# SBT-90 Build (First custom build)



## Bertn (May 25, 2012)

After months of planning and buying I have finally finished my SBT-90 build. I must say the most challenging part of the build is packaging. 

Parts List:

Maglite D switch assy. I bought a $50 torx set but it was no help so I finally drilled out the original switch assy. It's good the new switch assy. came with the appropriate torx driver. 
http://maglitesales.com/maglitestor...-D-Cell-Switch-Assembly-KIT-NEW-Style-108-208 



SBT-90 emitter. 
http://www.mouser.com/Search/ProductDetail.aspx?R=SBT-90-W65S-F71-MA102virtualkey65110000virtualkey896-90W65SF71MA102



DIWdiver's IS1006-1025 driver. 
http://www.candlepowerforums.com/vb/showthread.php?264687-Adjustable-10A-linear-LED-driver-New-and-Improved!



Thermal pad for the driver. 
http://parts.digikey.com/1/parts/988588-thermal-pad-220-009-sp600-sp600-58.html



Heat sink for the driver. I used a bench grinder to shape the aluminum (length, width, & height) to fit inside of DW's heat sink and attached DIWdiver's driver with Artic Alumina. 
http://www.radioshack.com/product/index.jsp?productId=2102857&CAWELAID=107591883



DW's heat sink. 
http://www.candlepowerforums.com/vb/showthread.php?284083-SST-50-amp-SST-90-Mag-Lite-Kit&p=3461444#post3461444



16mm aluminum reflector 
http://www.britelumens.com/



Feilong batterys/battery 
http://www.novaeproducts.com/apps/webstore/products/show/1846436



Battery charter 
http://www.lighthound.com/Ultrafire...3-37-volt-Lithium-Battery-Charger_p_3669.html


Original switch housing - I removed the plastic bulb/led housing with a grinder to allow for the SBT-90 heat sink. (See later pics)







The switch assy. separates from the outer plastic housing above without hardware removal (just push). 






The switch itself separates from the blue plastic which contains the ground screw.





In order to use the driver with the stock switch assy. I had to isolate the positive switch terminal from the battery terminal (refer to DIWdiver's schematic). The two outer contacts are bent to make contact with the push button switch, the positive terminal of the battery, & the light source. I simply straightened the side which would normally contact the positive terminal of the battery.





After placing a small amount of solder on the contact which mates to the positive terminal of the battery to ensure a good connection and carefully soldering all the wires between the LED, driver, & switch assy. I was finally ready to apply power to the LED. (It's not the best job I know.... But it was difficult to get all of this stuff to fit into such a small housing.)
















The heat sink is not perfectly flush with the maglite housing but after installing the reflector and lens without the base everything fits nicely. The reflector base is used with the COTS maglite to vary the height of the lamp relative to the reflector and produce a different beam pattern.
















So after the build was finally finished I charged the feilong batteries with a ultra fire WF-188. Unfortunately I fell asleep and when I woke up one battery was charged and one was not. The battery that did not charge only has a potential greater than ~3V briefly, after applying a load it drops down to 1.5V. I'm not sure if the battery was DOA or if the charger is to blame. Either way with one good battery I was able to get over 5A of current flowing through the LED.











Beam Shot







So I have now ordered two new batteries from China. Once they arrive I will post updated current measurements along with beam shots.


New batteries on order 
http://www.easylightbuy.com/feilong-37v-6000mah-32650-liion-battery-2pack_p711.html

NEW BATTERIES HAVE ARRIVED







In order for these new unprotected batteries to make a connection with the switch assy. I had to build up a solder mound. 





After a slight modification to the tail spring it was times to take some current measurements.





Over 10 amps I am most impressed!





This beam shot does not do it justice. It's really really much brighter than it appears.






There are a lot of posts on this forum regarding current measurements and how the measuring device adds significant resistance which affects the current measurement (e.g. the measured current is less because the resistance of the leads etc. are impacting the circuit). I'm not sure this is the case here (just my opinion) because I was able to measure over 10 amps of current. The meter actually started beeping and flashing I'm really surprised I didn't blow the fuse....

I wish I would have taken some pics of the light output outside it was pretty impressive. But the emitter is only rated for 9 amps of current and heated up quickly which means it didn't last long... By long I mean less than five minutes of continuous use before the emitter was toast. I had used the light in short intervals (less than a minute at a time) not allowing it to overheat but decided this was very impractical. After spending the time and money to put this build together I am disappointed that I ended up with a light which could only be used for a few seconds at a time. 

Any ideas on what a practical amount of current would be to use with these types of emitters? I would think something around 5 amps would possibly be OK for extended periods of use but I have yet to do any testing. Considering the limited thermal management available due to the size of the host it's hard to say without some experimentation. I do believe the thermal management is the limiting factor with a build like this. 

I think my next build I will be more conservative and focus on practical use instead of maximum lumen output.


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## wannabe333 (Jun 3, 2012)

could you pls explain how you cut the recess spring of your tail cap and make it lie flat at the botom,? thanks


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## The_Driver (Jun 3, 2012)

If you want to really use this emitter to it's full extent you have to relow solder the led onto a copper heatsink or at least a copper pill that is press fitted into the heatsink. Kevon from Lambdalights does this in his Varapower lights. I have a Varapower Turbo V2 and I think it does around 13A, but I'm not sure. I can use it for maybe 5-10min outside before it gets too hot to hold. I have a de-domed sst-90 in my light which is basically the same thing as the sbt-90. I also think you need a much bigger reflector for this led to make sense. The good thing about it is that it will produce more lux (more throw) than a normal sst-90 would when using the same reflector. I think you should at least you a rebel mag led reflector (Lambda got around 90,000lux with these).

10A with a single li-ion battery is really good by the way.

And yes, when measuring high current with a multimeter you need very short test leads with a high-gauge wire to get accurate readings. It needs to be much thicker than normal test leads. The measurement will still not be accurate though, because the thick wires miht actually have a lower resistance than the tailcap of the light. 

I hope this helps.


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## Bertn (Jun 3, 2012)

wannabe333 said:


> could you pls explain how you cut the recess spring of your tail cap and make it lie flat at the botom,? thanks



Unfortunately I do not own a Dremel tool so I placed the area of the spring I wanted to cut inside the corner (e.g. outer edge) of a vise and used a pair of pliers to bend the metal back and forth until it broke. The spring is shaped like a helix so in order to ensure the spring would not fall out and lay semi flat in the bottom of the tail cap I used two pairs of pliers to expand first bottom circle to a size slightly greater than the inner diameter of the tail cap and compressed the bottom circle to lie in a plane close to the start of the second circle from the bottom. 






The bottom of the tail cap has a coating which must be removed to allow the current to flow through the case/spring. I removed the coating using a carbon Dremel tool brush with a drill.


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## texas cop (Jun 3, 2012)

Buy a Dremel, one of the best do about anything tool.


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## Bertn (Jun 3, 2012)

The_Driver said:


> If you want to really use this emitter to it's full extent you have to relow solder the led onto a copper heatsink or at least a copper pill that is press fitted into the heatsink. Kevon from Lambdalights does this in his Varapower lights. I have a Varapower Turbo V2 and I think it does around 13A, but I'm not sure. I can use it for maybe 5-10min outside before it gets too hot to hold. I have a de-domed sst-90 in my light which is basically the same thing as the sbt-90. I also think you need a much bigger reflector for this led to make sense. The good thing about it is that it will produce more lux (more throw) than a normal sst-90 would when using the same reflector. I think you should at least you a rebel mag led reflector (Lambda got around 90,000lux with these).
> 
> 10A with a single li-ion battery is really good by the way.
> 
> ...




Thanks for the reply!
Copper vs. aluminum interesting. Does he mount the LED's further into the body of the heat sink? I checked out his website and there is advertizement regarding heat sinks but I didn't see any for sale but I will contact Kevon for more info.

The reflector is something I placed a low value on since this was my first build. I was looking for performance from the individual pieces (i.e. the LED, driver, batteries). I bought the standard aluminum reflector to avoid heat/melting issues. Ultimately I want light output which is collimated not focused. I almost procured the following lens but due to price and mounting complications I decided it was not worth it. The focal length is close to the emitter/lens distance. 

http://search.newport.com/i/1/nav/1.../facetValue01/x5/facetValue10/x6/facetValue04

The over 10 amp measurement was taken using two unprotected Li-ion batteries in series. The first current measurement of over 5 amps was taken using one battery. 

The resistance of the series FET and sense resistor is ~0.02 ohms. I'm not sure what the on state resistance of the LED is. When measuring current with a meter in series with a circuit you are introducing additional resistance. For example, internal resistance of the meter and lead resistance. 
I = V/R for a DC circuit. The voltage is ~constant and any increase in resistance reduces the current measured. If the resistance of the leads/meter is small relative to the resistance of the circuit then the impact is negligible but if it's on the same order of magnitude then it's has a large impact. It's definitely something to be mindful of when taking measurements. I guess a better approach would be to measure the voltage across a small resistor with a meter and compute the current.


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## Bertn (Jun 3, 2012)

texas cop said:


> Buy a Dremel, one of the best do about anything tool.



Next on my list of items to buy items.


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## The_Driver (Jun 4, 2012)

Bertn said:


> Thanks for the reply!
> Copper vs. aluminum interesting. Does he mount the LED's further into the body of the heat sink? I checked out his website and there is advertizement regarding heat sinks but I didn't see any for sale but I will contact Kevon for more info.
> 
> The reflector is something I placed a low value on since this was my first build. I was looking for performance from the individual pieces (i.e. the LED, driver, batteries). I bought the standard aluminum reflector to avoid heat/melting issues. Ultimately I want light output which is collimated not focused. I almost procured the following lens but due to price and mounting complications I decided it was not worth it. The focal length is close to the emitter/lens distance.
> ...



Kevin is very active over in the fnf forum. Check out this, this and this thread for some info about his recent and current lights. He does not sell heatsinks by themselves as far as I know, but maybe you can convince him. The most feasible thing to do for you might be to use a sbt-90 on a star and use set-scerws to press it onto a copper heatsink with a thin layer of arctic silver in between. Thats the best thing after soldering the led onto the heatsink. Some of the modders on cpf should be able to make you a heatsink with 2 or 3 holes for the screws.


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## Bertn (Jun 4, 2012)

The_Driver said:


> Kevin is very active over in the fnf forum. Check out this, this and this thread for some info about his recent and current lights. He does not sell heatsinks by themselves as far as I know, but maybe you can convince him. The most feasible thing to do for you might be to use a sbt-90 on a star and use set-scerws to press it onto a copper heatsink with a thin layer of arctic silver in between. Thats the best thing after soldering the led onto the heatsink. Some of the modders on cpf should be able to make you a heatsink with 2 or 3 holes for the screws.



Cool thanks for the links!


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## The_Driver (Jun 5, 2012)

Please keep us updated, your findings here are very interesting


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## ma_sha1 (Jun 5, 2012)

sorry to see this, did you use arctic silver?
Did you clamp the led down to cure? make a spacer that could push down the edge/corners of the led & clamp gently during curing

the led to theatsink heat transfer is the bottle neck here, need best thermo adhesive with pressure for thin est application to achieve heat transfer that can handle 9-10A. I wouldn't go more than 10A, you'll probably need direct dolering after 10A but DIWdriver is very precise, 1025 should have 10A max, probably your multimeter not precise so it reads 10.6A.


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## Bertn (Jun 5, 2012)

ma_sha1 said:


> sorry to see this, did you use arctic silver?
> Did you clamp the led down to cure? make a spacer that could push down the edge/corners of the led & clamp gently during curing
> 
> the led to theatsink heat transfer is the bottle neck here, need best thermo adhesive with pressure for thin est application to achieve heat transfer that can handle 9-10A. I wouldn't go more than 10A, you'll probably need direct dolering after 10A but DIWdriver is very precise, 1025 should have 10A max, probably your multimeter not precise so it reads 10.6A.



Yep. I used Artic Alumina to permanently attach the LED to the heat sink. As for clamping the LED down during the curing process I definitely could have done a better job. If you put the LED housing (the detachable portion) into the opposite end e.g. the bottom of DW's heat sink the LED itself will stick out above the body of the heat sink. So after the adhesive was applied I just turned the heat sink upside down so the face of the LED was on the table and the weight of the heat sink was the only clamp. 

I agree DIWdriver's driver is very precise and my meter has never been to the cal lab so I'm sure it's not 100% accurate. 

Your list of builds is pretty impressive . I didn't search through all of them yet but have you had any success with ~10 amps through an LED? Also, any suggestions on heat sinks aside from DW's for the LED and what about driver heat sinks? 

I'm not giving up yet though. After I'm done licking my wounds it's back to the drawing board. I think I will just buy a new LED and finish the build paying close attention to ensure a good thermal connection between the LED/heat sink and also try and improve the thermal management of the driver. Part of the FET housing is actually melted so at first glance you would think it's toast as well but the drain to source is not shorted so I guess it's still ok but not positive. I have a new driver I will use instead though. It is apparent better cooling would be required for any extended period use at this current.


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## The_Driver (Jun 6, 2012)

Bertn said:


> Yep. I used Artic Alumina to permanently attach the LED to the heat sink. As for clamping the LED down during the curing process I definitely could have done a better job. If you put the LED housing (the detachable portion) into the opposite end e.g. the bottom of DW's heat sink the LED itself will stick out above the body of the heat sink. So after the adhesive was applied I just turned the heat sink upside down so the face of the LED was on the table and the weight of the heat sink was the only clamp.
> 
> I agree DIWdriver's driver is very precise and my meter has never been to the cal lab so I'm sure it's not 100% accurate.
> 
> ...



I hope you are successfull, but do remember hough that even at full power a light with this led wont seem much brighter than a hard-driven xml light.


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