That’s good news, I almost got the Niwalker Vostro on sale but I’m glad that I got the K50 instead.
I wonder how the driver will handle solder bridged sense resistor pads.
Edit: Hoping that the head isn’t glued…
I think I'll turn mine into a K50M. (scan their product lists, you'll figure it out easy enough)
With an MT-G2?
I wonder what the max voltage of the driver output is.
If it’s higher than the K40/TN31 we’re used to, then the soldier bridging method won’t work and will likely fry XM-L2’s. Precisely calculated SMD resistors (1206 sized?) would be necessary.
If not, it’s going to be almost impossible to drive a MT-G2 with the stock driver.
What’s the typical max current the emitter sees in a standard K50 V2?
There are TK61's out there doing ~8A, at least tested in that realm - just fyi, probably the soon-to-be TK61vn V2.
Also, the 5 meter to 15 meter throw measurements will make a difference for some, maybe most lights, not all though. I measured a TN31 at 435 kcd or so at 5m, then rdrfronty measured the same light at 5m - about dead-on with me, then measured it at 15m and got ~580-585 kcd, so with that light, 15m does help. According to rdrfronty, once you get to 15m, further out distances don't make much of a difference, so he sort of standardized to measure his throw at 15m because of his numerous test trials at various distances.
Not sure what the stock amps is for a K50 V2, but must be up there to produce 1,600 OTF lumens. I'd be guessing at 4-4.5A.
Yes thought it must be close to the 5A mark which is I think is sensible and advantageous for emitter longevity and cell choice.
Modding not out of the question though 
I didn’t manage to get in on the group buy, they were gone by the time I saw it. But one of our members has asked me to mod his for him. So I’ll be posting my results here. I really won’t know what I’ll be doing to it until I get into it. Most likely just a de-dome, focus work, heavy wires, lap the star, best thermal grease and resistor mod. I would think that 6 or 7 amps should really be enough for this light. Keep it reasonable so it’s not going to kill it anytime soon. Anything more and you end up in that area where it’s really diminishing returns. I would think this will come really close to the TK61 and should beat my TK61 as it’s not running that high of amps. I’ll be able to post the results of the two up against each other. That should be an interesting match up.
I really wish I had gotten in on this group buy but that’s the way the cookie crumbles and at least I get to mod one.
I’m going to be following this thread closely. It’d be fun to see how high people push their K50s. Of course some emitters will fry at 8A, some might fry at 8.5 or even 9A. It definitely has better cooling fins than the TK61, but also has a slightly smaller reflector.
Sorry to hear that 18sixfifty. It was indeed a very nice deal and the lights did sell out quite fast. Seems like these are limited edition Supbeams indeed.
I can’t wait to get the light. Does anyone know the differences between the K50 and the K50 V2?
Subscribed! Thanks everyone.
So what would be the amp draw per battery for this light in standard form?
I’m assuming 1.5-2.0A per cell, so it’s quite manageable for any cell.
Things get a little different when modded, I’m guessing about 3.0-4.0A as the driver’s efficiency falls.
4.5A output is around 16-17 watts, and with 4 cells in series the current draw is tiny. It should be well under 2A even when the cells are dead empty.
I’m a bit new to modding drivers so I don’t really know much, but why does the driver efficiency fall as you mod it? I’m wouldn’t have thought adding a resistor or bridging connections would cause efficiency to fall so low.
Pushing 12-16A to the driver when the emitter itself will only be getting 7-8A?
With the cells in series, amps is amps. It's just at a higher voltage (more power in watts).
Max voltage is 16.8v, min voltage is 12v. High voltage low current input, to get a low voltage high current output. That's a buck driver.
Driver efficiency falls because more current through the driver means more heat, and heat is wasted electricity. The actual efficiency might not change much, but the amount of wasted electricity goes up.
That’s a good question. I’m not entirely sure, but as you push the inductor, diode, etc. beyond their rated specs, the efficiency of the driver seems to drop noticeably. When I started pushing 6.0-6.5A to my K40 and TN31, I noticed that the driver heats up pretty hot and sucks a lot of current from the cells. If the cells are almost depleted, the driver would try to suck more current for the lack of voltage. This caused my springs to heat up and lose their tension. Copper braiding them helped a lot.
Here’s a video of a voltage sweep with my modded K40. Note how the current draw shoots up to 6.69A when the voltage is about 7.5V.
Ok I see what you’re saying.
I wouldn’t have thought that the efficiency would drop to ~50%, but rather it stays relatively unchanged while heat increases from increased amount of electricity being wasted in the driver (proportionate to the increased drive levels) and of course from the LED.
The efficiency can drop, but not from 90-95% to 50%. I think something would catch fire if that happened.
I do think the efficiency does plummet to around 70-75% or below when modded.
The driver gets ridiculously hot, and the current draw from the cells seem excessive.
From the video, some quick calculations:
Emitter power: 6.0-6.5A x 4.0-4.2V = 24 - 27.3W
Input power: @0:33 3.65A x 10.0V = 36.5W
Efficiency: (24 to 27.3)/36.5W = 65.8 - 74.8%
Oh boy I know this too well… this is what fried my TK61 driver running only 5.75A. Getting a new 10A driver from Richard but only pushing it to 7.5A.
I understand that as voltage sag increases (or batteries deplete) the amps will go up to compensate [watts = volts * amps, and the power wants to go as high as possible limited only by driver or power input], but I still don’t understand why efficiency would drop that low.
EDIT:
I guess as supercooling decreases resistance in wires considerably I guess the opposite is very well possible. That makes a lot of sense now.
I remember from year 11 physics it has something to do with the atoms vibrating and flying in all directions causing collisions with each other within the wire, and by cooling them down they flow in a straight line. It would make sense that by increasing the heat energy within the wire it would create more atom collisions resulting in a higher resistance.