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

Just want to say at the start, this isn’t a full review of this light. Just an initial impressions and technical teardown, to see what this light is all about.
It’s also done firmly with the idea of modding in mind, and frankly if you’re looking for a light that works great out of the box without having to get your hands dirty. I can say right now, this light probably isn’t for you :slight_smile:


Right, so this is a relatively new light and was brought to our attention by Pok a few weeks ago in this thread

It has some very interesting features and a form factor that I (and quite a few others) found very appealing.

Key interest points that caught my attention were:

1. Big head and reflector. 75mm head diameter. Combined with and XML2 this should offer some very good throw performance. Also a decent sized reflector for bigger emitters like the MT-G2 perhaps.
2. Electronic side switch. Rare to see this type of UI on a thrower.
3. 3x 18650 in Parallel as a power source. This offers very flexible driver options for modding along with great runtimes and high current potential even with weaker cells.
4. The colour :stuck_out_tongue: Non-black flashlights always catch my eye :slight_smile:

Ok so does it live up to the expectations, let’s find out…

First up some shots from the outside. This is a very nice looking torch with a well balanced and chunky feel. I love the aesthetics and finish on mine. Really nothing to complain about at all.

The reflector is indeed aluminium, and what a reflector it is…more detail below.

In terms of overall size it fits in almost perfectly between a HD2010 and a BTU Shocker. It’s not a small torch by any means but it sits in the hand really well and the side switch makes operating it a total breeze.

The side switch falls perfectly under your thumb/index finger and is easy to find even in the dark.

The machining is very good overall, no sharp edges or burrs anywhere and the anodizing is really attractive and even with a dark/gunmetal grey colour. Fit and finish is all really good.
The electronic side switch is probably very similar if not identical to the type you’d find on a SkyRay King or similar, a small SMD switch with a machined aluminum plunger and holder sitting on top. Very slightly rattly if you tap the switch lightly with your finger, but I’m sure that could be easily fixed with some double sided sticky tape.

The diamond knurling on the handle isn’t particularly deep but the large recessed parts of the the handle offer a pretty good grip. Should be fine even in wet conditions.
There’s single o-rings in all the usual places and as long as the side switch cover is decently watertight I’d imagine the whole thing will handle a bit of water just fine. Again I’m not going to go into detailed testing on stuff like this. At least not at this stage.

Threads are not square but they are smooth and the front ones even came greased so no problems there. The “tailcap” screws off and there the threads are anodized and completely dry. But again they feel like good quality cut threads. All orings were dry and the bezel oring is fairly loose and can get jammed when reassembling the light so watch out.

TailCap Threads

Battery Tube Threads

Finally here it is next to another “grey” anodized light. The colour on the Apex/Solarstorm is considerably brighter so that should give you some idea of the colour of this light. I like them both and would take this dark gunmetal grey over completely black any day!


Ok so that about covers the exterior. Lets tear this thing apart and see what’s inside!

First lets take a look at the battery carried and driver contact plate.
The cells are inserted in parallel and there is no clicky at the tailcap end so all it needs is a set of springs and a contact board to transfer ground from the batteries to the flashlight body. Let’s take a look how that’s done here.

Here’s the contact board for the driver and the + contact ring in the middle. This is all the same setup as a SkyRay king/Apex 5t6 except with 3 cells instead of 4.

Inside the battery tube is a 3 cell carrier machined out of the solid tube, it’s quite a substantial and weighty piece as a result and helps balance the big head nicely. The contact springs are a bit flimsy and could do with being replacing or at least adding some copper braid.

On the other side we see the contact plate that the springs mount to and in place of the usual reverse clicky switch we have a filament from a tungsten bulb…or maybe it’s a low amp fuse designed to protect the led. Or maybe a built in heating filament to keep your hands warm during the winter. Not sure, but whatever it is it will do a great job of turning current into heat that’s for sure! :wink:

Honestly what were they thinking, this is a ridiculously thin wire (probably 26AWG) to handle even the modest 3A that an XML can draw if driven to spec…not to mention what this light should be driving the LED at!
This just has to be replaced and it’s the first sign that if you don’t own a soldering iron then this light isn’t really for you.

Tail parts laid out.

Next up we take a look at the front of the light. First things first, lets take off the bezel and check out the reflector.
There was some concern and lack of solid specs about this reflector, many of us thought it might be a plastic unit going by the pictures posted on the Wholesale website.
Well I can confirm now that this reflector is indeed Aluminium and it’s also probably the nicest cleanest and smoothest reflector I’ve ever seen come out of a budget flashlight. Not to mention one of the biggest single XML reflectors I’ve seen! This thing is fantastic! :slight_smile:

Definitely Aluminium

The surface under the coating is free from any machining swirls or edge burrs or any of the other machining artifacts that give away the fact that it’s an aluminium reflector.
There is also no haze or dirt visible on the coating even when the light is turned on and generally it puts the average HD2010 reflector to absolute shame!
Lastly but also nice was the lack of any dust inside, in fact I didn’t want to mess it up at all by taking photos of it without the glass lens protecting it so you’ll have to take my word for it. :stuck_out_tongue:

Or you can use this closeup photo from the outside, although it doesn’t really do it justice :frowning:

The lens on the other hand, while definitely made of uncoated glass was pretty dirty and could do with a good clean with an optical cloth. I fact to better show off the impressive reflector an AR coated lens is a must mod for this light. Just hope we can find one in the right size.

The dimensions of the reflector are 70.5mm x 47mm and the hole for the led centering ring is 8.5mm
So other centering rings should work.

The glass lens measures 72mm x 2mm thick.

Now despite how nice the reflector looks in this light, the beam and hotspot profile it produces is probably the most disappointing thing about this light. It’s anything but well defined and shows the typical double intensity ring with a brighter center of a badly focused emitter.
The emitter itself is perfectly centered thanks to the centering ring but looking closely you can see that the emitter doesn’t sit very deep inside the reflector.
Removing the reflector confirms this, the plastic centering ring is very tall and only the very tip of the XML2 dome is actually sitting above the flat part of the reflector. Really not good, most of the light it produces will be hitting the centering ring and not the reflector in this setup.

The next thing I noticed with the reflector gone is that there is in fact a pill inside this light, the shelf that the emitter sits on is a removable pill that threads into the head.
Again slightly disappointing because I was hoping the shelf was machined out of the body of the light itself. However this isn’t the end of the world, it may be relatively thin but at least it’s solid underneath the emitter pcb :stuck_out_tongue:
Prime opportunity for machinists to make a copper shelf replacement… Ryan, VestureofBlood? Who’s up for it!? :wink:

Pill unscrewed and again showing the measly 26AWG emitter wiring used throughout this light. It’s really only appropriate in connecting the smd switch to the board but they use it for everything here…and generous lengths of it to boot! Horrible but relatively easy to fix.

At least there’s no hole under the emitter!

The “Pill”/shelf is a little over 2.5mm thick and here you can see just how high that centering ring is in relation to the XML dome. Not enough of the emission angle of the led is actually visible to the reflector. Again this needs to be fixed with a shorter centering ring and better wiring, hopefully the spacing to the relfector will still work and the shelf can screw out far enough to get a tight fit. We’ll have to see what can be done but I definitely intend to try these mods soon to see what this light can really do!

The emitter pcb itself is aluminium and glued to the shelf using a grey type of thermal adhesive/fujik. Pretty standard stuff and not really too bad, definite room for improvement though.

I’m also keen to see if the Courui branded version of this light available from kaidomain suffers from the same problems or if they have improved it.

Next up we tackle the driver.

The switch UI is a pretty standard electronic switch affair. Press the button once and the light comes on in High, then press it again to switch to low. One more click and the light turns off. The “low” mode is not particularly low however, maybe 50% which isn’t really low enough and it has very visible PWM.

A long press on the switch ~2secs activates a hidden strobe. Which I quite like since it’s only there when you really want/need it…ie very very very rarely! :stuck_out_tongue: Otherwise it’ll never bother you.
I don’t own any Skyray King type lights but from what I hear the UI is probably very similar to one of those.

Not terrible and switching modes with the side switch works great but a driver swap is what I’m going to be doing with this light. Maybe try a DrJones momentary switch driver or have a go at flashing my own. We’ll see.

I don’t have any idea yet what the driver delivers to the emitter and frankly with those crappy wires in stock form it can’t be very impressive. On top of that with the stock centering ring a lot of the light is missing the reflector so that won’t help it’s output figures much. Still I’ll reassemble the light in stock form and take some tailcap measurements when I get a chance.

The momentary switch is easily accessible by unscrewing the retaining ring as such.

Below is a SMD momentary switch glued into the housing.

The driver pops out from a firm push from the inside and this is the wiring…all very thin and the emitter wires are also fairly long. Not a good combination for high output…
The driver board has a diameter of 38.5mm and is press fit into the body.

And for the driver gurus, here’s a closeup of the driver. I’m particularly interested in the 16 legged MCU, haven’t seen one like that on a flashlight board before :slight_smile:

Ok so that about sums up my first impressions and teardown.
In summary…

The exterior and build quality of the light in general is really great, better than expected especially for the price. Unfortunately as a tradeoff the electronics and general assembly of the working components of the light leaves a lot to be desired and I really wouldn’t recommend the light if you intend to use it in it’s stock form.
And I have yet to see just how much can be gotten out of it when fully modded, but I’m optimistic that this can be turned into a fantastic light.

Get it if you want a fantastic modding host in this form factor, can’t wait to get stuck in to this myself….although I’m sure there was something else flashlight related that I should be finishing first…:stuck_out_tongue:

…and get it fast before they replace the reflector with styrofoam and downgrade the wires to 30AWG!! :bigsmile:


Thank you for the tear down. Now I don't have to buy one.

Great looking light for the money and it would probably be good for an XM-L2 or XP-G2. Unfortunately, that huge flat on the bottom of the reflector won't be too good for an MT-G2, which needs the reflector sunk down to over it, to get a tight spot. Of course, it is big enough around that one could bore it to where it would fit down over a 20mm Copper star with the MT-G2 on it and probably get a good spot... Or, open it up so a Wavien collar would go in over the MT-G2.

Maybe it won't be such a bad idea after all. Someone needs to do a Wavien collar with an MT-G2 here... Guys... Guys, you listening? Not me, I got too much to do, so one of y'all needs to step up and do it!

Again, great tear down and good photos.

Their profit, using 26 rather 20 awg wire, is around 0.05$ per flashlight.

Thanks for the teardown! Great write up! Shame on that "pill/shelf"


Thanks for the tear down. I really like it. Awg 26 will drop <100mV so, I wouldn’t call this super bad…
Is there nowhere a name printed on?
Any current or lumen measurements? Throw compared to hd2010?
I guess tailcap can be locked out?

After you measured the current what about, modifying the sensing resisto…?

This light would probably be a nice one for Groupbuy…

awesome review… hmm kind of slight regret didn’t get this light… particularly since I already owned big head flashlight such as TN31 and crelant MT-G2 lights

I'd love to hear about emitter current after you upgrade those bulb filaments 26ga wires.

Oh, and is it in fact an XM-L2? Hard to tell in your closeup pic.


Mine is completely unbranded since I bought it from Shenzhen Wholesale. Shenzhen Wholesale
The light is now also available from Kaidomain under the brand name Courui 1600 xml2 or something vague like that. Kaidomain link
We haven’t had reports yet of this version but I suspect it’s the exact same light just with a name on it.

Also I’ve seen some pop up on ebay recently with the same brand on them, also available from willbuying.com. Check the original thread linked above to get some more details about buying one.

I can’t measure lumen output or even lux at the moment so I wouldn’t be able to give you any specifics yet. But I can tell you that in it’s completely stock form the light certainly doesn’t out throw my modded HD2010 running 5.5A. And I wouldn’t expect it to, (even when running at the same current) until that led centering ring has been shortened or replaced and the led is better focused. As I said there’s lots to improve on this light before it’s performing at it’s potential.

I will measure some tailcap currents when I have the light reassembled though and post them here.

The tailcap doesn’t really do anything except cover the back end of the light. It’s not part of the electrical pathway at all. The front threads are not anodized so locking out is probably not possible by simply unscrewing the battery tube a turn or two.

Also forgot to mention that the contact between the battery tube and the ground contact ring of the driver could be improved. I had some flickering and wavering of power when testing, think that’s because the contact board isn’t in direct pressure contact with the edges of the battery tube. Instead the board is simply press fit into the head of the light and makes contact ground contact on ly through those solder blobs you can see on the top side of the driver board ground ring. It’s really not ideal either, again I’d hate for someone to buy this light and expect it to great out of the box, based on the light I have here it probably won’t and will need some considerable tweaking and modding to get it to a good state.
Be warned, you’re in for a project with this one…but if you’re up for it it should be a fun project with a great final result.

Yes the light is definitely equipped with an XM-L2, sorry my photos were a bit rushed. No idea what output bin it is though, no way to tell and it wasn’t advertised as being a specific output bin emitter so I would think XM-L2 T6 probably. Tint is hard to say too since a fair bit of the warmer light from the edges of the emitter is being swallowed up by the centering ring but it looks fairly close to my XML U2-1C emitter. Would guess it’s either 1B or 1C.

Thanks for the clarification.
Of course lockout isn’t possible, I am a bit tired or whatever…

Yeah could give that a go, don’t know much about it though. I’d need some suggestions from the driver gurus to find the sense resistor and figure out the conversion values and whatnot. I’ve got some smd resistors of various values laying around that I could use.

Here’s a bigger shot of the driver board.

There’s actually not all that much on the board.
Any idea which the sense resistor is? I know there’s only two on there but I haven’t done this before :stuck_out_tongue:

The R200 resistor is the sensing/limiting resistor. So after you have measured the stock current we will see further.
Do you have a experimental power supply? You should test if it is regulated at all.

I am a bit unsure because the r200 Is just in the input path of the little transistor and I can’t see a trace from the source side going to the controller…
But it could be a sensing resistor as through the source of the small FET flows all the current, you should check if there is a trace from this point to anywhere to actually measure something…
Interesting that there is so much empty space left on this driver board, maybe this is just a cheapo variant of a more complex driver. Looks like if there could be another identical circuit on the empty space…

Ok cool thanks :slight_smile:

There's lots of promise if someone does a redesigned copper pill for this. Thanks for the teardown.

Thanks Linus - subscribed.

Hopefully my KD one will show up soon.

Yeah absolutely, plenty of space inside the driver cavity for some extra heatsinking mass and the threads in the head are considerably longer than the thickness of the shelf. Currently those threads make very poor contact to the emitter shelf.
I would definitely be interested in a copper pill for this light!

Ok I reassembled the light and I’m reading 2.58A across the tailcap “filament” attachment points on high.
Fully charged senybor 18650s reading around 4.16v after the test and it stayed stable at that reading for a good few minutes.

I didn’t take note of the reading on low because my meter doesn’t like the low frequency PWM current signal. It gives inaccurate averaging results.

I have 1 loose r200 (0.2 Ohm?) resistor of the same size as the one on the board and a roll of r500 and r100s but they are smaller, like half the size.
If I added the extra r200 in parallel to the sense resistor should I be seeing around 5.2A at the tailcap?


Subscribed :slight_smile:

-Jamie M.

Ok another small update, just replaced the original tall centering ring with a nice flat one and as expected this has made the world of difference to the hotspot and beam profile.

The centering ring I used is one of those white plastic ones with the wings on both sides and not much more than a slightly raised section around the emitter square. It won’t work if the emitter is not already pretty much in the center and can take a bit of coaxing to lock the reflector down right in the center, but this is the type I’ve had the best luck with centering HD2010 reflectors and it’s worked superbly again here.

The emitter is now sitting almost completely flush with the flat shelf of the reflector and it’s now pretty much perfectly focused. The spot is really nice, even and tight with fairly sharp defined edges. I’m sure that’s the perfectly smooth finish of this reflector that’s providing the definition.
It’s much more defined in fact than a nicely focused HD2010 and the spot is about 20% smaller.
So yes this light will out throw a HD2010 if given the right treatment :slight_smile:

Here is a direct side by side comparison between my best HD2010 running at over 5A on copper and the Big Head running at the measured tailcap current of 2.6A. I think I need to measure emitter current because this thing is keeping up with and maybe already surpassing the HD2010 in perceived lux! :stuck_out_tongue:

Distance to wall is 2.5m, Bighead on left and HD2010 on right.

Such a shame it didn’t come like this, would be so much easier to recommend if the beam profile was nice right out of the box…

Wow, talk about flawless beam!!

Subscribed for outdoor beamshots :slight_smile:

-Jamie M.

Thanks for the tear down. Great pics and summary of the light. Now I don’t have to do it myself - just the build log. :slight_smile:

I am slightly disappointed with the visible PWM, as I would like to use the existing driver. It is good to know that there is enough space in there to use my own driver though down the track.

Regarding the resistor mod, from the LD-29 thread , if you were to simply replace the R200 resistor with an R100 resistor, you should see an immediate double in current going into the LED. I plan to do this for the XM-L2 version light I will build. For the XP-G2 version, I plan to stack three R120 resistors and put them on top of the existing R200 to get around 4A from the tail cap. Both lights I am building will be de-domed.

Note that, the above figures are using your own numbers. To reduce resistance throughout the light, I intend to use higher gauge wire in place of the existing wires, along with copper braid the springs, as you have suggested.

edit: I am hoping that this light can dissipate the heat coming from XP-G2/XM-L2 being driven at >4A.

edit 2: just looked at your pics of the pill again. Man, is there a lot of space in there. Thinking out loud, me thinks soldering copper on the bottom of the pill should help with increasing the heatsinking mass, therefore, help with dissipating heat.