Like other lights of comparable size (think S2+) D4 can sustain about 1000 lumen without breaking, but it will be way too hot to touch then. I can confirm CRX’s test that between 500 and 600 lumen and hand-cooled it is sustainable. When outside with airflow all flashlights can run brighter without overheating.
Charles Lin, Efest makes a dark purple 18500 1000mAh cell that’s high discharge… it gives me some 3400 lumens on my scratch built Ti/Cu Quad and 3200 lumens in my Mec-Army P16 Quad.
Remember that the temperature regulation works differently on different batteries. The VTC6 for example gets so hot so fast that the regulation corrects it much more than on the Aspire for example.
Here’s both cells on turbo with the temp limit set manually to 43°C.
Sampled every 1/3 second. I’ll overlay output on those tomorrow.
On video, without temperature calibration (subtract 3°C):
VTC6
Aspire
Always a great pleasure to read your interesting and well-presented data, maukka! 
Awesome vids maukka, you are da man :+1:
Another night, another walk, another couple of notes:
- If I have the light off, with some low mode memorized. 2-click to turbo. 1-click to turn off. 1-click to turn on. Result? It forgot the low mode and starts with Turbo. That’s unnecessary, if I want turbo again, I can 2-click again.
- I have a light on some high mode, want much less. Solution? Twist the tail cap back and forth, turn the light on. Result? Nothing happens. You need to wait until it double blinks and then wait some more until you can turn it on.
- It would be more noob-friendly to blink out battery capacity (scale 1-10) rather than voltage. Could be slightly off with 4.35V batteries, but there are few of them…
- Thermal regulation really dims it down. It’s way below 350 mA after turbo and takes very long to recover. It’s better to reset it to 350 mA than wait. That’s 219c/VTC6.
+1
I’m no expert here but have a few lights of all size and although i may have not argued as clearly as djozz, i would have said that this kind of small light should not run much higher then 600 lumens because of heat dissipation - as of today. The 3k/4k lumens extravaganza is just that, a quick burst if need be but only for a few seconds. No magic involved here.
Now, hopefully, one day in the not too distant future… we may have more efficient leds that produce very little heat… and this kind of minor miracle may last much longer then we dare imagine. Pure light, no heat, that would be intense. Could you have imagined a D4 just five years ago? Can’t wait to be ten years older! :smiling_imp:
- The year 2027 -
“Wow, I can’t believe this EDC light steps down to 10000 lumens only after 10 minutes…”
imo No, because the light already has built in protection, read post #1:
About 30 seconds at which point the light drops to 10% output…
Look at the post below by CRX… it depends partly on what thermal regulation setting is being used
See post 958 below, to get some idea. It has been suggested that 600 lumens might hold steady. afaikt there is no way to set the light to 600 lumens, or any other specific lumen level, unless you have a light meter.
you Can set to a NoPWM mode of about 150 lumens:
Post #1
Post #958
Thanks for the videos.
Would be great to see the lumen ouput overlaid on these graphs also :+1:
Hmm… So, if you start at a lower level, what is the highest output it can sustain for a couple minutes? 600 Lumens sounds low? So after two minutes my Zebralight SC600 II would be brighter? I see H2 on the Zebra is about 670 listed output, so maybe around that level?
Yes, I know Efest 18500. However, compared to 18650 vtc6/30q/GA & 18350 Aspire; I expect a good 18500 size battery will do High Discharge: 10~15A, Capacity: 1300~1500 mAh.
The link works on my side…….Try copy & paste
Agro, all your notes are confusing.
If you have implementation ideas perhaps you should just offer new code, maybe then a simple reflash would allow others to sample your idea of perfection?
I know several here have already done due diligence to get the D4 to where it is today, I like mine and will be the first to admit I’m still playing with it and learning.
20 amps running through this small light body, in the palm of my hand… Should i be worried?
How much of a magnetic field would that produce? Would it affect a compass up close?… How about PWM induced field variations?
Could you explain what do you find confusing about them?
I would be very happy to do it. Typically these are not major changes. But I have no hardware to be able to reflash the light myself, so I can’t check my changes.
They did amazing work. But there are (mostly trival) wrinkles here and there and I do what I can to smooth them out - give feedback to the makers.
Maukka, are you using the 219c for your tests?
If you are, do you have any explanation why mine steps down in under ten seconds using the vtc6 and lower ambient temperature than you? Should I check if the thermal paste is badly applied on mine?
Btw, I haven’t fiddled with the temperature limit, so it’s still at 45 degrees.
Just did a little test underwhile browsing BLF. I put a fresh 30Q cell in my D4 and using my sphere I set the output at 550 lumen (my D4 now has 3500K 90CRI 219C’s so it is comparable to the stock 219C’s at about 600 lumen). I started hand-cooling the light. I must say I had a rough time, I had to swap hands every minute and it was still an unpleasant temperature, but it really was sustainable, after 12 minutes I decided that I could just go on like that and stopped the test. The output had dropped to 500 lumen then.
I did it again (start at 550 lumen) with a more depleted 30Q (3.7 V at start) and now it was a bit easier, but not much.
So yes, 600 lumen as the maximum sustainable temperature inside at room temperature seems about right. But without hand-cooling it will be lower (TK’s temperature feedback makes it about 300/400 lumen, as read in CRX’s data)
Excellent test Djozz,
But what does it tell us?
Would the D4 be “improved” if:
It were 4 - x mm longer and had a heavy shelf behind the emitter? (would a longer light be a problem?)
Is this telling us that this light is a great candidate for real cooling fins?
Not an expert here but are there other drives that can run the light with less heat (or brighter for the same heat) thermal efficiency?
I understand the meteor m43 has a more efficient driver arrangement, could something like that be a “good” option for the D4?
And My personal soap box, I say we need a “just right” sized light between the 4x18650 MeteorM43 and the 16340-18650 D4.
I’m thinking 26650 with 6-9 emitters. How much meat and fins and with what type of driver should it be specked with?
Please chime in!
How about 3x18650 with 7 emitters? :smiling_imp:
Sounds like you’re describing DQG Tiny 26650 III… 2,500 lumen on turbo, and it’ll run at 900 lumen all day long.