Teardown and Mod Thread of Courui XML2 Aka "Big Head 3x18650 Side-Switch Thrower"

I just popped my an E-Moli 26700 into my other HD2010 with the same East-92 driver but with the stock XM-L T6 and got 4.7A. A big improvement from the XM-L2 using the same cell.
I don’t really like tail readings much because the current levels jump around too much as compared to an emitter reading that is more stable using alligator clips rather than hand pressed leads.

Sure I understand that XML2 are about 20% more efficient at the same driver current, and that’s quite a lot more lumens…but is that really how it works out in the real world when the driver current drops a considerable amount due to battery sag. Diminishing returns on the XML at higher currents will probably rule the day, but I’m still curious.

I don’t really have enough experience with XM-L2s to know myself so I’m just curious if someone has directly put this theory to the test.
Say has someone done a direct lumens/output over runtime comparison on the same superbly copper heatsinked light like a HD2010 with the same battery to see which comes out on top. XM-L U3 vs XM-L2 U2 in direct drive showdown! :stuck_out_tongue:

In any case it probably doesn’t matter since XMLs won’t be available for much longer anyway.

The thing is though, you’d have to measure the actual lumen output difference not just the current. You may be driving the XML-T6 with more current but that old T6 is far less efficient at turning that current into Lumens than say an XM-L2 U2 and even 20% less effecient than the equivalent XM-L2 T6. This gap is probably far too big to jump with higher current alone. Closer bins and proper lumen measurements are where it potentially get’s more interesting…:slight_smile:

Boy. Am I ever getting confused.

I don’t blame you, splitting hairs is a confusing and complicated business :stuck_out_tongue: :bigsmile:

Yeah I know, cheating, it's not apples-to-apples unless it's on a XML board, but why go only halfway?

Another thing, semi-serious, stay away from copper MCPCBs if you want max amp draws. On aluminum the LED runs hotter and therefore pulls more current. Shouldn't it put out more light if the current is higher? No? :)

Thanks for the nice teardown Linus! This light will still be on my watchlist of lights very interested in.. (Im not pulling the trigger yet though)

Hopefully all info below will clarify some for those who have missed some of the info around XM-L vs XM-L2.

Having 3 cells to divide the current on, I would easily go with XM-L2. Which I even do in the majority of my single cell lights. It would be fairly easy to get 6A peak, or higher depending on cell. And you would also see 5A+ for a good/long amount of time depending on the cells... Having 2 or 3 cells in parallel helps limit sag a lot!

In general you either get higher output with XM-L2, or about similar output at lower current. But I had an example that was even worse (which I mentioned to Ouchy in another thread). So if you get an XM-L with lower than average Vf, and an XM-L2 with higher than average Vf, the XM-L could be brighter, in my extreme example with a partially drained battery it was 3,5A for the XM-L vs 2,2A to the XM-L2 with a drained battery. Its not common with such a large difference though..

As for lumen vs current:

(Direct copper mount, not copper MCPCB, but its probably quite similar)

6A to XM-L gives you around 1480 lumen.

In order to get similar output on XM-L2 you only need. 4,4A. Im not 100% sure what bins was used.

2,6A to XM-L2 gives you 1000lumen. 3A To XM-L gives you 1000 lumen..

And since the XML2's voltage is higher, which gives lower current, that also means the battery voltage stays higher for longer, which helps offset the difference in when the driver drops regulation and current starts to decline with cell voltage. I think it's pretty much a wash.

Boy. Am I ever having fun now.

Yep good sum up of your experiences thanks guys, it’s good to have a spread of information. What sparked my interest in this possible crossover performance situation was when I saw those XML U2-3C NW emitters on sale recently, was wondering if in a single cell light and highly driven it might actually result in a higher total output vs the newer equivalent available XM-L2 T6-3C emitters. Even if it’s only a slight difference or possibility I was curious if it was possible that the older tech could still outperform the newer stuff.
Also I feel safer knowing the current is being spread across 3 bond wires rather than just two but that may also be less relevant in reality.

I guess this is what it comes down to for me, knowing the output bin of an emitter can make all the difference when the differences are so small. Especially when you may have older emitters that are rated at a higher output bin and therefore gain an advantage over the newer stuff with a more efficient baseline.

I may just do this test myself out of curiosity with those particular emitter bins I mentioned above and see what happens. But as you say the variation between individual emitters even within a bin is probably going to make this stuff too muddy to draw any real conclusion from anyway.


Ok back to the big headed light! XM-L2s all the way with this one I agree! :slight_smile:
Speaking of which the tint of the one in my light is actually pretty nice, having used it a bit more I’d be pretty confident in saying it’s a 1C tint with a nice amount of green. Makes distant vegetation pop without being too obviously tinted. Surprisingly nice actually, particularly after fixing the focus. I guess the days of getting the horrendously blue XMLs in cheap lights are gone. :slight_smile:

I was a bit confused on the issue as well, but I think I understand a lot better now. Thanks for the explanation!

This flashlight looks amazing btw. :slight_smile:

It’s amazing and amazingly flawed all in one :stuck_out_tongue: I guess we kind of like them like the around here!
Wouldn’t be fun if there wasn’t anything to improve on though, would it… :wink:

The XM-L was T6. Match did the XM-L2 test when the emitter was new on the market. I believe it was T6 as well. Im just not 100% sure.. I assume its the same bin. But like you say, there are some difference within the same bins, and like I recently noticed in this thread (see the: "Why did I use a bunch of time modding this light for probably zero visible gain?" part). You can even risk getting a good difference in Vf on the same emitter. And on top of that, are you really 100% sure that the supplier are 100% trustworthy? There are many small factors can make results invalid..

But in this light, 3 cells in parallel will easily give you you 5-6A+. Even 3x protected NCR18650B should give you 5A+ on a typical XM-L2 based on what I have seen. And when you have an XM-L2 at those currents, XM-L just cant compete....

Are you planning on resistor modding the stock driver, or are you going directly to some DrJones stuff or a reprogrammed driver? Im curious what the stock driver are capable of. 0:)

I’ll be stripping the driver board eventually to go for a linear driver setup, so I’m happy to try and toast it and the emitter by doing some resistor mods first. :slight_smile:


So far I have not modded lights but I’m eager to try my hand at it. At the same time I don’t want to mess up any good ones so to speak. This light has really appealed to me and from the sounds of it has lots of potential. Given some of its challenges would this be considered a good canidate for a first time or should I stick with something more mainstream like a C8 or something?

Convoy C8 host would be a good first 'Flashlights For Dummies' project, lol. There are tricks to learn even for a build that uses all off-the-shelf parts, it will serve you well to start with something rather more difficult to screw up. :)

... just ordered one from KD; I'll put in a linear driver.

Thanks for the tear down Linus.

A C8 is a good modding choice for the first time, very little chance of messing anything up and parts are readily available and don’t have to be made to fit.
The OP reflector is also very forgiving in terms of getting a good focus and alignment, this can be one of the more frustrating parts of modding a throwy light. At least it can be for me and ruin the whole experience if it’s difficult! HD2010 I’m looking at you! :stuck_out_tongue:

With this light you may have fun doing basic mods… focusing the emitter, upgraded wiring, emitter swap, maybe a resistor mod etc, but to really get the most out of it and drive it hard it needs a bit more custom work. Adding 7135 drivers will also require some special fitting/heatsinking and considerations regarding the electronic switch.

Have a stab at a C8 first and see how you go, then look at this light once you know some of the basic pitfalls of modding :slight_smile:

Is it possible to change the switch into mechanical switch and use one of those common Nanjg 105C drivers?