Review/Overview of LumensFactory SST-90 M Series Turbo Head Unit

mdocod

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Mark sent me one of these to check out and share with you all over a week ago. I've had a chance to use it and test it enough now to share a thorough overview/review of the unit.



SST-90 M specifications (from LumensFactory):

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-Limited Production

-High Output Lumius SST-90 LED (Max Output 1600 Lumens)

-9V to 13V Regulated Input for Maximum Flexibility

-3 Mode with Memory (5%-30%-100%)

-Maximum Current Input to LED at 6000mA

-HA 3 Anodizing on the Head Unit.

-Constant Output

-Unique Reflector Design

-Precision Machined Aluminum Reflector

-High Temperature Resistant Light Orange Peel Coating

-Every Reflector Module is Pre-Focused for the Ultimate Spot

-Compatible with all Flashlights with M Series Sized Head Units.

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There is a lot to say when dealing with a product that pushes up against lots of barriers. Lots of power consumption and lots of heat and lots of configuration limitations means that there is a lot that needs to be covered in order to really fully understand the unit. This Turbo-Head has it's ups and downs and I hope to fully cover all the pertinent information that an educated consumer should be aware of before pulling the trigger on one.



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First things first: A rundown of how to power the unit and what configurations will work:



Perhaps the most important consideration is that the unit will not operate below ~7V input, and has a power consumption in the 25-30W range. This criteria helps us form the basis of what types of battery configurations could theoretically work. When the input voltage drops below ~7V on high mode, the unit tries to drop into low mode, the drop in load results in the battery voltage rising high enough to continue to sustain operating on low for awhile (how long would depend on the specific cells/configuration used). A fresh pair (2X) of brand new large format IMR cells can probably run the unit for a short time on high before dropping too much voltage. From what I can tell thus far, the power consumption is going to be about the same whether you feed this unit 7V or 13V or more. I'm always measuring right in the ~28W ballpark regardless of input voltage. It would stand to reason, that if the power consumption is staying constant through the range of possible drive levels, that the output should be fairly constant over the range as well. I do suspect that at the very low drive voltages (below the minimum 9V rating) the efficiency on the input side of the circuit probably drops off some purely due to higher losses from resistance (more current, less voltage).



Since the unit is always trying to draw about 28W on high, you can figure your current consumption by taking the approximate voltage of the pack under a load and dividing that into ~28W. The rated 9-13V range operates with a current draw of ~3.1A@9V down to ~2.2A@13V.



The 9-13V input suggests a standard configuration of 3 li-ion cells as being required to operate the unit. In PMs with Mark, he did suggest that the light actually works on 4 li-ion cells as well. I'm not sure if 4 cells are officially supported however I did briefly test this configuration and regulation seems to work correctly on 4 freshly charged li-ion cells (input current drops in accordance with increased supply voltage). You can plan on sub-2A drain rates through most of the discharge on 4xli-ion cells.



The absolute minimum LiCo cell size/configurations that can be used with reasonable safety would be as follows:

3x18500/17670 or larger (ideally protected)

4x17500/14670 or larger (must be protected to prevent over-discharge)



Any 3xLiMn (IMR) cells should be fine. Even the little 16340s, but they will wear out quickly driving a load like this. I'd suggest against using LiMn (IMR) or unprotected LiCo cells in a 4 cell configuration because the unit will be more apt to over-discharge the cells before shut-down. Remember, the cutoff is around 7V, which will probably result in cells being a bit below 3V open circuit in a 3x configuration if the 7V limit is relied upon to prevent over-discharge in high mode. In the low and medium modes it may be possible for this unit to over-discharge a 3x configuration of unprotected cells so the user should try to avoid running the light all the way down.



Various configurations of LiFePO4 cells with enough voltage (4+ cells) would also work, however I don't see any benefit to going this route.



The M6 stock battery adapter is wired 3S2P and might not provide enough voltage to run this unit on regular CR123s (it would likely work fine on low and medium mode, but high would be hit and miss), loaded with IMR16340s it would work fine.



CR123 primary cells should probably be avoided to run this unit in most configurations because of the drain rates in excess of 2.5A that are likely to occur towards the end of the discharge (the unit will draw up to ~4A at the end of the discharge before dropping down into low mode). Though if used with say, 6+ cells in series (hopefully it could handle the ~18+V initial on lower modes, not sure), or perhaps a 4S2P or 5S2P configuration, it might work reasonably well, (just very expensive to operate with the risk factor of having a large number of CR123s operating together).



LumensFactory suggests against the use of any clicky switch in conjunction with this head unit. This is of course to cover their butts on a liability front. Ill give a little different perspective: A surefire clicky that can handle 2.5A, or any after-market clicker that can handle that or better should be able to handle running this unit reasonably well. I'm not going to guarantee it (it's on edge), but under most configurations through most of the discharge the current draw isn't likely to be above ~2.7A for any significant length of time. On a 3xli-ion cell configuration, right towards the end of the discharge when the voltage of the cells makes that final nose dive the current draw will ramp up to ~3.7A quickly, but this will generally only last a few seconds as the protection of the cells is about the kick in, or in the case of unprotected cells, the unit is about to force a lower mode due to dropping below 7V (may hit as high as 4A in the final seconds here). The only 3xli-ion configuration that I would seriously not suggest using a SureFire clicky on would be on 3xIMR16340s, which are probably going to sag quite a bit under this draw and result in higher average current flowing through the switch. In the case of a 4xli-ion configuration, they should be protected cells, in which case, the input voltage would never be any lower than ~10V before the protection trips, at which point the unit isn't likely to be drawing any more than ~2.8A. Through most of the discharge on 4xli-ion cells, the current is going to be around or below 2A, even the 2A rated Seraph clickers could probably run this head in a 4xli-ion cell configuration.



A clicky switch would probably be the preferred way to run a multi-mode unit like this... Trick is, you have to mate up a scenario that matches a clicky to a true M series head design that simultaneously supports a large enough battery pack to fit the unit (does not work with C-M adapters, more on this later....)





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Multi-Modes and the recommended momentary/twist switches...



The 3 mode operation is something I could do without for an M series light. I'm very surprised to only see this turbo-head offered in the 3 mode version. Operating multi-mode regulators from twisty/momentary switches is not my cup of tea. I find myself accidentally switching modes or skipping modes when I do not intend to. The best way to combat these usability issues is to have all the contacts in the switch good and cleaned up so that contact is predictable and repeatable. With practice I am getting used to it though. The saving grace is that the memory function does work with predictable repeatability. I think if I were going to implement this unit as a regular part of my configurations, I would want to pick up a C-M body so I could get a clicker for it.



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General thoughts/Considerations/Pictures...



In each photo, the new SST-90 head is pictured to the right of the older P7 head for comparison.



100_4414.jpg




Mounted to an M6 body in the photo above, we can see the new SST-90 emitter shoehorned into the familiar HA aluminum head from the Seraph P7. Many CPF members found that the platform was adequate for SST-50/90 installations and had done mods to the P7 head to support the newer LEDs. The reflector design it comes with complemented the P7 and the large format dies well. Conversion to the new emitter requires no change in the reflector. On closer inspection I believe that the reflector geometry is unchanged from the P7 model. The texturing is different between the two, with the new SST-90 head having come with a slightly less aggressive texturing. I assume that this is just regular variation (we see this in all brands) from unit to unit since both units claim to have the same light orange peel texturing in the specifications. The SST-90 does seem to give me a slightly more pronounced beam with the different texturing, but Im not sure if this has more to do with the texture or the die/lens/emission pattern characteristics.



The P7 head had a nice cap that concealed all but the LED die and protective bubble over the die by threading onto the tower. The New SST-90 looks a little less refined as its showing the lead wires and round board that the SST-90 is mounted to.



100_4418.jpg




The tower module that holds the regulator and LED has changed to a shorter length and larger diameter. This change was likely to accommodate the higher current regulator. The shorter tower module has been compensated for by longer springs. Unfortunately, The new Tower module will only fit down in the head of a true M series body. The C to M adapters will not do the trick here. I believe this is why the new head does not carry the Seraph name as it will not work on a Seraph body. I suspect someone handy with a machine tool might open up the business end of a C body flashlight to support it though (I may give it a try).



I had hoped that the new model would solve one particular problem I had with the previous P7 model...

The inside lip at the base of the units (just in front of the threads) was machined too large a diameter to properly seal against the M6s factory O-ring. If you submerge the M6, even if properly lubed up, water will likely get in at this seal. I was under the impression from Mark that my P7 evaluation unit was a pre-production unit and that the production models had solved this problem. Unfortunately, the design was unchanged. My suggestion would be to find a thicker O-ring to use with ALL of these LF M series turbo-heads.



100_4419.jpg




Notice there is some black tape or something wrapped around that center spring? It's there to help prevent shorting. Unfortunately, this band-aid to a design flaw isn't concealing the wound entirely....



The Unit comes with a piece of paper with specifications and a section labeled: Important!! Please Read Before Using.

In the list of recommended reading, perhaps the most important thing is #3, which is highlighted in bold:

3. It is very important that users install the turbo-head before installing any batteries (or battery case for M6). This will prevent the chance of shortage. Again, this is very important.



The new longer springs, especially the center spring, pose a shorting hazard. If you try to install the head on the flashlight body after the cells (or battery pack) has been installed, the center spring can bind and fold over sideways and short against the aluminum body as a result of the torsion effect presented by spinning down the head against the springs. I have been able to replicate the problem but I have only been testing the unit with protected cells so have had no adverse effects except having to remove the battery pack and re-install it. I have not been able to replicate the problem under normal operation where the head is installed and battery/pack is being removed and reinstalled frequently. This is an issue that can be anything from a non-issue to a major issue depending on the user and configuration.



The only other thing in bold in the please read section is a warning against operating the unit continuously on high for more than 10 minutes to prevent overheating. The unit does get warm very fast on high. After 10 minutes the head is almost too hot to touch. On the medium mode (which has a similar power consumption as the previous generation P7 head), the unit can be run continuously without heat problems in most conditions.



100_4415.jpg




In my samples, the previous generation P7 head was a closer match to SF HA color. The new unit is very light in color and stands out a bit much against the more common darker colors of the SF body parts. Anyone lucky enough to have some of those old Leef C-M bodies would probably be in good shape here for color matching.



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Electrical and Performance Testing:




I rigged up a make-shift lightbox to compare the modes and to compare the new SST-90 unit to the older P7 unit (I have the single mode P7 unit). The lightbox is basically a storage bin with clear sides and a white top and some various paper inside. The white top acts as a diffuser. The comparison should be pretty valid between these 2 lights because they share the same/similar size head/reflector/LED type. As it would turn out, the lux readings are right in the ballpark of what I would estimate the lumen output to be at (pure coincidence). One of those strange coincidences in life and entirely not planned.



Batteries/Host:

3x protected (black label) AW 17670s (relatively new)

M6 w/3x17670 adapter



I did numerous tests with a test bench style setup where I could measure pack voltage and current flow outside of the host. I also tested the operating Vf of the LED and current to the LED with the 3x17670 battery rig.



LED Vf: 3.65V (initial), 3.45V (warm)

Measured current to LED on high: 5.85A

Power to LED (measured on high): ~20W

Power to LED (medium mode, estimated): ~8W

Power to LED (medium mode, estimated): ~1.2W

(Power consumption on low and medium are calculated from other known figures, not measured, I dont have a true RMS AC+DC DMM)



The Power column in the chart below is the total power being consumed from the battery pack (measured).





SST90vsP7.gif




There is an initially higher output when the unit is first fired up in high. The LED is cold and the forward voltage is higher at this time. The difference is shown in the chart above by comparing the initial readings to the after 10 seconds/1 minute readings.



Driver efficiency is bad all around. By my calculations, medium and high modes operate ~70-75% efficiency, low mode ~50-55% efficiency. The older single mode P7 unit makes much better use of electrical energy with a driver operating at ~85% efficiency or better.



Low and medium modes are produced via very high frequency PWM or something of that nature. I can hear a high pitch noise from the unit when operating in these modes if I hold it close enough to my ear or if the room is silent. The PWM is either buffered or just so fast that it doesn't matter, I can not detect any flicker no matter how fast I wave my hand in front of it.



In actual use, the drop in output through those first few seconds is not something you can notice very easily and its probably a very normal phenomena. Since its a smooth transition to a lower output, and the total difference is still within a ballpark that doesnt come close to stretching into logarithmic changes, human eyes just cant detect that a change took place. Since the 1500 lux reading only really happens for the first fraction of a second, I probably shouldnt have bothered even mentioning it in the review, but I thought it would be an interesting topic of discussion.





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Thermal



I never understood why (going back to the P7 unit, which shares it's design with this new unit)... but there are a number of holes drilled in the head that I would think would reduce the effective heat transfer away from the middle of the unit. Makes it look pretty cool with the bezel/reflector removed though...



100_4422.jpg




Interesting eh?



Regardless of whether those holes were there or not, there is simply not enough mass and surface area in the unit to dissipate the heat on high for continuous operation. This is actually a trade-off since it would likely require a head roughly double or better the size/weight to operate continuously. I think a CPU cooler might not be a bad place to look for proper cooling!



Heat transfer to the fins of the sink is working as expected and intended. The fins start to warm up very quickly in operation on high mode. No doubt, the heat is spreading through the unit quickly.





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Final Thoughts:



A perfectly functional unit with plenty of lumens to impress. The shoehorned build introduced a number a problems that really knock off some points.



In actual use, the product is functional and useful if it fits the application. I am not aware of any products that compete to fit this particular niche. Surefire compatible lego opportunities can offer a lot of utility value regardless of how they compete with purpose built products that dont play lego.



Because of the multi-mode and lack of efficiency, I would classify this head as more of a gee-goly item for collectors, enthusiasts, etc. Though it could very well be implemented for a duty based task. I will keep this head in my M6 configuration-options pouch as it could come in handy.



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Beam Shots:

(coming soon)
 
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