Tail standing with a fan on it i’m pretty sure mine could have held turbo till the battery was empty. I didn’t let it go that long but it seemed fine. Who knows what that means in the real world but it has Narsil so you can bump up the temp if you dont mind it getting hot.
Since the driver is an FET driver, it will only see peak current for a minute at best, after that the current is dropping so the risk tot he LED is dropping as well. If it survives the first minute or 2, it should survive longer term use. The issue at that point becomes total heat buildup, which is another problem entirely.
It does not tell you how well it will handle long term usage though, as in months/years using it with freshly charged batteries.
Maybe a dumb question! so does that mean as a current drops the output drops? So after one minute wil the output constantly be dropping? I wonder how much of a drop it is after 5 minutes?
I guess if I notice it by eye,I just bump it back up the turbo again or will that not make any difference?
I’m at the driver license center it is mobbed in here!!
Thanks
yes, always dropping. However, most of your VN lights were probably FET too. So it should be nothing new for you
edit: and this also means there is no “bumping back up” unless the reduction was due to temperature
So it gives you Max output for a minute or two and that’s it.?
As long as the output decreases very slow rate and it’s not noticeable by eye, It really won’t matter.
and for any Light I guess once you turn it on its constantly decreasing in output and I’m sure it would be 54 lights are the same
Several of them I cannot notice the difference between minute 1 and minute 20.
tn42 v90 seems just as bright at turn on as it does 25 minutes when the batteries are almost exhausted.
Using voice activation …bad Grammar!!
Yeah, you will not notice the output drop in most cases since it is so slow. As was said many lights you already own are most likely FET already and you did not even know it. You only really notice it if you look for it.
It takes a 4x change in output for your eyes to notice a 2x change. So even fairly large drops in output get completely missed by the eye.
The NARSIL has a feature where I can[and will] disable the step down. Does that really mean anything if the light will be constantly decreasing in output anyway?
Yes. Just set the temp real high in your case (instead of disabling) since you don’t mind burning your hands 
That way it may continue to run uncomfortably hot but still be able to step down should it get to a point where it could be damaged (like in the summer time)
lol!!!.
I am always full of questions!
Does it have a timed and thermal step down? I sacrifice a little pain[red hand] for the enjoyment of turbo!
Disabling the step down sound like a better idea,my hands will be the judge as to when I turn it down! :sunglasses:
These are 2 very different tests. Measuring lumens is like measuring an engines horsepower. Measuring run time is like a cars top speed. They are very different tests.
A FET driver is often called “direct drive”. When you activate turbo it’s kinda like connecting the battery to the led directly. As the battery drains, the led gets less power and it can be hard to see with your eyes. It’s easily measured, though.
Think of it like an old style incandescent flashlight with an on/off switch. You put in some fresh alkaline batteries, turn it on and it will be bright for a long time. In actuality it’s brightest in the first minutes by a little bit, but you can’t really tell by eye. As the batteries drain, the bulb gets dimmer. So output gently slopes down.
So due to this “direct connection”, a FET driver gives the highest output of all driver designs (generally speaking). It’s also why the battery has such a big impact on its performance.
NarsilM has both timed and temperature stepdowns. Temperature based should be default.
The thermal stepdown is mainly there to prevent people from burning themselves. It’s a safety thing.
The drivers and leds can usually handle way more temperature than out hands can. It varies from light to light, though. Certain leds can take more temperature than others. Certain flashlights can shed more heat than others. Certain drivers can deliver more amps than others.
Turning the thermal stepdown off is fine as long as you accept the risks.
My L6 has no thermal stepdown and it pulls 19 amps on the 70.2 led. That’s like 120 watts. I just use my hand to know when to turn down the brightness a little.
Might be too late but still posting to show interest 
You missed my point.
I’ll explain again. Doing an ANSI test is NOT like a real life test, a torture test if you will. 30 seconds will NOT put the LED or the torch through the stress of Continuous Turbo/Max output. That was my point.
Honestly, when you quote me,a lot of times you are giving me basic information unrelated to the subject matter,it can be irritating. 
I must not understand your points.
Why say the tests are different? We know this. You make it sound like you expected them to be related. This confuses me.
Sorry.
You are definitely confused!
We are trying to figure out if the 21700 will be detrimental to the SST-40 LED. TOO many amps?? I think djozz witnessed Two SST-40 LEDS dying from too much current.Something like over 9.8amps[not sure of exact number]
Several guys who were the first to get this light tested it w/ 30T/40T/P42A. They did the 30 second ANSI test and said the batteries did no harm and that they also so no additional output. Not ONE of them said they used the light for extensive periods of time on turbo with those batteries.21700 is NOT proven for long term use,that is what I am still waiting to hear and wondering!
I think it is safe to say that using a light for 30 seconds is NOT as hard on the LED as using it for 5, 10 minutes straight on turbo, and then continuing to do that.
I was simply saying a 30 second test is not a good indicator compared to LONG term turbo use and the stress it can put on the LED that is supposedly susceptible to frying at higher currents.
30 seconds to me does not seem like a good barometer of long term affect of high amps on an LED.
No other way that I can say it,basically said it the same way a few times!
No one can tell you long term how it will hold up in your $30 light. Worst case is the fix costs only $5 to replace the LED years down the line.
As far as battery choice you seriously are overthinking it. Dont buy more batteries if you have the 26650’s especially before you even get the light. You are getting too excited and ahead of yourself over nothing.
This difference at 7A is not perceptable, even at 10A you wont “see” the difference without using a meter and I think we are safe to say this isn’t pulling 10A stock. Stick with what you have and enjoy the light. I’m pretty sure based on your posts you will like this light. The light is a very good thrower stock and handles turbo well.
Perhaps the best advice would be to browse this (very long) thread, as much discussion has revolved around batteries. EDIT: see above posts, which were posted as I wrote this.
Basically, this is a ~9A light with the best cells available. Most people here know more about batteries than I, but many 26650 and 21700 cells are suitable. Shockli’s 5500mAh is probably the best compromise between capacity and performance, but it can be difficult to find and shipping charges may cost more than the cell itself.
If genuine, the LiitoKala 5000mAh is a good value cell and will provide high capacity with only slightly lower performance than the Shockli.
Some people have tested with a 21700 Samsung 40T. There remains concern that a high-drain cell could be pushing the emitter quite hard, but I don’t think anyone has reported damage to their FT03. More testing is probably needed as we don’t yet understand how long this emitter can handle such high currents. For now, it’s probably healthier for the light to use a 26650.
With a high-drain 21700, you are trading a lot of runtime (and possibly emitter lifespan) for an initial period of higher output, so the choice depends upon how you will use the light. Most people recharge often, much like a smartphone, and thus don’t care much about long runtimes. With 5000mAh cells, most of that runtime will provide reduced, but still useful, output.
As is often the case, there are numerous rebranded versions of all these cells. Many batteries can be compared HERE. It doesn’t include all brands and it can be confusing to determine which cell is under whose wrapper, but any quality 21700 or 26650 should work well in this light. 18650’s will work, but most will not provide maximum output.
Yes,I see what your saying sir.I analyzed ALL the graphs…30T/40T is slightly better in the beginning of Voltage curve than the P42A!
I do not expect to notice 185/215 additional lumens by eye. However, it is a psychological advantage when your getting 185 to 215 more lumens!
Number from “Flashaholics” taken from my Post # 1844
ALL ANSI numbers:MAX Ramp
Shockli 26650 5500mAh=1040L
Amps plus 18650=1138L
30T 21700=1265L
ALL ANSI numbers:TURBO
Shockli 26650 5500mAH=1814L
Amps Plus 18650=1895L
30T 21700=2000L
I understand your point sir,I am NOT buying more 21700[I returned the P42A!!!] UNLESS my secret Modder suggests it after I most likely get it modded,de dome, current boost. :sunglasses:
@wolfdog
Performing an Ansi Turbo test on a FET driven light is very valuable to your question of whether or not continuous use of a certain cell can damage the light. If the light survived for 30 seconds on turbo with a particular cell after 5:00 minutes of turbo the cell would likely already be depleted to around ~75% which directly correlates to the maximum output at that time (~75%)
It should only take less than a minute on turbo with a FET driven light to nullify any power advantages of different cells