improving cheap chinese bike light?- help please

I bought some cheap bike lights. One has 4 emitters in a round barrel, the other has 5. They each claim Cree XML-T6 emitters. Both seem to work pretty darn well. They don't get terribly hot though. I took them apart and found no thermal bridge between the piece of aluminum that carries the emitters/driver and the outer barrel (which barely has any fins). Wouldn't this make the guts get REALLY hot? that can't be good for it right?
I am thinking I could just squirt some thermal paste or thermal epoxy in there and would improve heat transfer immensely. Is it that easy? Do I need to worry about shorting something out? Will it extend the life or make it brighter longer?
Any help appreciated!

Noob cheap flashlight questions

Hi
I just bought some cheap lights for a project I'm working on.
http://www.ebay.com/itm/1800LM-Ultr...ht-/161171470407?ssPageName=ADME:L:OC:US:3160

I am sure they are nowhere near the claimed 1800 lumens, but they are seriously bright for such little things. But only for about 20 minutes. Then they cool off and the light output goes WAY down. I wouldn't expect the single 18650 to crank that hard for long but I left them on anyway. I finally turned them off at about 60 minutes and there was almost no light at all, but they were still trying. Then I charged the batteries and put them back in.

Here is the part I did not expect: with fresh battery charge the lights were still very dim. At tightest focus when the beam is square and you can see the emitter it looks like about 80-90% of the emitter is "burned out." Is this normal? The batteries work well in other lights, so that is not the problem. Are they permanently damaged? Did they get too hot? Did I do something wrong or just another case of Chinese junk?

any help appreciated
Thanks!

Re: Noob cheap flashlight questions

It is almost sure they got too hot and are nearly dead now. :shrug: Good heatsinking is VERY important.

Re: Noob cheap flashlight questions

Icarus said:

It is almost sure they got too hot and are nearly dead now. :shrug: Good heatsinking is VERY important.

Click to expand...

+1

Sounds like they were designed to self destruct.

And no, it's not that simple. Thermal glues and compounds are designed to be used in very thin, wide applications. Their thermal conductivity is really very poor compared to aluminum. That's what you needed, a block of aluminum to bridge the gap between the "heatsink" and the body. Then some compound to fill in the thin gaps that are left.

Re: Noob cheap flashlight questions

DIWdiver said:

+1

Sounds like they were designed to self destruct.

And no, it's not that simple. Thermal glues and compounds are designed to be used in very thin, wide applications. Their thermal conductivity is really very poor compared to aluminum. That's what you needed, a block of aluminum to bridge the gap between the "heatsink" and the body. Then some compound to fill in the thin gaps that are left.

Click to expand...

Agreed, but wouldn't some compound bridging the gap be better than air? I estimate the gap (radially) to be about .010" all the way around. Would I have to worry bout it turnig liquid at temp and running to the back where the exposed wires are and causing a short?
Thanks

Re: Noob cheap flashlight questions

You could try some copper tape. It is on back order at illumination supply and I couldn't find any on the cheap Chinese sites I checked.

Re: Noob cheap flashlight questions

Another point to your first post. If the body of a flashlight doesn't get hot it doesn't means that the light has a good heatsinking. It usually means the opposite especially with cheap flashlights. In your case maybe just get a different driver and only use 2-3 XM-Ls that should be plenty of light too.

rayman