Why not four 21700? That would make the flashlight bigger and deliver more current to sustain the 20000 lumens longer. Also, it would allow a 6V configuration and using flat top cells.
Any idea what leds they will be using and if there will be a high CRI option?
My guess is SFT40, XHP50.3 HI or maybe even one of those new chinese LEDs. I’m pretty sure 3 21700s can push a lot more than 20k lumens.
Will it work with flat tops cause high drain button top 21700s are pretty much impossible to find in the UK and can’t be shipped either unless inside the light.