So I have this old ultra-cheap host that I’d like to upgrade but I’m concerned about heat dissipation and unsure what current to feed it. This weekend I read through a few dozen old and very old forum threads and didn’t find an easy gimme answer to this, but did see one about a similar host/components (without a final solution) and an interesting one from Barkuti about bare-board dissipation.
Picked up this “3 watt” light maybe fifteen years ago for a couple bucks. Now I’m going to spend about $35 to turn it into something useful. lol. It was a 2-C cell light with an old cheapie emitter, pretty much junk, but I made a plan to refresh it. Picked up some Keeppower protected 18500 cells (Panasonics), found that the reflector and lens for a Convoy M1 fit perfectly into this host, have a new switch on the way. 20mm mcpcb and 20mm driver. But the big question is how much heat this can handle, and unfortunately I can’t test the output of the original driver since it died long ago (assuming it was less than one amp).
It has one of those dang hollow donut aluminum pills. The mcpcb has maybe a 1mm ledge to rest on but most of it is bare-air…straight down to the driver. There is some mass, but that big hole of dead air. About 8mm space or more, so I can fit several buck driver designs in there (already have a couple of them from MTN, one on the way from Simon, and will likely be ordering a few more from KD just to have around). Using a 20mm —> 17mm adapter ring might gain me another smidgen of space.
I’m considering adding some of those silicone thermal blocks in the space but I don’t necessarily want to transfer heat down to the inductor or driver components either. I could possibly do a copper plug or solder a penny or something, but really I’m not sure how much heat can nicely transfer from the pill to the host body since the threads are somewhat loose and the pill is rather short anyway (will likely put a little thermal compound in the threads, messy as that is). The head is fairly thick and uses a thick aluminum retaining ring to secure the reflector, and the M1 reflector being aluminum may help in heat dissipation vs. the original plastic one. The main body isn’t thick, no fins, but it’s not super thin either.
Emitter choice is undecided at the moment until I have an idea of the buck driver current…sticking with 3V, though, and considering LH351D or SST40, depending. Or…would a 6V emitter put off any less heat in a buck at lower currents?
Other than swapping a couple early emitters, I didn’t get into modding lights until I had many with good host designs, so I’m not sure what these old cheapie hosts are capable of. I’d prefer not to unnecessarily fry a driver or emitter if I can help it. I’m thinking that 1A should work just fine….what about 1.5A or 2A? This host may have less cooling ability than an S2+ body, so going above 2A with poor sinking seems like maybe a bad choice, despite being larger in diameter.
Going for simple single mode utility light here and +/- 350 lumens would be fine, but more would be nicer of course. What would you suggest for current, what have you found in cheap mods like this?