lights with single 18650 cells - turbo mode question

Hi all, after some good advice here and buying the Fenix E12 I think I have caught "the problem". I want more....

I was looking at some of the rechargeable 18650 options and the fenix uc35 looks pretty decent. What I was wondering, with all the single 18650 cell lights is do the turbo modes work when the cell is partially depleted. For example a lot of the lights step down after a few mins, but one like the thrunite p12 get gradually dimer according to selfbuilts graphs. So would I lose out on the highest modes shortly after some charge has been lost, or is it simply" thermal management " and I will be good to go again once the light cools down?

PS not sure where this would be most appropriate here or the battery sub forum sorry

Thanks in advance

Kel

The step-down from turbo mode is temperature based. They don't want the light damaging itself or hurting the user from the high temperatures of the LED working so hard. For example, a CREE XM-L2 will get to 85 degrees Celsius/185 degrees Fahrenheit which is quite hot. To answer your question: you will lose the turbo once it automatically steps down to high, and if the light is programmed to step down once more, it will. You can override that step down by switching back to turbo manually, but you risk damaging the light.

The turbo modes and subsequently lower modes will all eventually get lost as the battery loses charge. The light physically won't be able to power those modes because there isn't enough energy in the battery to do so. Most lights, unless proven to gradually dim by people like selfbuilt, should hold a constant brightness until either the mode is manually changed, or the step-down process happens.

Just to add, it would be rare to find a truly high output single 18650 that didn't decrease brightness of turbo over time. In other words, a constant 900 lumen output for a total runtime of an hour I have yet to find.

Rob

900 lumens produces HEAT! I love small bright 18650 lights. they all get hot pretty quick. 5 mins or so.

The step-down on most designs is for thermal reasons, but usually is time-based.
But what I think you're alluding to: yes, with most 1x18650 lights like the UC35, once the cell partially discharged the brightness of turbo will start slowly dropping. This is not so bad however, since you can't really detect much of a difference until it's dropped more than ~30% (and then only faintly). After a while the difference between turbo and the next mode would fade.
If these lights were fully regulated at ~1000 lumen, their runtime would be significantly shorter. By the time you would notice the difference a fully regulated light would have run out (look at the Armytek Predator Pro and Viking Pro tests by selfbuilt, compare Fully-regulated to Semi-regulated (have a Predator Pro v2.5 NW on the way and am living in heavenly excitement / agonising impatience about it))
I think the regulated runtime most designs can manage on a 3400mAh 18650 is around ~15 min, I estimate, I have yet to produce some reliable runtime tests. Selfbuilts old 18650 were 2200mAh which have bad time delivering power for high power flashlights.

somemoregear said:

You can override that step down by switching back to turbo manually, but you risk damaging the light.

Click to expand...

This is highly unlikely.

Scourie said:

Just to add, it would be rare to find a truly high output single 18650 that didn't decrease brightness of turbo over time. In other words, a constant 900 lumen output for a total runtime of an hour I have yet to find.

Rob

Click to expand...

Heat is certainly an issue. But that is not the reason you don't get 900 lumens for an hour. It's simply the battery and driver cannot support this level of out put for this duration.

Most small 1x18650 lights will use a linear driver. As soon as the battery voltage drops below 'x' you will loose regulation. You would need a boost driver and a good battery to maintain output at lower battery levels.

KelDG said:

Hi all, after some good advice here and buying the Fenix E12 I think I have caught "the problem". I want more....

I was looking at some of the rechargeable 18650 options and the fenix uc35 looks pretty decent. What I was wondering, with all the single 18650 cell lights is do the turbo modes work when the cell is partially depleted. For example a lot of the lights step down after a few mins, but one like the thrunite p12 get gradually dimer according to selfbuilts graphs. So would I lose out on the highest modes shortly after some charge has been lost, or is it simply" thermal management " and I will be good to go again once the light cools down?

PS not sure where this would be most appropriate here or the battery sub forum sorry

Thanks in advance

Kel

Click to expand...

Nobody has really answered this question.

The answer is, you won't likely loose the turbo mode, but the amount of light it produces may not be a noticeable difference from the next mode down once the battery gets low.

It also depends on how the Turbo mode works, if it's just an amp hike and still regulated, or as with the case of many modern lights if it goes Direct Drive in turbo mode (non regulated).

If you use Turbo and high outputs mostly, then a high performance battery will give you better sustained performance. However runtime will be lower as you are simply consuming the available energy more quickly.

Chicken Drumstick said:

Nobody has really answered this question.

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I did.

Also, flashlights haven't used linear drivers for a long time. Most employ a buck driver, same as boost but drops voltage, without much loss.

Thanks all, so basically turbo modes will be available on a partially discharged cell but probably not be as bright as a fully charged cell, once past a certain point the mode will be no different than the next mode down.

I'm trying to decide between a 4aa and an 18650 you see, the 4aa seem to put out the higher modes without stepping down for a longer time but I really like the form factor of the single 18650s (multi 18650 worries me)

KelDG said:

Thanks all, so basically turbo modes will be available on a partially discharged cell but probably not be as bright as a fully charged cell, once past a certain point the mode will be no different than the next mode down.

I'm trying to decide between a 4aa and an 18650 you see, the 4aa seem to put out the higher modes without stepping down for a longer time but I really like the form factor of the single 18650s (multi 18650 worries me)

Click to expand...

4xAA won't loose intensity (aside form timed step down) as the cells discharge because the cumulative voltage is hight enough, with 1x18650 it's high enough only when the cells are fresh. The step down on 4xAA designs tend to be longer as the flashlight is more bulky and can absorb the heat better.
While you won't kill your flashlight by continuously bumping it back up to turbo, it will get uncomfortably hot and may shorten the lifespan in the long run (compare to the redline of a car, once won't hurt, but for a 100 miles it will).

I would advice 1x18650. While you might not EDC it, it would still be small enough to take with you when you know you're gonna need it, without obstructing you.

Yeah I am worried the 4aa is to big and will end up being left at home, think I have narrowed down the 18650s to the Fenix uc35 (con is that it is 150mm long but has fantastic mode spacing) vs the olight s30r ( con is the awful mode spacing hi 600 med100 what's that all about but it is so compact). I really like the idea of the rechargeable lights that use a non-propriety cell.

TheBelgian said:

I did.

Also, flashlights haven't used linear drivers for a long time. Most employ a buck driver, same as boost but drops voltage, without much loss.

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Plenty of lights use linear drivers. In fact the only buck driver torches I own are multi li-ion ones. Buck isn't needed for single li-ion as you can direct drive most leds without the need for a driver.

KelDG said:

Thanks all, so basically turbo modes will be available on a partially discharged cell but probably not be as bright as a fully charged cell, once past a certain point the mode will be no different than the next mode down.

I'm trying to decide between a 4aa and an 18650 you see, the 4aa seem to put out the higher modes without stepping down for a longer time but I really like the form factor of the single 18650s (multi 18650 worries me)

Click to expand...

while the 4AA approach does give a higher voltage. Alkaline batteries are really no good for it. You'll most likely want NiMh. So the voltage increase over a li-ion is only marginal. The AA's are also likely to suffer higher voltage sag. And of course NiMh is only going to offer 2000-2500mah where as li-ion is 2500-3400mah.

To sum up 18650 lights usually out perform the AA ones. In max output, runtime and regulated output.

Chicken Drumstick said:

while the 4AA approach does give a higher voltage. Alkaline batteries are really no good for it. You'll most likely want NiMh. So the voltage increase over a li-ion is only marginal. The AA's are also likely to suffer higher voltage sag. And of course NiMh is only going to offer 2000-2500mah where as li-ion is 2500-3400mah.

To sum up 18650 lights usually out perform the AA ones. In max output, runtime and regulated output.

Click to expand...

Cheers, I would be using eneloops for a stack of them now, cracking little batteries.

Selfbuilt reviewed the Thrunite 1A V2 2014.

He played around with this idea at the behest of a post.

In this one particular light it did restart back at full brightness.
The light has a really good circuit that is not typical.

Nothing scientific, but I have five or six high end 1000 +/_ lm lights. The PD 35 outperforms them all. I just got a nice leather holster for it and carry it all the time. Just my two cents.

Jack

+1 for the UC35. It is awesome and you can charge any 18650 you want in it precisely. Built like a tank, near perfect ergos and impressive heat sinking. Well spaced modes, greatly improved side switch with low voltage LED indicator underneath, one of the best tail switches there is and of course the unmatched wall of light(except the PD35 of course)it puts out is far more usable EDC wise vs the non Fenix competition.

Having a pd35 and love it,i +1 to the above and would not hesitate with the usb version uc35 to fit in with your requirements.

May get one as well myself for added convenience,may even be a car edc(or edd,every day drive) light! .............:thumbsup:

Just put in a modded driver with no rampdown. You'll know turbo mode has been on too long when:

1. It turned on in your pocket and your pants catch on fire.
2. You get 3rd degree burns from ultra-hot aluminum casing.
3. The battery melts and the light explodes.

:devil: