Water Cooled Flashlight Modding a MT35 PLUS RE-MODDED

I am going to do a mod that will take a few weeks to finish the first of 3 mods to the same light. Is the featured mods the correct place to start this thread ? Thanks :beer:
EDITED 01/31/2021
I was not satisfied with the finish, so now its better. :smiley:
Also, after burning some leds and 20mm mcpcb’s, it was necessary to upgrade to newly available 32mm mcpcb that required some work.
Latest mods.

GOTO #78 for last update.

I am a newbie here to Lithium powered flashlights and BLF. So you will see many missteps and screw ups and please let me know so the error will not be repeated. When I first found BLF, I was so happy to see all you good people helping each other, I wanted to join and try to contribute something. So after buying a MT35 PLUS and using it, well it would shine far but not bright. Looking to mod it we found this https://budgetlightforum.com/t/-/48040 and the idea was born in this thread. This will be a 3 part build. Part 1 will be to design and build a water cooling system with pump using a 12v 7amp driver from Lexel to power the pump and XHP70.2 led. If the cooling is successful then proceed to Part 2 which is an upgrade to a CTF-90 and 40 amp driver. And finally part 3 which will be adding the Aspheric lens http://www.optolife.com/singlet_lens/A380.html. The reason for not going to the CFT-90 first is we didn’t think it could be cooled, even with water. So here are a few pics of the progress so far.







Interesting project. The copper heat exchanger looks really cool. How do you plan to move the heat from the water to the air?

Why do you want to use an aspheric lens? It will increase throw by a bit? Light collection efficiency of a lens like this is only 25-30. Whereas a reflector puts 70+ of the light into the beam. If you really want to use a lens I might consider using a precollimator lens which can double the light collection efficiency.

Holy smokes, this will be interesting.

Looks great!!

How will the pump be mounted and where?

Cool project :THUMBS-UP:

The pump will be externally mounted somewhere, I have not tackled that one yet, but somewhere opposite the button switch.

Nice project! What rads do you plan to use for cooling?

The heat will be displaced from an aluminum coil mounted around the head, but no fan for that.
I wanted to have it zoom-able for flooding and throw, not sure how effective it will perform for either one until its finished.

1/4 in diameter soft aluminum tubing wound around the head 2 times with .100 in gap between coils. No fan.
I have been trying to learn from your builds so we all kinda work together and share. :beer:

The coil is in work to get finished this weekend if everything goes as planned.
Using the head for the mold.

How much heat (W) do you want to dissipate with the coil? Build a few watercooler for CPUs and Motherboards myself a few years back. And also build a lot of custom cooling solutions. Interested to see how you fit it together.

Is that like 25ft of coil?
Should definitely be enough for a CFT90 as long as you don’t do more than 30-40A

“TheOnlyDocc” Sorry, I’m not able to know the amount of heat except from reading and guessing how much trouble
everyone is having with thermal step down after a few minutes run time. I’m not sure this idea will work at all, but I could not
resist the opportunity to try and maybe throw some information into the hat for everyone to use.

“Enderman” Yes it is a 25ft roll. Trying to squeeze as much as possible on it and not take away too much flashlight appearance.
I have yet to solder the spacers in place and form it into shape. I will give the total feet used for reference so the guys who know how can do those if we can give them accurate info.


Aluminum soldering proved too difficult so small stainless steel wire was used to assemble cooling coil.


More pics next week. Still a lot to mod before completion.

Interesting, Keep up the good work!

Epic build :slight_smile: Will be following this 8^)

I noticed that you are using copper and Aluminium in the same loop. This will get you corrosion fast. Had the same problem in a PC watercooling loop. Even with very high quality additives. It takes longer but eventually it happens. And the solderjoint that have contact with the water will also be a week point.

Yep , that’s a good point. I had read some on this subject, mostly for best heat transfer. Corrosion was mentioned often as a concern and freeze preventative which can lower cooling efficiency. Probably will use automotive coolant and empty the system while in storage and flush it clean, but not sure what corrosion preventive to use at flush and leave dry.

This is all a guess for me, so if anyone has a suggestion please feel free to say something, I’m just a newbie here, I can machine things but I know little about flashlights.

So, has the project been finished or not?

I’d like to know :slight_smile: