Well done New_Moon.
The hotspot looks beautiful.
Yeah, the 5200 is a pretty old design. It’s got quite a bit of voltage sag compared to newer cells.
I would not trust a DMM amp reading. I’ve seen a wide variety of inaccurate results. It’s better to use a clamp style ammeter. Still, this is not a high amperage range, if your using a Fluke or some high end meter it might really be 4.4A. Maybe there is some efficiency loss in the driver at high levels.
Jason, I think he’s saying the driver is set up with 7135 regulation chips to have 4.2A (11 chips for 4.18A), but it’s actually making 4.4A at the tail. There would not be an efficiency loss in this scenario, but a gain somewhere. Which of course, is highly unlikely. Puzzling, if you have chips stacked to get an added up current you do usually see a loss, even if slight, it’s just not going to make more than the chips are rated at. So something is off somewhere. Probably in the meter.
Nice light though, really diggin that hot spot! 
My multimeter isn’t anything special, it is a budget model from Ideal. Checking it again tonight with the battery now about 70% charged I am getting values now between 2.9 and 3.6 so the 4.4 I got earlier isn’t reproducible and probably was in error. Maybe I will recharge the battery and use some 16 ga wire rather than the test leads and see if I can at least get a consistent reading.
Dale you are correct about the set up with the 11 regulation chips, sorry if this wasn’t clear in the original post. Rain has stopped and I’ll see if I can get some beam shots outside tonight alongside my stock D1S, with my digital camera I should be able to dial down the exposure enough to get an accurate representation of the hot spot compared to what I could get with my phone camera.
Jason, “Yeah, the 5200 is a pretty old design. It’s got quite a bit of voltage sag compared to newer cells.”
An apt description of most of us… 
Compared to SOME newer cells this is true, but not all… this is still a viable cell by any measure. We tend to get caught up in the New and Improved and forget how well the Tried and True can serve us.
My Canon 1Ds MkII is a dinosaur, still using proprietary NiCd battery pack (I do have a new aftermarket NiMH pack though) Yes, a substantial portion of it’s 3 lb body only weight is the 10 AA cells it carries. It is a 16.7MP full frame sensor that rivaled Medium Format camera’s in quality when it was introduced at $8000 for the body only, almost 15 years ago (Sept, 2004). No video. No live view. Bells and whistles it does not have. But it takes awesome pictures and is built like a tank! This was the go to camera for pro photographers in it’s day! I still use it today, albeit for a lesser segment of my work as the 5D Mk IV is astonishing in it’s own right.
I was just making a comment about the Keeppower 5200. It’s fine for that low current driver. Not so great in a FET driver.
No biggie.
But it IS also good for an FET driver, when you want longer run times this cell will work beautifully. Perhaps not as much initial output but sustained output will be greater, so it all depends on the use cycle at hand.
I made an L2 with 2mm² White Flat and an L4P LD4A driver set to 7A (the sweet spot for this LED).
330kCd after some minor reflector height tweaking 
And here I was , thinking 5.5A was the White Flat sweet spot,
I just did a similar build yesterday but with an L6 and Mtn Electronics Max Buck driver at 5.5A. Initially I saw a 335Kcd reading but after some tweaking to make the beam more pleasing to my eye it shows 265Kcd. Might have to look harder at the reflector positioning.
I cut the emitter shelf to accept a 32mm Maxtoch XP MCPCB, also made a nice beefy copper adapter to allow the use of the 20mm driver, soldered in solidly the driver shouldn’t run hot at all. The stock brass retaining ring holds the adapter in.
If I remember correctly it makes 821 lumens…
That’s a 2mm² WF though, the little ones are not that tough and peak at about 4,5A
Ah, I have the tiny ones I think… guess I never made the connection there are two sizes.
yes best drive currents are 4A for 1mm² and 7A for 2mm²
I have fitting buck drivers for both
I finally got out the old Canon S2 IS so I could share some outdoor shots of my 7135 x 11 Osram 1 mm flat white L2 build. The L2 is on the right compared to a stock D1S 400k XPL HI on the left. Distance is about 10 yards pointed at my garage door.
!https://imgur.com/ewDnQ46!
This is the same shot with the shutter speed turned down to 1/2000 to give another perspective of their comparative beam profiles.
!https://imgur.com/Ht5rjnc!
I also got a couple shots of the beams going upward where you can see the Osram is significantly tighter. The cooler tint exaggerates the difference in brightness but the hot spot is a fair bit more dense than the Emisar. From the side:
!https://imgur.com/3LiquDF!
At an angle looking up as the beams converge:
!https://imgur.com/52OKvcY!
This one is with the camera between the two lights looking upward.
!https://imgur.com/vgW1ZdD!
Here is the L2 alone:
!https://imgur.com/quaMcwk!
Thanks for looking. Also I had some trouble with formatting so images are linked rather than embedded.
From New_Moon:
I finally got out the old Canon S2 IS so I could share some outdoor shots of my 7135 x 11 Osram 1 mm flat white L2 build. The L2 is on the right compared to a stock D1S 400k XPL HI on the left. Distance is about 10 yards pointed at my garage door.
This is the same shot with the shutter speed turned down to 1/2000 to give another perspective of their comparative beam profiles.
I also got a couple shots of the beams going upward where you can see the Osram is significantly tighter. The cooler tint exaggerates the difference in brightness but the hot spot is a fair bit more dense than the Emisar. From the side:
At an angle looking up as the beams converge:
This one is with the camera between the two lights looking upward.
Here is the L2 alone:
Thanks for looking. Also I had some trouble with formatting so images are linked rather than embedded.
L6 mod Im not sure this was the best thing to do. I keep stuffing the the threads on screws so thought soldering the mcpcb to a threaded copper slug that screws into the light was the way to go. The metal that is cut out is replaced with copper and the actual surface area of the led in contact with the aluminium heat sink is increased.
3 cells doesnt appear to worry the stock L6 driver
grin do you mean we can use 3s battery with stock driver?
I ran one for about 45min couple times and seems ok
I have an issue with my L6 after doing a spring bypass on the switch spring. It has the MTN FET driver, XHP70.2, two Orbtronic 5750mah 26650s that can handle 20A, and I used some 18GA wire for the bypass. I was testing the light outside at full power and it suddenly went dim to maybe 20% brightness and I can’t get higher than that now. The battery check function still works and I can ramp the brightness from almost nothing to this so I don’t know if I burnt out the driver or the LED. The LED still works but I did notice that it was only lighting up 1/4 dies instead of 2/4 at the “moonlight” level shortly before this happened. It doesn’t look like it’s damaged but I am not really sure. Anyone know what it could be?