Triple XP-G Marwi conversion

[PScalfano]

Warning: new member content. :help:

This is a work in progress. I picked up an L332N-MC from lux-rc and integrated it into a marwi light body + heat sink from el34's website. I used arctic silver epoxy to attach the driver/LED board to the heat sink, and also to attach the heat sink to the light body. For the cable/connector, I went with a magicshine extension cord from geoman. I am using a magicshine battery to power this light. I went with this particular switch because it easily allows me to change modes once the light is on by lightly pressing the button but not engaging the switch.

I still have to work on the water sealing and front lens. I would love to hear any comments or constructive criticism from you guys - this is my first build. I would not have been able to do this without the information you guys share on this forum. I really appreciate everyone sharing their knowledge and expertise.

Thanks for looking!

 

[BrianMc]

Nice adaptation. One EL34 was thinking of from the first posting of it over on MTBR.

One caution, relates to heat at max current. I can't remember if that board is set at 1.4 or 1.5 A max, but you have three XP-G's which are 3.5 Vf at 1.4 A and 3.55 at 1.5 so between 15.7 and 16.0 Watts about 15-20% of which becomes light, so between 12.5 and 13.6 watts of heat. I'd guess about 8 square inches of body not including the bezel, since the bullet shaped light is about 7.5. You can measure and calculate that easily.

The bezel is about another 1.3 sq inches including the inner lip, but on my lights the bezels feel cooler than the body as there isn't a good thermal path through the threads and they are cooled both sides, but my max is 1 A. I am still messing with mine and need to open it easily. I did think that a bit of Arctic Alumina thermal paste (NOT epoxy) on the threads would help the bezel participate as a thermal radiator more effectively, but will make a clean and easy opening a problem.

Bottom line is that in the worst case, you have about 6/10 of a square inch of radiative surface per watt on max power. Definitely pushing it. If high is reserved for fast downhills, or cooler outdoor temps only, there is a lot of air cooling because of air flow or temperature gradient and you should be OK. I think the board has a temp cutoff in it, doesn't it?

Triple XPGs @1 amp (10 watts consumption and 8 watts of heat) get hot in my Marwi housings but not too hot to touch, or to trigger the 50 C temp power down of the Bflex drivers, in sunlight at 95 * F at my usual average of 15-18 mph. (daytime running light use). Mostly I run them at 0.5 amp or on flash and they are just warm.

Beamshots next...

 

[PScalfano]

Hi BrianMc, thanks for your informative reply.

According to the data sheet, the L332 MC-N supplies 1.1A to the LEDs. With the magic shine battery providing 8.4 volts, the consumed power is around 10.75-10.8 watts. Hopefully I'm on the more conservative end of the thermal capabilities of this marwi housing.

I knew I wasn't going to get away without beamshots. I hope indoor ones will do, because I do not have a yard. Maybe tonight...

:thanks:

 

[BrianMc]

According to the data sheet, the L332 MC-N supplies 1.1A to the LEDs. .. the consumed power is around 10.75-10.8 watts. Hopefully I'm on the more conservative end of the thermal capabilities of this marwi housing.

Sorry, I was running from memory (dangerous) wrt 1.4 or 1.5 A. So many max currents were discussed, I lost track in that thread and I am not in the market for a wider beam light, so though I like it, it isn't for me at this time.

I am putting 3.3 Vf x 3 series XP-Gs x 1 A out of a Bflex for 9.9 watts through the LEDs and another 1-1.5 through the BFlex. Call it 10.4. EL34's P7 adaptations run 3.7 Vf * 2.8 A for 10.4 through the LED in your exact housing. Neither of us or the myriads of EL34's friends and customers have overheat issues. So the bodies handle 10-11 watts just fine (about 8 watrts of heat and about 8 sq in, so right at the 1 sq in/ watt of heat index of radiative surface area.

The extra output an XP-G can give above 1.0-1.1 A is less efficient, so you get a bit more light but much more heat. Running three at 1.1 A is more effective (more light for same power) than 2 are when run at 1.5 A.

 

[PScalfano]

That is great to hear!

I'll work on the water sealing as time allows and get some beamshots next.

:twothumbs

 

[Tidra]

Water sealing is the biggest problem with those Marwi housing's, unless you just dip it in to the silicon,...

 

[PScalfano]

Yeah I'm still working on the water sealing part... but I took a few beamshots tonight:
low

med

high

Vs. Magicshine

 

[BrianMc]

I assume those are the narrowest optics he has for the light engine?

When you think that the Magicshine has a single large reflector, and the triple XP-G three small lenses, the outputs are closer than I'd guess.

I don't know that you will achieve waterproof because the sliding contact of the mount/back with the body is difficult, the lens o-ring can be hard to seal if the lenses stick out a bit, but water resistant is doable. I ran a bead of silicone in the back/body seam and the bottom before fastening. I don't plan on using either of mine underwater or leaving then in a downpour overnight. Time will tell. I know I will be updating and modding it and I am not running in races or some supercritical situation where I can't limp home on backup lights, so making it hard for water to get in seems to me to be good enough.