There’s a chance I’ve messed up the calculations… There’s also the discussion of where you call the end to a runtime, for me, I like to look at length of time the lumens at a certain level are sustained for, ANSI runtimes are down to 10% of original output.
Zebralight generally recognised as having very efficient drivers- do be aware when comparing these lights to one another, the LED choice will have a big impact on brightness/runtime: cool white, low CRI LEDs are more efficient than wam white high CRI.
Small reductions in output would result in longer runtimes. E.g. that Reddit 519a graph shows 482 lumens at 1.5A. Running same calculation above, this is OTF lumens of 434Lm.
Driver at 90% efficiency uses 1650ma. 6200/1650= 3.75 or 3 hours and 45 min.
There’s a good review of the SC700d here showing the light does 945lm for just shy of 2 hours, which isnt too bad.
If you want good output efficiency you’d be better choosing a LED with greater efficacy than the Nichia 519a. If you’ve decided you’re definitely a lighting nerd, welcome, and you’ll enjoy the 519a, if you can tolerate the output/runtime trade off.
Edit to add: just to sense check my calculations:
XHP70.2 test (a generation old, but I couldn’t find .3 test) and at 4000K.
638lumens (about 575lm out the front) requires 2.71W (note conversion because the voltage is listed as a 6v emitter in that review).
Let’s use 90% driver efficiency again, the cell provides 3W. The 6.2ah, 3.7V cell has 22.9Wh capacity, so 7 hours…
Are 519a’s really that inefficient?!?!