I had the realization recently that the grow tents we use here in Canada for certain indoor plants are kind of a perfect integrating sphere-
No light can enter or escape, every surface is highly highly reflective mylar, the whole thing can be climate controlled, any temperature and wind speed you want, and it’s fireproof. It’s like it was made for this.
And I have an empty one so I started messing around with the ceilingbounce app and put together some very crude graphs of some convoy drivers. I haven’t calibrated lumens yet so it’s all just relative only meant to show regulation and runtime.
The reason the graphs don’t start at 100 is because the ceilingbounce app uses the output at the 30 second mark as 100.
All tests were at 100% mode with a fully charged Molicel p28a
3.12V ending voltage for both
3.41V ending voltage
Light was approaching 60°C so fan was turned on
2.7V ending voltage for both
That last one is a 5A linear driver with a swapped, not stacked, 10mohm sense resistor mod. In theory this is supposed to be ~10A but I get around 8A in this light at the most. Thought it could be a good comparison against the buck. Mostly they were thrown in as an afterthought. I might try doing one where they’re cooled enough to have no thermal stepdown at all.
All tests were done with the same 2 Molicel p28a 18650’s, charged in the same way to 4.205V and left to rest for an hour, settling to around 4.18V. I used an adapter for the m21b just to be consistent with the same battery. Cooling was done with a little 2W fan and ambient temperature maintained at 70°F. The c8+ buck has a bypassed tail spring.
I’ll get better graphs in the future just posting what I have now cuz…why not?
Added:
10°C ambient with fan
3.2V ending voltage