Lucifers don’t do “turbo” modes (which is partly why I like them). All the modes are sustainable for the intended usage, which is moving sports (orienteering, skiing, running, dog sledding, etc.) that inherently have a cooling from movement, with the higher modes intended for higher speeds. If you are talking about usage without movement, such as a work light, Lucifers will hold the mid mode and maybe high depending on the ambient temperature. They hold the lumens flat. If it gets hot enough or if the battery is depleted enough that the lumens can’t be held flat, the light kicks down to the next lower level (all of this runtime behavior is exactly what I bought the light for as a sport headlamp). There is no slope in the runtime graphs, just flat lines and step downs when necessary.
I have had the L+ for a year. To give an example, in boost mode (3500 lumens), I’ve found that the amount of cooling needed for that to be stable is, for one combination of speed and ambient temperature, about 17 minutes per mile (a moderate walking speed) in 20s degrees Fahrenheit. Slow down to 20 minutes per mile in the same mode and ambient temperature that’s the borderline where it wants to kick down from “boost” to “high” (1800 lumens). In real life when not playing around with a new headlamp, I don’t use 3500 lumens at a walking pace.
I bought it for its capability at the “high” (1800 lumen) level and picked the battery pack to cover my typical 2- to 3-hour workouts (cross country skiing in winter mostly). Theoretically, it should be good for about 3 hours to where the battery is depleted enough to have to drop down to “mid” (850 lumens) with the 2x21700 battery pack that I use. I have used it on night skis up to 2:40 long without dropping from the 1800-lumen level and haven’t tried to go longer. 850 lumens is great for skiing most of the time, but higher is nice when the woods are darker out and reflect less light back, such as when things are wet. The levels pass my sniff test of being at the same level at the end of my skis as at the beginning, pointing it at my house and seeing which trees are lit up behind the house.
I have a screenshot of a runtime graph from a YouTube review of the older “L” 3200-lumen model from when it was posted on Lucifer’s website (but later removed) presumably tested by Petr of Lucifer on his older integrating sphere (he just bought a much fancier, presumably more accurate one). It didn’t quite match up with his runtime tables (a bit higher in lumens, a bit lower in runtime to 70% of initial lumens, assuming battery was fully charged) but unless you believe it was entirely faked, it at least shows the runtimes are all flat with none of that turbo drop in the first 1-5 minutes that I hate for sport usage in almost all BLF-favored lights. I doubt it was faked based on the half dozen times the output dipped down and back up immediately as well as what I’ve seen with the Lucifer headlamp I have. Maybe he pulled this graph from the website because he wasn’t happy enough with his old integrating sphere.
I’m curious about what Lucifer will post from his new integrating sphere. His teaser was testing the L+ at 30 seconds getting 3,8xx lumens.
By the way on the L+ at least, the cooling fins have quite a large surface area:
Additional notes: I wear the headlamp under an “active insulation” hooded jacket when skiing in cold temperatures, so the battery pack stays warm against the back of my head even when it’s -15 F, while the lighthead is exposed to the wind/cooling from my movement on skis or running, so a remote battery pack headlamp is much more useful for winter usage (a point for Lucifer S2X+ over the Zebralight for winter use). An L-shape 18650 headlamp typically needs to be run pretty high for the battery to stay warm from the internal resistance to not to lose performance because it’s exposed to the cold. If you start a ski before it gets dark with the headlamp off and then try to turn the headlamp on an hour later when it gets dark, there’s a good chance the battery will be dead. An L-type headlamp needs to kept warm kept next to your skin (hand pockets on my jackets are not warm enough) or turned around backwards on your head and kept under an insulated hood until you need to turn it on, which can be annoying.
