Interesting way to do it
With 10 Watt COBs? Talk about total flood and no throw whatsoever! (except brute force from the “4000 lumens” output)
I like it, simply a resistor in series with the leds, heat is divided over 4 leds. I just doubt since there is no fan on the heatsink if it can dissipate the 40W over time. But for short runs it will be fine.
1. Real power of this COBs is about 6W
2. Real effincy is about 50lm/w. 4*6*50=1200lm (CRI is lower than 70)
3. There is no way to focus this lumens, only 180 degrees throw.
If anyone is going to repeat this I highly recommend to use normal cree/samsung/lg leds (3535 size) on triple board. They are cheap enough, have much better effincy and can be used focused up to 15-20 degrees.
Or go proper and use 4x true 50W COBS and keep the fan on the CPU-cooler.
This is a very clever build, I like it.
I am not trying to trash it, the build is good, but we all know how hard it is to produce the claimed 4000 Lumens.
I assume that number comes from the claimed lumen output of these Chinese COB emiiters. First off, that’s not true
In addition to that, 3S fully LiPo’s charged is at MOST 12.6V. IF these emitters drew 40W, then from ohms law etc, I=P/E.
In this case I = 40/12.6 = 3.16A. BUT there is a 1 ohm resistor in series here, so that resister would drop I x R volts or 3.16V
That means on startup with the LiPo pack putting out at the VERY best 12.6V, the LED’s would see at best 8.84V.
At that voltage the LED’s would draw no where near 3A. And of course things would get worse from there.
I am going to guess around 1000 Lumens here, maybe even less.
Pretty impressive for what appears to be a 14 year old judging from his voice.
Hm. Where can I go to the local copy shop and run something off on a 3D printer?
Do a quick search online for your area. There’s probably a 3D print service around.
Have you seen this: 1000W LED Flashlight - Worlds Brightest (90,000 Lumens) - YouTube ? 10x 100W COBs 
Horrible efficiency and probably nowhere near claimed 90k lm, especially when warm, but still plenty of light.
I bought a 3D printer for $139 + $50~ shipping (from Banggood called the A8 [clone/derivative of the Anet A8 running the Anet V1 controller board]), price has gone up though, but it print’s great.
I just though you guys would get a kick out of a kid making a pretty powerful light from scrach, kid has alot of stuff on his youtube channel