Courui Big Head overhaul with XP-G2

I know there's already a few threads going for the Courui, but I thought I'd put this up as a quick reference that addresses the issues with the stock light.

The only components I have replaced are the stock wiring, as it's about as thick as a gnat's hair, & swapped out the MCPCB for an XP-G2 on a 32mm Noctigon. I also added a tail switch for lockout.

I started at the rear of the light by using 22 gauge silicone wire to upgrade the springs;

Then on the back of the board, removed the tiny stock wire & added an Omten switch, connected to each via by 18 gauge wire. A 13.5mm hole was also drilled in the cap to accommodate the boot;

Next was the pill assembly. The pill was turned over, sanded flat, drilled & tapped for the 32mm Noctigon, which was also lapped. Screw holes were countersunk to avoid interference with the reflector base.

I didn't bother with sanding the pill all the way down to remove the grind marks, as it's really not necessary - the copper board is doing the work here, & there's plenty of surface area where it mates to the pill top.

The underside of the reflector is completely flat, & 26mm wide, which is going to make things tricky to get it sitting low;

I figured the best way would be to make up some thin copper tabs, & get the wires away from the reflector. I also filed a small bevel on the base of the reflector for added clearance.

Here's the pill assembly ready to go, with the now de-domed XP-G2. I used an XM to XP centering ring, which was sanded down until it was flush with the LED base, then attached with a small wipe of super glue to prevent it from falling into the reflector.

The driver was then modified by replacing the R200 resistor with a direct bridge, & replacing the stock LED wires with 22 gauge. No need to replace the switch wiring.

I bench tested the driver at this stage, & measured just over 4 amps to the LED, using a single cell (25r) & long jumper cables & alligator clips. Installed in the light, the actual figure will be higher without the added resistance of the test leads.

I also added some solder blobs to the battery side of the driver negative ring, so as the battery tube presses up against it when installed;

Pill tightened down in the body & wired up;

Light is assembled & checked for operation. As some other members have noted, with the resistor bridged, there is always a small amount of power getting to the LED;

A bonus Moon mode :) With the tail cap switch installed, it is not an issue.


I measured throw at 10 meters, & also took a back-to-back measurement with my stock K50v2.

K50v2 measured a calculated 871 meters.

Courui measured 1166 meters.

Not bad for an afternoon's work! :)


A couple of quick mouse-overs between the Courui & K50v2 to show the difference in beam pattern. Distance is about 15 meters. (Mouse-over for K50v2)

The hot spot is small, but searingly bright. Longer distance shots would do it more justice.

Very nice mod. Thanks for sharing. I’m going to guess this will be something that a lot of people will do.

One afternoon?!! This would take me a couple of weeks, LOL. Most of them trying to find stuff, I’m just not very organized.

Very nice mod BTW.

I do wonder how much current that clicky switch will allow. I imagine it would limit it a bit.

Great contribution…Thanks

Love it. It must look like a laser beam in the fog.

Beamshots please :bigsmile: :beer:

good work!

i like the tailswitch!

can you meassure the Apms over the switch please?

Thanks for sharing this FmC! :slight_smile:

I think what I will be doing with my Courui is to ‘shamelessly copy’ this procedure. :stuck_out_tongue:

Thanks for this, keeping an eye on anything courui at the moment - if mine ever gets shipped, 4 days later they are asking me for a few more days!

nice mod thank you for sharing , any chance of Beamshots ?

Thanks for the comments :beer:

@ Pulsar13; The Omten switch is actually pretty good, djozz did a good job of trying to fry one recently in his switch testing.

@ JaredM; I’ll try to get some comparative beamshots up, but my camera is lacking the manual settings to do it well.

@ M4D M4X; Just for you, I took a reading without the battery tube & switch assy; Jumping a 25r through the multimeter showed a little over 4.5a. Obviously the meter eats up a little current, but it’s all I have to measure it.

I will not be far behind you on this…haha. A new frontier for me

A wise decision bro! Modding flashlights is a gratifying experience. And the good thing about being in BLF is that the people here are always willing to share what they know. :slight_smile:

Very, very sweet! Congrats.

I have noticed this willingness to share and the gratification posts by our generous members here since I joined BLF. Right on, bro. :beer:

Updated OP with beamshots. Sorry about the short range.


That much throw for such a relatively small amount of total expense? It’s crazy, I would say.

Very nice pics, btw.

very nice work FmC :beer:
what numbers do you get @ 10 m?

Very nice. I particularly like the tail switch. :slight_smile:


Somewhat short of 1 million, I’m afraid to say :wink: