So I’ve been basically using my 2000K KR4 as my primary light in the house. On the desk while I work, having dinner in the evening, reading a book on the couch. Man do I love this thing…
Only thing is that (not surprisingly), the 18350s drain pretty quickly. Not a big deal because I have 4 that I cycle through. But today I got the 18650 tube back out and man, the light lasts forever with a Samsung 30Q. Like a couple hours and I was down to 4.05 Volts. I also was shocked at how much brighter the output is in max/turbo even thought I’m using high drain 18350s
If i’ve learned anything from The Fast and The Furious it’s that you can only shoot so much NOS into a Civic.
I dont have my copper FW3A anymore but I recall it didnt even last twice as long on Turbo. I think you do get a few more “shots” out of it until the light is totally saturated though. I think it also maintained like maybe 15-20% higher sustained brightness too. One quirk is copper lights sometimes “feel” hotter on the outside even if the electronics run slightly cooler. $.02 YMMV
My understanding is that by volume copper can hold approximately 60% more heat than aluminum. This means the copper takes longer to saturate with heat so in theory it might hold more before it overheats.
But on the other hand, copper also conducts heat far better than aluminum. This can be both good and bad when it comes to turbo modes.
It is good because the better heat conduction helps move heat away from the emitters and other electronics helping them to stay cool.
However, the temperature sensor that controls the thermal rampdown is located in the MCU on the driver board. A copper head may mean heat conducts from the shelf back to the driver board faster than an aluminum head. This could result in the light ramping down as fast or even faster than the aluminum version.
You can mostly override thermal rampdown with firmware settings. However, copper again shows a disadvantage. It conducts heat so well, instead of just the head of the light being too hot to touch, the body tube itself might become too hot to touch. The result is the limiting factor in turbo output changes from “protecting the electronics” to “protecting your hand”. It doesn’t necessarily help if the light is able to run on turbo without damaging the electronics, but you need an oven mitt to actually touch the light without burning yourself (and possibly risk the battery overheating and exploding).
Another thing: Copper conducts heat better and has more thermal capacity than aluminum. But you still need to get the heat out of the light. There are three mechanisms that makes this happen:
Emissivity - the hot metal emits the heat as infrared radiation. Shiny copper or aluminum has low emissivity (bad). Dark anodized aluminum and tarnished copper has high emissivity (good).
Convection - air circulating around the exposed pieces of metal takes away heat from the light.
Conduction - your hand absorbs some heat from the light.