[PART 1] Official BLF GT Group Buy thread. Group buy officially closed! Lights shipping.

I think it is the opposite of luminous efficiency. A quick search suggests that about 75% of the input energy as heat would be a reasonable value.

Edit: Texas_Ace beat me to it. But it’s good that we came up with about the same numbers.

Tactical ring on the battery tube has a function as a place for a shoulder strap to attach, and of course that is removable.

cigar-carrying it LOL

fritz15 you're right, here compared to your new design.

fritz15 Congratulations on your design, I know it is not easy to make such a harmonious design. Well done.

and other designers want to thank you for a well done job.

Hi,

I found a lengthy topic on the cpf here: LEDs waste 75% as heat | Candle Power Flashlight Forum
The bottom line seemed to be that you take the maximal theoretical value of 300 Lumens/Watt and divide it by the efficiency of the led. For example for the XHP70:

3249 Lumens at 85 degrees Celcius and 4.8 Ampere and the Vf is 6.3 Volts. So 4.8 A x 6.3 V = 30.24 W
Next, 3249 Lumens/ 30.24 W = 107.4 Lumens/ Watt.

Now dividing the 107.4/300 = 0.358 which leaves us at an efficiency of around 35%.

Here is a thermal analysis with 120 Watts of heat, 20 degrees ambient temperature and a convection coefficient of 27:

Unfortunately I can’t perform an analysis x minutes after applying the heat.

Edit: Wow, awesome thanks 5ar! Well to be fair your design is amazing as well and I am looking forwards to seeing the others, too.

LED’s at their rated levels are indeed generally closer to 35% efficiency.

I have no idea where the 300 lumens per watt comes from or how it plays any role in this?

Although by some numbers for the XHP70 from my own test that is closer to how we would use it:

XHP70 @ ~10A has closer to ~66 lumens per watt, less if driven harder (rough math based on my L6 results, I have not had an XHP70 I wanted to kill for a proper test)

So that puts the final efficiency based on your numbers closer to 22%. Which is about right based on my other research. No idea why though.

You have to remember that we overdrive the heck out of emitters and they generally end up around 50-60 lumens per watt by the time we are done with them, that is unless they pop or “max out” first.

Thanks for the test, it gets nice and toasty for sure!

One thing that is shown is how the fins being below the shelf really reduces the amount of heat they can dissipate. The heat is all concentrated right around the shelf.

Luckily it would be enough for the stock setup, it would just limit the max brightness levels of modded setups.

Click on the image to view full resolution

5ar design v0.6 photorealistic renderings

This is my vision of the BLF GT flashlight I hope you like it.

I accepted your suggestion, and I think we have a pretty design and performing flashlight. Thank you all for your support and advices.

That reminds me, the other designs need to be sure to incorporate the threaded head section thus allowing the head to be made from a smaller hunk of metal saving money and allowing easier access to the LED.

Wow, that’s amazing!

I like it a lot. Which file formats can you export? Maybe I could perform a thermal analysis of your model. It would be interesting to know if it maybe performed better than mine.

The 300 lumens per watt is, as far as I understood it correctly, the maximal theoretical value a white led can reach (wikipedia). At this point the led would have a efficiency close to 1 or 1. Now if a led puts out around 150 lumens per watt it would have half the efficiency of a perfect led and consequently around 0.5.

But you are right, the way leds are driven here they are less efficient. But hey, our numbers agree here so it sounds about right. :+1:

Yeah TA, whatever is chosen needs that two piece head for sure

Oh we are doing Sinterklaas tonight, those things tend to end late so it could be 00-01 o’clock before posting the poll.

My design already has a divided head, see this cross section.

@ 5ar: Why actually the cigar grip ring? Can’t a shoulder strap be attached to the tailcap as well?

Hmm, interesting that it happens to be close but I doubt the 300 lumens per watt is the “perfect led” personally. That claim used to be around 250 lumens per watt IIRC.

Cree has already made a 303 lumen per watt LED and something tells me that LED tech has not maxed out never to be improved again.

The interesting thing is that in a perfect LED with 100% efficiency there would be no heat to get rid of, it would all exit the front of the light carried by the light photons.

The same goes for car engines, if they were to run even 75% (IIRC) efficiency or more they would not need radiators and could be easily cooled by air.

All the latest coatings and tech has sought to bring this about and there is some promising tech out there that could vastly improve things. Although not sure they will ever get THAT good.

Great! just making sure everyone got that memo.

The tactical ring was added as an anti-roll device first and strap attachment point second. Although it does give you options for balancing the light in different ways by having both.

If the tailcap switch is removed then the bottom of the light could be made flat and remove the holes there, so nice the have the ring already designed for a secondary strap point ahead of time.

So as far as I understood it from the cpf topic: Lumen is a unit based on the human eye. So one watt of light in green has more lumens than one watt of light in white. So there are different upper limits for different wavelength types. That’s why cree already cracked the 300 lumens per watt. See this table on wikipedia: Luminous efficacy - Wikipedia

Hmm, I don’t claim to be an expert on the subject at all, I just don’t think we are that close to truly “maxing out” LED tech.

I have never really researched it though so I have nothing hard to go on besides that.

I could very well be wrong and we will have to start looking for new lighting tech in 5 years.

Well, just remember that Cree hit the 300 lm/w efficiency at a very low current. So, of course, there can still be improvements just by making the efficiency go up in higher current scenarios. A “perfect” LED would have to be one that could never burn out at any current. If there’s no heat, how could it? So, there is definitely a long way to go still. :wink:

I still vote for your design fritz. Its really an elegant flashlight.

Sorry, you’re reading that wrong. Luminous efficacy - Wikipedia
100% luminous efficacy is 683lm with 1W.
The theoretical maximum of an LED is 260-300 which it says right beside is 38.1–43.9 efficiency.

Driving an XHP70 at 12A requires 7.5v, which is 12*7.5=90W. At this current it produces slightly over 5000lm, so you get 5000/90 = 55.6lm/W
If you look on the wikipedia page, in the first chart, 54.7lm/W is 8% efficiency. So basically for the XHP70 7.2W are turning into light, and 82.8W are going into heat.

No, the 683lm are for 555 nm. For a different wavelength this value is lower.

It says for an LED that 300lm is 43.9% efficiency.
300/0.439 = 683.4lm
So that means an LED working at peak efficiency 300lm/W will only be converting 43.9% of the power into light.

I quote the first sentence in the wikipedia article

So for green the Luminous efficacy is 100%. That means we see green light best. However, we don’t see other wavelengths as good as green. So what we perceive as 683 lm in green, we just perceive as around 300 lm in a different wavelength.