrap around the dropin, but didn't come across any. I'll see if I can find something along that line.

What I'm curious about is whether some of the other lights claiming to be a suitable host for the P60 have a large inner diameter and therefore poor thermal contact like the FT01PJ.

c_c

sims2k said:

Love the copper tape idea. Thanks.

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Great idea, I still have a large roll left over from lead lighting I did years ago. :thumbsup:
Check you local lead lighting supply.

Curious_character said:

The FT01PJ is another story, though. The gap is around 0.035", so it'd take a lot of turns of tape, and more yet of aluminum foil. I scrounged through my junk box looking for a scrap of sheet aluminum of about the right thickness that I could wrap around the dropin, but didn't come across any. I'll see if I can find something along that line.

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I'm sure I've seen aluminium flashing that may be suitable.

Norm

We use aluminum foil tape for roofs sometimes called roof flashing tape (Sello brand from New Zealand). It's as wide as duct tape but made of aluminum. Just cut to about 7 inches and about the same width as the flat portion of the R2 drop in reflector. Peel off tape backing and stick aluminum foil around the reflector until it's snug inside the flashlight.

It really transfers a lot of heat from the drop in reflector to my C1's bezel, right up to the tailcap switch!

That copper tape idea is really obvious, but I would have never thought about it without this thread! Top tip!
Forums at its best

For north americans, you can find aluminum tape at homedepot. As a previous poster already said, it's wide like duct tape. It's purpose is to be used on metal ductwork while the product that we normally call duct tape should never be used on ducts.

I think the tips in this thread will allow me to confidently run P60 modules in my WE M90. I was a bit worried about enough thermal conductivity before, but with the tweaks suggested here it should be fine with an XR-E module. Not sure it'd be good enough for a P60 MC-E. I can get an MC-E module for it, but haven't found out what tint it is.

What kind of effect does the adhesive on the tape have on the thermal transfer? Is it a positive effect because there's much better surface area contact between layers or is it negative because the adhesive is an insulator?

The above really only compares tape to foil wrapping. Anecdotally, either is better than nothing.

And will the heat cause the adhesive to run and make a mess inside the light?

I can't say for the copper tape but the aluminum tape is specificly made for sealing joints in furnace ducts. It would be a **** poor product if the adheasive started running from the heat of a furnace. It's very sticky and once you put it on, you'll have a hard time removing it.

Big_Ed said:

And will the heat cause the adhesive to run and make a mess inside the light?

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I'm curious about this too, with the copper tape. The description for the roll I ordered says:

First quality self adhesive copper foil tape with solvent based acrylic adhesive which is suitable for indoor and outdoor use​

Great for the back of guitar pickguards, sheilding cavities, eliminating electrical hum and noise​

Can be used to replace tracks on electrical circuit boards and printed circuit boards​

Can be soldered​

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