If the outside of the flashlight was 78 C, the inside (the LEDs in particular, but also the regulator chips) would likely be quite a bit hotter, like 100+ at the LEDs. The 78 C measurement was after heat has already spread out and reduced quite a bit.
In the thermal image, even the body tube was like 65 or 70 C, which suggests that the battery inside was probably at least 70. And the battery’s rating isn’t a hard limit… it’s an arbitrary point along its curve for an average cell. Getting close to the rated limit is going to be unhealthy for it… just not as bad as exceeding the limit.
High-power turbo is hard on torches. It significantly reduces the life span of the LEDs, the battery, and often other components too. LEDs are typically rated at 50,000 hours of life at a particular power, temperature, and humidity… but the life span varies greatl depending on conditions. Like, a hot-rod turbo light may have LEDs burn out after just 50 hours, while a light driven at only a tiny fraction of its rated power could last for a million hours.
… and similar story for batteries. Fast-charging or fast-discharging it reduces the life span quite a bit, and heat makes this effect stronger. Also, fully charging or fully discharging it reduces the life span. It’ll stay healthier when kept closer to the middle, like 20% to 80% full.
Anyway, the unfortunate thermal regulation behavior doesn’t affect all Lume lights. It only affects the ones with loneoceans firmware with the “turbo temp extra” flag enabled. That’s the bit which makes it ignore overheat conditions until it is already well past the user’s configured temperature limit. It was added to make turbo stay at full power longer… but as a side effect, it also makes the light greatly overshoot its thermal target, and increases the risk of damage to the torch or its battery.
I haven’t merged that patch into my repository, and don’t plan to. My firmware releases aren’t affected.
To tell if your light is using loneoceans firmware, use the Version Check function (15+ clicks from off). A loneoceans build blinks out a model number, then a “buzz”, then blinks out a seemingly random series of numbers and "buzz"es. The version check format is:
- My builds: MMMM-YYYY-MM-DD (model number, then date)
- Loneoceans: MMMM-REVIDNO (model number, then git revision ID, hex number where A-F are shown as a “buzz”)
Or to be safe, on any high-powered light, take care of your batteries and try not to use turbo much. To help with this, Anduril can be configured to disable turbo. It’s usually fairly safe to set the ceiling to 130/150 or maybe 120 or even 100, and also disable turbo so a double-click goes only to the ceiling. On an affected light though, even just lowering it to 149/150 (with turbo disabled) would be enough to avoid the “turbo temp extra” behavior, because that only activates at full power.