I’ve got hold of a few EV batteries “36V, 5,2Ah/187Wh”. 10s2p 18650s with a discharge capacity of some 500W, with decent safety margins (rated to 720W max, but they’re not exactly brand new and calculating from the capacity of the actual cells used, about 15A is the highest continuous, or even temporary, I would feel safe with).
My first project is a portable sound system with multi functionality for outdoor parties and “glamping” in general.
But seeing as the packs are 38cm long, 5cm diameter rods (~15”x2”), with matching aluminium tube, I just can’t resist building a “flashlight” based on one! Or a “lightzooka” perhaps! 
One very basic question though is, what kind of emitter array would one like to use for such a build?
9x 12V XHP70.2s in 3s3p, for a rated max current of about 260W should do the trick right? At least in theory… and they should still have the capacity for a “turbo mode” of almost double that IIRC.
Few emitters allows for more expensive ones with optimal light quality and efficiency, but what can be gained by altering the number/voltage/array in general, e.g. 6V in 6s, or simply more emitters in parallel?
Is it ultimately down to heat dispersion alone? I’ve seen tests where XHP70.2s handle as much as 50W, so nine of them is enough, in theory. (Or maybe twelve…)
The theoretical output of some 40000lm (@260W or pushed to the limit?) aught to be “enough”, and a “practical” output of quite a bit less should still get really decent runtime (and I could even bring a spare pack).
I don’t have experience building lights, so experienced input is very welcome!
Well met
Ted