COURUI Conversion: Parallel to Series ~ "My Way" ~~~ Heat Sink Finished ~~~. Mod Finished ..."Really Finished"!!!

There are bits and pieces of modding Q&A on the COURUI thrower scattered about various threads, so I thought I'd start a new one on a series battery conversion.

Members are finding the stock driver lacking, and most of the options require a series setup. I hear lots of talk about series conversion, but I haven't really seen any tutorials. Having never done this before, I pondered the idea and came up with this solution.

I forgot to take a photo of the tail before I started, so I borrowed this one from LinusHofmanns COURUI thread.

Other than the LD-36, most of the larger buck drivers cant function with an electronic switch so a mechanical (clicky) switch needs to be installed. If you don't need the tailswitch, just leave the wire bridge as it is. Even with a side switch , a tailswitch is great for lockout.

I used a Solarforce P60 switch because it was handy, and it fit. I just soldered onto the existing wire bridge pads.

Cut the trace so only the first cell connects to the switch. This will be the first cell of the series that starts at the switch. A DMM really helps to check things for connectivity.

On the reverse side I removed two of the springs and added a shorter spring and a copper pad. The long spring is for the cell that will make contact with the driver Batt+. The small spring is to make the finished assembly easier to screw onto the head. It will explain itself in the final assembly.

Next we work on the driver end of the body. What you see in the next picture is not copper, but PCB circuit board. Yes, the same material that your drivers are made of. This board has copper coating on both sides that will be mostly sanded off.

Okay, what the hell is that weird shaped thing? You'll see in a minute.

I cut and filed the board into my required specs. and sanded off most of the copper cladding, leaving enough to bridge the +and— terminals. I soldered on another copper pad and a short spring.

Here's the other side. I had to sand off all the copper.

Let's see if this baby works. Batteries are required.

And now for that weird shaped thing I made.

Look at that. It fits like a little hat. When the body is screwed into the head, the exposed cell will make contact with the BAT+ of the original driver (which I intend to use as a contact board). I could always make a new contact board using my copper clad PCB circuit board.

...and for goodness works?

I couldn't test the light out because the 4.2v driver is still installed, so I covered the contact board with paper and threaded the body onto the head.

With three Protected 3400 Panasonics everything felt snug with nothing rattling around inside.

Getting back to the tail switch. I still need to drill a hole in the end to fit the rubber boot. I couldn't do it today because I don't have a big enough drill chuck. My neighbor is lending me one, so hopefully I can complete it tomorrow.

The boot should fit in here nicely without interfering with the lights ability to tailstand.

To be continued

It's tomorrow, and it's time to finish the tailcap.

Let me first mention that if, like me, you don't have access to a workshop with drill presses and such, you have to be prepared for and expect problems. I decided to record the things that are encountered when working with basic tools at my kitchen table.

I started out by drilling a small pilot hole from the inside of the cap. There was a nice machining dimple in the dead center which made centering easy. Next I used a larger bit to countersink the hole so the large bit would would center without walking away. I don't know why, but I find that large bits always move their center to one side. Perhaps it's the tork. Anyway, as expected the hole was off center.

The bit was old and nicked up, and jammed before it went all the way through, but that was probably a good thing. This is where patience comes into play.

I knew the bit was not as large as the rubber boot, so having to switch to a grinding stone and rotary tool was expected. From the inside, I marked where I didn't want the hole expanded any farther, and concentrated on opening it up in the opposite direction.

The grindstone became clogged with aluminum, but there's nothing to be done about that. Just take your time, checking for fit regularly.

The hole finally fit the boot. I used I small sanding drum to clean off the burrs.

The boot fits, and it works!

Although the boot works fine as is, I had some plastic bits in my box that came with SolarForce switches. I found one that I liked the fit of to help keep the boot firmly supported. You can probably find some sort of washer that fits in your junk bin, or make one from some plastic. It can be any shape, you just need to drill a hole for the button.

I must say that I'm very happy with the results. The cap is slightly off center, but I'm the only one that will notice. Other than that it looks very professional.

And it can still tailstand!

To be continued.

Next up: Improving the heat sink.

I cut the copper for my heat sink.

Next I coated the threads of the aluminum emitter plate with Arctic Silver and cranked it down tight to its ledge. Then I mixed up some Fujik with copper fairy dust and coated the underside of the emitter plate and clamped down the first copper disc.

I let it cue for two days.

I coated the underside of the cooper round with solder paste, inserted the copper collar and hammered down the smaller disc to force the collar against the wall of the pill.

...and added heat.

Drill a hole through the center of everything. My pilot bit snapped off, and trying to get a new hole started left me off center. That doesn't matter though.

Another copper round was clamped down with copper fairy dust adhesive.

Next I need to solder in a copper plug which will unite all the components and spread the heat evenly.

Here's a diagram of the whole heat sink.

Strip the stock driver to use as a contact board.

Add a 7A driver

I installed the reflector, lens and bezel, tested the driver using two cells. Good to go.

...and disaster strikes, and strikes hard!!!

All I had to do was screw the body into the head and click the switch, but noooo.

I had screwed the body and head together lots of times and always noticed that near the very end it felt gritty. This time when it got to the gritty part, it ceased. It would not go forward or backward, just wiggled back and forth 2mm.

I worked for two days trying to get it apart. I tried everything, clamps, vises etc. after giving up on trying to be neat I resorted to vise grips, hammers and chisels.

I knew in my heart it was never coming apart, and I wanted my driver back so I sawed the damn thing in half with a hacksaw.

Win some, lose some.

I have another COURUI so I'll probably try it again, but not right now. It would be too much déjà vu All over again.

very nice Ouchyfoot, ill be adding info/questions to this thread once mine gets in :slight_smile:

I take my hat off! :face_with_monocle:

Everytime I see mods like this, I get a little bit frustrated because my own modding ideas keep struggling with reality, my budget and pure non-talent of mine.

On the other hand I learn a lot by just reading these fine mod threads like yours.
Keep on the good work.

Thanks nikanon. I’ve been playing with this in my mind for a while. It’s always nice when things work out the way you imagine them.
Next I plan to go for 4x18650 in series. The part to overcome is that the last battery always has the negative end facing up.

Hey, that looks like the old half moon on the outhouse door.

Seriously, great mod and very inventive!

This is really great! Although I do not own a Courui yet but if I happen to have one I am going to mod it into series configuration. Going for buck regulation is the best!

Very nice! Ever since I've converted a few ZY-T08s I've had the itch to do something crazy like this... maybe the SRK is the next on the chopping block!

Thanks again, Ouchy. By the time I get around to playing with my Courui most of the mods will have been documented already! :beer:

The tailcap is finished! Modding details and photos added to the OP.

Very nice work on the tailcap switch and conversion, I’ve been tempted to do something similar but just for the easy lockout possibility while keep the battery configuration and side clicky. I’ve blinded myself too many times to count getting used to that sensitive side clicky! :wink:

I’m not an expert when it comes to machining but I had a similar task on my BTU and couldn’t risk drilling off center. I used something like this ” conical drill bit”:Shop by Category | eBay

Even using a hand drill I managed to get a nice and centered hole perfectly round with much less wandering than if I had used a similarly sized normal drill bit. Might be worth considering next time.

Is there really no driver option available that supports the side switch?
Seems such a shame to bypass one of the great features of this light just to get regulated output

Just saw your other thread, you’re using the ld-36 driver?

Thanks Linus.
I’ve been looking for a 3x18650 soupcan for a while just to see if my idea for a series conversion would work. I also have scads of 4P lights, and needed the change.

I plan to install a 7A buck driver for no other reason than I’ve never run a single XM-L2 over 5A before. I don’t know what will happen. It seems like a waste of space just having a single board driver in that big cavity.

I’m in the middle of redesigning the heat sinking on the pill. I’ll be posting the build and photos in the OP.

I did order an LD-36 driver. I also ordered another COURUI (in case I wrecked this one), so it may go in that one. I’d install another tail switch just for easy lockout.

Thanks for the bit link. I’ll be seriously looking at them. I guess you have to keep stopping the drill to take measurements. I also took notice of that reflector you installed in your COURUI and ordered a couple.

Yeah I actually had one without the stepping so I just drilled until I got to the right size, the steps should be known diameters so that should actually be easier. I think what helps is the cuts are gradual and the previous step acts as a centering hole for the next cut. They’re also perfectly round except for where the cutting edge is recessed so I’m sure that also helps avoid wandering compared to helical drills.

You mean the acrylic lens right? I’m still really impressed with mine so hopefully you will be too, no scratches yet either ! :slight_smile:

i wish mine will get here all ready its been over 4+ weeks from KD, if i go this route like Ouchyfoot did i will not use the rubber boot, ill have a little piece of aluminum machined to fit the hole ?

Very cool, I’ll keep that in mind when I get my driver in.

Ouchyfoot do u mind if i post a pic or 2 of my switch ?

Knock yourself out Nitro.

PS: I got my second COURUI. Eight days from day of mailing. My first one came real fast also.

true luck there it took one of mine 41/2 weeks and still waiting on my other

judco switch :slight_smile: 10 amps >)

how thick the button it

and how far it sticks out as shown on the right

Also im going to the harware store and im getting a stainless steel washer and im going to place it around the click switch to cover up the little hole showing

Impressive work Ouchy!

Looks like a great mod!

Ill be following this thread.


Nitro. How far does the switch extend inside the head? Do you have a link for the Judco?

its about 10-13mm from the inside but this is what im going to do for my heatsink

the heatsink will slide in and it will keep my switch cool as well, and it will be set in place by a set screw

and i used this