I’m working on a big convoy runtime sheet and did some calcs for the sst20 2700k J4 bin that convoy supposedly uses, and 7135 chip selection. I have a 2700k 7135*8 and I regularly use the 10% level (~56 lumens) as a lantern with night adapted eyes and it’s an excellent brightness for reading and close activities.
The runtime @10% is also constant output for almost 9 hours before it drops below 95% brightness. LVP kicks in at 9 hours 57 minutes, 36 lumens brightness and 2.9v on the battery. For 30Q cell. Here’s the graph, just to give you an idea. 7135*6 or 4 should have much better curves for 100%/40%.
Hope this helps, my 2700k is my favorite light.