REDO: How much lux drop is normal? Again :)

From my meter, I loose 1 lux about every 6-8ish seconds immediately on a B158 and a fresh cell.

Is that a normal amount? I even soldered the MCPCB to the pill thinking that better heat transfer would help.

So my initial readings were off.

Initial lux is 40000. After 30 seconds, it’s 37900. That’s a 5.25% loss.

With those new numbers in mind, is that a normal amount of loss? Pulling about 5.7 amps at start.

(XP-L HI 3B on sinkpad, 22 gauge wire, a MTN-17DDm driver, bypassed springs.)

That’s only 1k lux in ~2hrs. You wouldn’t even notice that with your eye. And most likely the cell would be dead before then anyway :smiley:
The output will always drop off as you use a torch. As I believe, even with a boost driver ( correct me if I’m wrong )

I’d be very happy if my lights only dropped 1klux in 2hrs !

The output drop from heating up is normally (Cree specs) so that if your light gives 114 lux when the LED (T-junction) is at 25’C then it will give 100 lux when 85’C warm.
At 150’C there will be 82 lux left.
The battery voltage will also be sagging and add to the lux drop.

I also have a Brinyte B158, if you drive it hard it will get hot quickly as the B158 isn’t exactly suited to dissipating the heat efficiently.

You have the screw in pill and the threaded zoom battery tube, the thread’s aren’t good for heat transfer to the body which doesn’t have any cooling fins.

Thanks a lot everyone! I had never noticed the drop. I thought that maybe I hadn’t soldered the mcpcb to the pill correctly.

So my initial readings were off.

Initial lux is 40000. After 30 seconds, it’s 37900. That’s a 5.25% loss.

With those new numbers in mind, is that a normal amount of loss? Pulling about 5.7 amps at start

I do not know for a fact if that’s “normal” - but its almost pulling the max amperage for an XPL-HI.
So I would say ( based on my readings ) that indeed that’s normal with your set up. Also bear in mind the XPL-HI isn’t the most efficient x-lamp.