SST-90 Build Project Help

[Yeoman]

Hi everyone-

I'm building a flashlight as part of a tech competition, and to hopefully stand out, I'm doing it with the powerful SST-90. That said, this is my first flashlight mod, so I thought it would be smart to get some help from people with experience doing it. Right, onto specifics-

-I'm using (1) sst90-wm-df

-I've heard that the 2/3D Maglights make for a nice body, but I think that using the body of a 6v lantern would give me more space for the batteries, a heat sink, and a larger reflector.

-Batteries. As the sst-90 runs at 3.7v, I thought running 18650's in parallel would be a good choice.

-How/on what do I mount the LED? I realize it will be getting hot but I have seen builds here using the stars that make the SSR-90, and all sorts of other home made or scavenged pieces.

-What kind of wire should be running to the leads? I don't think I'll be taking the LED up to its 10A max, but even so the current will be large and the leads are small.

I'm sure I'm missing a number of things I should be thinking about, so any suggestions to the above to get this project rolling are appreciated. I'm learning as I go, so be generous in you explanations please


The heart of the project-

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[irv_usc]

I'm no expert, but I guess I have a question. If you are planning on a larger lantern, why the SST-90? you could go with a CSM-360 and use a giant hunk of aluminum/copper as your heatsink.

As far as your questions.
- A lot of people choose MAG's because there are already a few different heatsink options out there that you can just buy here on the forums. It seems that running the sst-90 on DD from 3-4 nimh's has been done quite a few times with some useable results.

- Batteries depends largely on the size/space of your host. if you have enough space, why not go with a 26500 or 26650? IMR cells would be preferred for the high current capabilities.

 

[Al Combs]

+1 to irv_usc's suggestion on using IMR batteries. Their lower internal resistance makes them better suited to this type of application. It sounds like you're talking about a direct drive (no regulator) type of an application. A DMM with a 10 amp scale is a must for direct drive testing. That can be kind of a crap shoot as far as the forward voltage of your LED goes. My SST-90's Vf at full power is 3.88 volts at the moment. It hasn't finished settling in yet. If you have a bunch of fully charged IMR26650's in parallel, it just might fry an SST-90. It really depends on which LED you get. They are all a little different. Also be aware that the Vf of an LED drops as it gets hot. Your meter may say your LED is getting 9 amps in testing, and you still might end up cooking it.

-I've heard that the 2/3D Maglights make for a nice body, but I think that using the body of a 6v lantern would give me more space for the batteries, a heat sink, and a larger reflector.

A lantern would probably be a better choice for heat management. Everyone putting a 30+ watt LED in a MagLite has to deal with the intermittent use concept. It's just too much heat for continuous use in a light that small.

-How/on what do I mount the LED? I realize it will be getting hot but I have seen builds here using the stars that make the SSR-90, and all sorts of other home made or scavenged pieces.

Usually if you buy a bare LED, you've already got something in mind. Otherwise you buy a star. I had seen a post indicating it's possible to reflow an SST-90 onto a star intended for a Cree XR-E emitter. The second of those two shots shows the thermal vias of the SST-90 is much wider than the mounting surface on the star. Since the emitter is only 3*3 mm, I'm not sure if that really presents a problem. I'm saying this because while I've seen a number of places you can buy a blank Cree star, I've yet to see an empty Luminus star. I recently posted a build thread where I reflowed my SST-90 onto a small piece of copper bar. Perhaps you can get some ideas from that. Heat pipes look very promising for use with high powered LED's. Although I've yet to see them in a project.

-What kind of wire should be running to the leads? I don't think I'll be taking the LED up to its 10A max, but even so the current will be large and the leads are small.

I used 20 gauge wire and had no problem getting over 10 amps. The wires were cool to the touch. Here is a chart showing thickness vs current. I took their reference to chassis wiring to mean short runs (like in a flashlight). Some of the more conservative tables say you need 18 gauge for that much power. I had no problems with 20 gauge.

Good luck with your project.:twothumbs

 

[Walterk]

Heat pipes look very promising for use with high powered LED's. Although I've yet to see them in a project.

Well, I'ts on its way, I am working on it. I plan on using this for a single SSR90 @ 10Amp:

I used Dremel-like to get me the 5mm heatpipes from a laptop heatsink. Bending it back straight was easy, done by hand. Glued with arctic silver.
It was originally force ventilated and used for a Pentium 3, so I guess it would be rated at something like 70 Watt. With natural ventilation in open air I hope to get 30 Watt. (The copper is much oversized, and the aluminium is for aligning and mounting only. ) Have to test it yet, finalizing wiring for preliminary setup.

 

[js-lots]

On my sst 90 build I was originally using 3 nimh sub c's but wasnt getting the results I expected. My results were a little more promising with a single 26650. I believe the forward voltage of my led may be a bit high. I went to 4 nimh instead. Fresh off the charger my led went to an angry blue. Turned it off and on few more times. The led would start white then start turning shades of blue. After I let the batteries settle down a little bit the led was pulling about 7/8 amps. However the runtime is only so so. If you have a driver Li-ions are the way to go IMO. taskled has a few options. Also people have used shinging beams driver paralleled with 7135. If you search around a bit I have read that 18650 imr parallel is another good way to go for powering your led. Just be careful with them fresh of the charger. May be to much for the led to handle. Good luck