Crash-testing a XM-L2 and a XP-G2 on copper Sinkpads

I just put an XP-G2 R5 2B on a 16mm Noctigon, with a huge aluminum heat sink and wired up to a Q-Lite 3.04A driver. With a single AW IMR18350 it will pull 2.99A. But stacking chips on the Q-Lite give it nada. No gains. Why is that? With 4 chips stacked and 4V reading on the AW , I got a Vf of 3.43V on the emitter. So why are the stacked chips doing nothing?

Maybe try a different battery. Voltage drop may be too much

I tried an 18650 Efest IMR, also an 18650 Samsung 20R. The chips didn’t allow extra amperage over the standard 3.04 board.

Therefore we can’t stack additional chips to the 3.04 Amp drivers? I’d better stay away from them then and use the old reliable 2.8 Amp Nanjgs.

Regular solder paste won't jump the gap between the anode and cathode planes on the substrate, even if applied across the gap it will separate when it melts. There's nothing in the gap it can stick to. The connection onto the die is the tricky part to deal with.

I did something similar lately: stacked 4 extra 7135's (380mA) onto a qlite (a very neat solder job I must say, the chips well heatsinked against the pill) and put it in a flashlight with a (dedomed) xp-g2, with a fresh cgr18650ch IMR battery. I expected about 4.5A, but I got only 3.6A tailcap reading (so without the switch resistance). So a bit more than the stock driver but not the full potential of the 12 chips. I did do all the possible resistance reductions, braided springs, thick wires etc. (I got 170klux throw out of the light, so I was happy anyway :-) )

Scroll up to post#55. You'll need a buck driver and 2 or more cells in series to go past what it will do in direct drive.

Ok, my driver wants to deliver 4.6A, to feed that to a XP-G2 it needs to deliver that at 3.8V (my own measurements). The driver itself eats 0.1V (or a little bit more?), so it needs at least 3.9V input. The cgr18650ch at 5A delivers that voltage only in the first minute (HKJ's measurements), so it does not stay in regulation very long . So yes, the desired 4.5A is a bit wishful thinking, but I could see that the first minute unless the switch eats away voltage as well (or in case of tailcap reading the DMM+leads). Pity, you are right comfy, I did not count on the higher voltage of the XP-G2, a XM-L2 needs 0.2V less for 4.5A current, so that should work a bit better.

I'm getting just over 4 amps on a Nanjg with 4 extra 350 7135's with a de-dedomed XP-G2 on copper. Also I've added 380 7135's stacked on QLite drivers - no problem. The Pana CH cell is good, but not as good as Samsung INR 20Q or 20R or SONY 30A rated cells. 4.5A may not be achievable though. Cells must be freshly charged - it ain't gonna last too long... I always pre-test my stacked drivers on a XML T6 mounted on a big heat sink to verify the amps it puts out -- much easier with XML's than XM-L2's because of the Vf issue.

Yeah using NCR-PD’s or Sammy 20R’s should help.

XP-G2 seems harder to push current through than XM-L2

Yes - and I swear de-doming an XP-G2 drives it up further - this has been noticed by RaceR86 too.

emitter magic!

It’s not an issue with stacking chips on a 3.04A driver, I have several that are doing just fine. It’s the requirements of the emitter itself that is causing the issue. It will take another type of driver running 2 cells to get the demands of the XP-G2 met with enough leeway to enjoy some run time.

Keep on keeping on!

Thanks Comfy, djozz, really appreciate the feedback.

You could build a test rig on an old heatsink with something otherwise useless, like a bunch of leftover XREs in parallel, that would be the right kind of load to let the driver run at max without frying anything. That would tell you if the driver is capable of doing what it should but not whether it will do that theoretical max on any one particular emitter.

For example two XMLs in parallel will run at ~5.7 amps direct drive off a cell that will only do about 4 amps direct drive into a single XML.

Thanks again for this testing and reporting djozz. Based on your work here, I decided to see if I could push a dedomed xml2 at 7 amps in a flashlight. Worked great for 2 or 3 weeks of off and on usage before the bond wires vaporized. I believe this is consistent with your reporting here as there are a lot of potential variables and differences that could account for my emitter blowing at a lower current.

I said the bond wires vaporized. I don't know if they actually vaporized, but I can't find them. They were resting on a blob of silicone and now they are gone. There was a flash before the emitter died. The dedome was done with gasoline. I know gasoline can weaken some metals. I learned that from a motorcycle drive chain.

I don't have precise measuring equipment like you, but I think current to the emitter was probably not much over 7 amps. I used short 18ga wires directly connected to my DMM and soldered directly to the driver and emitter base. I have about 7 DMM's and the one I measures consistent with the others. The driver gave rock solid current readings every time I tested it through out the build process, both with 2 and 3 cells.

The emitter still produces some light. Low is like firefly mode and high (7 amps) is dimmer than a typical moonlight mode. I'm guessing that there is enough metal particles on the silicone blob to deliver some current. The third wire that is off to the side and appears to have a diode or something appears to still be intact. Any thoughts on this anyone?

That's interesting... Then those claimed 6.5A TN31's may not last too long out there, but it's a different setup for sure. The side wire is not needed - it's for EMG or something - can be removed with no harm done -- been posts about that.

Actually it does “X (named ex /ˈɛks/, plural exes[1])”

Hopefully not Tom E. You guys are real good by the way. I can't get my TN31 to reach 6 amps. I think the TN31's have better heat sinking than my DST has. They have that really nice large copper base. That has to do a better job sucking out the heat then my set up.

EDIT: By "Hopefully not", I was trying to say hopefully the TN31 owners out there running at 6.5 amps don't have problems with short emitter life. Sorry for the confusion. I am usually in a rush when making posts as I have very limited time to make them most of the time.

whothewhatnow? o_O

Correlation is not causation. 'X happened at the same time as Y, therefore, X must have caused Y!' Much more plausible explanation is that it was an o-ring chain and the gasoline affected the o-rings and/or grease inside, and the lack of grease killed the chain. In 20+ years of living and breathing cars I have never heard of gasoline doing anything like that to any kind of metal.

Thanks comfy, I choked on my coffee as well when I read that.

Cleaned motorcycle chains in gas for years. Stretching was my only issue with chains. Loved my shaft drive! :slight_smile:

THIS JUST IN: GASOLINE HAS BEEN DISCOVERED TO EAT THROUGH GAS TANKS, CREE EMITTERS ARE SAFE TO DE-DOME THANKS TO KRYPTONITE DIE CONSTRUCTION.

More on News at 11 on your favorite modding channel MTG2 Live Now! :stuck_out_tongue: