Fireflies E07 preview

D4S also more surface area than D4. Extra mass will only add like 20 seconds to turbo runtime, what you’re really after for heat dissipation is surface area. The 7x emitters will have a very high turbo output yes, but what the sweet spot here is more efficient lower outputs. It won’t be able to maintain 1000 high cri lumens with perfect regulation like the ROT66, but probably more along the lines of 400.

With a 1.5” head, I think it will be too big for pocket carry anyways outside of cargo pants and/or jackets, so a slightly chunkier body probably wouldn’t hurt, but I wouldn’t want to make it too bulky and/or sacrifice usb charging.

Please describe the heating difference in detail Sofirn C8F(18650 or 21700?) and D4S.

I like the adding mass idea. And i agree that surface area is also important. I built a heat exchanger gadget to cool my laser and to create more surface area all i had to do was add more cuts in the aluminum. I was working with 1/2” Al, stock and what occurred to me as i was fabricating, was that each cut i made added surface area —more access to air to remove heat. If i just kept the 1/2” x 2” x 4” block i would have roughly 22” of surface area, but if i made a cut perpendicular to the 4” side i add roughly 1 7/8” of surface area per kerf/ slice.

So, for my gadget, the aluminum absorbs heat from water thru copper tubing and a fan runs blowing air thru all the nooks and crannies removing heat. Note: i have no scientific evidence to support this hypothesis, just gut and instinct. I think i am right—but i dont know for sure.

Point is, i suspect the 4 or so fins they have milled in the prototype picture may be increased to effectively double and triple +, the surface area—more contact area with air, less heat. Also, i think i found information suggesting copper was a better conductor of heat. And depending on alloying of the Al, the copper seems stouter than the aluminum in my opinion.

I would add a picture to show what i built, but dont see a way to attach local files, from my phone.

Nice!! Interested!!

I just took some lumen measurements at 1s -> 30s -> 60s
D4 XP-L HI 5D (62.8g) : 3,310 -> 1,009 -> 250
D4S XP-L HI 5D (142.2g) : 3,577 -> 3,210 -> 2,670
C8F 18650 (195.2g): 3,170 -> 2,870 -> 2,820
Measured weights exclude battery

The feathery weight of the D4 obviously perform much worst than the other two, while the C8F is the most stable. At 60s, the C8F feels the coolest to the touch by FAR. Also although I agree surface area is important to allow heat to convect into the air, it is really only important for sustaining lower output. For sustaining turbo output, heat sheds way too slowly through convection compared to the heat gain, therefore we have to rely primarily on mass to absorb the heat to extend turbo run times. Also even if you increase surface area by adding fins, it will not really speed up heat loss through convection very much under still air. I remember seeing turbo runtime data of the D4 copper head vs aluminum head that shows the output is maintained much better with the heavier copper head.

C8F has the best design for handling heat from high output. The majority of the mass (74.2%) is in the head. The size and surface area of the head of C8F and D4S is similar. However, C8F head weighs 144.8g while the D4S head weighs only 75.0g. This is why the C8F head feels mildly warm after 60s whereas the D4S feels much warmer.

This is the reason why I am concerned about the light weight of the E07 because with 7 emitters pushed by high amp 30T cells, it can create much more heat than the D4S and C8F. Hopefully Fireflies can add more weight into the head, such as by thickening the shelf for the mcpcb. Will not add much to the cost but greatly improve performance.

Nicely done. Scienced the s#!t out of that.

D4: 16g/emitter
D4S: 35g/emitter
C8F: 65s/emitter
E07: 20g/emitter
E07+40g: 25g/emitter
A major weight increase that you propose won’t bring it anywhere near C8F in Turbo time. If stock D4 has 10s turbo, E07 has 12.5 and E07+40 has 15.5.

That’s not perfectly correct, head weights matter more than full lights. And E07 even with 30T will drive its emitters less hard than the others.

But anyway: unless the light has a lot of resistance this will be a D4-style hotrod and extra weight won’t change that. If you don’t like it, it’s probably not the light for you.
D4 was a very divisive light. For many it was the light of the year. But it received lots of criticism for what it was - the hottest hotrod out there. I believe E07 will receive a lot of sympathy from those who loved D4. And lots of hate from those who didn’t.

Fireflies could have made it with 4 LEDs, there are suitable lenses available at about the same diameter. The light would become like 2 mm longer and much cooler. But I guess being much cooler was not the point.

Why I asked you, my research C8F (18650) at an air temperature of 24C grieved me:

- in 990Lm mode. After 20 minutes, the head temperature reached 58 degrees.

  • in 650Lm mode. After 25 minutes, the head temperature reached 54 degrees.
    I think the design lacks cooling fins and more. In version 21700, added cooling fins, but I think need more.
    It was interesting to compare with other studies. And I wonder how the Fireflies E07 will show

TBH, I’d be just as happy with this using 3 emitters, 4, 5, 6, or 7. As long as it has decent performance at ~1000 lm and below, the brighter modes are mostly just a bonus. I’d rather have less weight instead of more turbo.

If it ships with Anduril, it’ll have a relatively sane ceiling by default, which should help a lot with not overheating. But turbo is still there for quick bursts.

Clip pushed onto body is a big NO.
Solarforce style is much better.
Mike

sp5it, that’s a good point. I also prefer a captive clip which cannot slip off the light. However, I have found the Olight S-Mini clip works pretty well, despite being a clip-on clip.

What I’d ideally look for is a deep-carry clip which extends almost to the end of the light. This shape works really well:

But on this light, instead of having two arms which clip on, it’d probably be best to make the clip thread in. And it’d be bezel-down, of course.

The Oveready universal clip shows the captive design nicely. I would mostly just modify it for deep carry:

… but not too deep. :smiley:

Slip off and scratches when put-remove clip a few times.
Mike

Unfortunately, added mass doesn’t allow it to shed heat faster. It is useful for maintaining high “steady” output longer. For example, I have eight Convoy S2+ hosts (6 aluminum and 2 copper) that I’ve been using/experimenting with them by tail standing as room lighting on nightly basis for several months a while ago. Using the same pill at the same output mode in a much heavier copper Convoy S2+ host vs the standard aluminum versions, the copper host takes about 3 times as long (seat of the pants estimate… not going to spend time to swap out the pills to stop watch it) to raise to unbearable temperatures and also takes much longer to cool down. So adding mass doesn’t really increase the max sustained output running indefinitely, but being able to use the same mode for 30 minutes instead of 10 minutes to me greatly increases the practicality of the light.

To control the temp under low-mid output modes running indefinitely, we need more surface area to radiate heat, and also air movement to convect heat away. Still indoor air won’t do much good. However, adding a couple of fins won’t do much to extend turbo runtimes because the heat gain is so much faster than heat loss through radiation and convection.

Also the Sofirn C8F driver was designed for high output and I suspect is not very efficient. With an efficient driver, I think the host can likely maintain 1,000 lumens comfortably for 30+ minutes. Even the 90CRI T050R emitters, with less surface area than the C8F and weigh only 126g can maintain 820 lumens in room temp without active cooling as tested by Maukka. However, the TO50R has far higher efficacy than most flashlights. Maukka tested the TO50R at 125 lm/w at 250 lm compared to the ROT66 at 79 lm/w at 100 lm.

Where did you pull these numbers from? To me these are completely baseless and is misleading for those unaware. I suspect turbo is designed to last 30s on the E07 as is. By adding 40g to the head as I suggested, it will last much longer. Adding 40g to the head of the E07 is almost doubling the mass and should be close to 100+ g and will allow turbo runtime to increase much more than 3 sec while brightness decreases much slower.

I just tested my C8F again and at 2 minutes, it only dropped to 2,680 lumens but for some reason abruptly dropped from 2,670 lumens to 70 lumens at 2.5 minutes (timed step down or defect?). However, the head was still comfortably warm at 2.5 min.

Because E07 has 7 emitters, the current will be spread among the emitter so each emitter would be pushed less than a 4 or 3 emitter light under the same setup. However, this doesn’t change the fact that a 30T battery is capable of pumping much more power (watts) than a 30Q in a C8F.

I understand some people like yourself do not need the light to be practical and do not care about having stable output for longer periods. I also understand some never use their lights over a couple hundred lumens but there are much smaller lights for that. However, there are also some people who prefer a Turbo that last much longer than the 20sec on the D4. I actually use my lights for work purposes illuminating large interior spaces and I see this light to have the potential to replace my TC20, which can maintain about 1,000-1,200 lumens and is the current best for its size. I also own 3 D4 and only use them as toy lights because I can’t find any practical application for them.

FF already have a 4 LED light, which is the PL47, which is basically a D4 headlamp, that I already have two on order. I don’t see a point for FF to make another quad given there’s already the D4, D4S, EC65, TO46R, and TO50R that fulfills all needs from hotrod toy to practical light.

A few examples of fins done right to increase the surface area :
Eagle Eye X6 // Skilhunt H03 // 4Sevens maelstrom X7 // Sunwayman V10R (secure and removable deep-pocket-carry-clip done right)

No need to make a bigger head when the surface area of thermal exchange is already bigger with fins done properly.

My favorite is the TR-J20. The massive finned head on this thing can probably handle 10k+ lumens continuous if using an efficient driver and leds.

I also love the massive fins on the Olight SR90. Hoping they release an updated version with modern LEDs and drivers.

Did you configure the Emisar’s for max temperature?

I agree with SKV89 that increasing the head mass will improve the turbo runtime, and it’s really useful. I don’t know how much it’ll improve but comparing my D4 and D4S, both set to max temp, the difference is indeed big. Further, for me it won’t make a difference in EDC so better safe than sorry.

E07 look well but for me 25 degree is not option. I have no where to use. it would be nice to have a spare option of 15 degree.
also samsung leds!

By milling deep fins, the thermal transfer by convection is increased while the mass is reduced. :wink:

I never configured the temp but it gets burning hot. Max temp is probably set higher than on my D4s.