Thanks for the input! Have to try that. I don’t have a 4s LiPo, nor a 4s balanced charger, so I’ll have to see if the local hobby store has any in stock…
The one thing you can do is build up a 6S battery pack if the buck converter supports up.
You can do this just by connecting up 2 3S battery packs in series 
Hmmm… The buck converter supports up to 40V input… I do have two 2s LiPo batteries but they don’t have XT60 connector so I’d have to hobble up an adapter to use those. Will try the hobby store tomorrow…
A buck driver should have no problem running off a 3S battery to buck down to 3V.
The issue is that that regulator can’t handle more than ~8 amps, you need something more powerful.
https://www.amazon.com/Yeeco-Converter-Regulator-Transformer-Inverter/dp/B011UBLZK6/ref=sr_1_6?ie=UTF8&qid=1548202313&sr=8-6&keywords=buck+converter
You can see it says that it’s 8 amps max.
I’ve taken it to over 9 and the converter seems to have no problem with it. It’s that I cannot raise the voltage up any more. It’s rated at 120W, so I should be able to get 5V no?
You can’t up the current anymore because the voltage is starting to be a bit too low.
If you want something a bit overkill, I would actually recommend this monster:
https://www.ebay.com/itm/DC-DC-Converter-20A-300W-Step-Up-Step-Down-Buck-Boost-Power-Adjustable-Charger/392164184788
I’ve bought it myself, and it does work up to 15A passively.
I would not run it at higher levels without higher input voltage above say 18V and actively cooling it.
Still, if you want to push the 2mm2 LED to say 10A, you can, but you will need the best heatsinking possible, high clamping force, and perhaps, liquid metal for maximum performance
The one I have is rated to 12A max with cooling… at least according to this which I copied off Amazon when I bought the thing:
Admittedly, the air leaving the fan is warm, but the heatsink of the buck does not feel like it’s getting hot at all.
Yep.
You need even higher voltages. These cheap buck modules really like having a lot of headroom to push current.
One example would be one of these inexpensive 5A buck converters.
The IC can actually go up to 7A, so put an additional copper shim and aluminium heatsink on it, and boosted the power up to 5,5A.
Put it a 120mm fan across it, and went up to 6A without throttling. Any higher than 6,05A and it would throttle down.
Then, I decided to up the input voltage from 12V to 24V. It could now sustain 6,75A, and handle peaks of 7A for short periods of time.
Thanks… I’ll pick up a 4s LiPo and charger today some time and redo the test. If that doesn’t work I’ll just use one of the flashlight drivers I have on hand - I’m sure one of them will fit the bill, but I was saving them for modding some existing lights. Have to figure out how to reuse the voltage and current readings or I’ll have a gape to contend with….
OK so I had some time and it’s actually a comfortable 52 out tonight. Took this bad boy out; my numbers are getting worse and worse. Got 97,900 lux at 42.81ft, for 1,666,875 candela. Still pretty good, but a bit off the high of over 1.8Mcd from a month ago. Maybe I’m killing the LED? I do have another buck converter coming in so I’ll test it out. I still think it’s pretty good, but I’d like to try and get 2Mcd before I move on from this.