Petzl DUO caving light modification

Had some progress with the body today.I cut 4mm aluminum I had at home to the shape of the internal space of the light in order to have some mass to absorb the heat and conduct it to the rear end where I will place the heat sink.


Cut cardboard templates


Saw it using a Jigsaw


First I glued it in place with heat resistant RTV


Then I glued it with headsink plaster


And clamp everything together till it dry

I use the hide glue because it cleans up very well. The waterproof wood glues can appear to have the squeezed out glue cleaned of completely but sometimes when one clear coats (or stains) you see a difference in coloration where there was a dried and near invisible film of waterproof glue. It doesn’t always become apparent until too late, after clear coat has been applied.

A water proof wood light might float. Could be a cool idea. Maybe I’ll have to think about that one. Include a motor and propeller/fan that could cool it in air?


I spend a lot of time waiting for wood glues to dry.

A bit more progress today:
I had to file the heat sink so it fits to the roundish shape of the light and the helmet and also to add small piece of aluminum to fill a small gap left a the side of the light


Using the cardboard technique to find the correct shape for the heat sink


Fitting the aluminum piece for the small gap


Gluing everything with thermal plaster

And waiting....

:+1:

After the Heat sink plaster cured, I did s bit more sanding to fit it perfectly to the helmet mount (had to leave a small gap to allow airflow to help with cooling.
I also drilled the place for a 12 mm waterproof momentary switch


Then, I drilled a hole for the switch wires (winch I forgot drilling before gluing :facepalm)


And (as promised) sealed all gaps between the aluminum and the original body with glue to maintain waterproof

That heatsink looks nice, definitely better than only plastic.

Good job with cutting and squeezing in the aluminium heatsink parts. :+1:

Good to see progress.

I’ve been stalled.

I took a break from working on the body and moved to the battery box.
Although the body is more interesting, the real challenge for me in this build is the battery box since it was designed for 4*AA batteries and the it is really hard to squeeze bigger 18650 cells into it.
another problem is the contacts, since I want to use 3.7V, one contact have to be placed on the lead and I have to find a way to wire this contact to the bottom part. I really have no Idea how to do it without risking with contacts or wiring problems.

Anyway, the first step was to remove all the old AA parts. Because the plastic structure is deep and none of my tolls was able to remove all the old parts and make place for 18650 I had melt the plastic at the bottom of the box using my old soldering iron (did it in a well ventilated place to avoid birthing melt plastic :) )


Original AA contacts


After melting the bottom parts


Not enough place for 4 cells

This project is up my alley! I’ve modded/retrofit l9ghts from incandescent to LED and it’s not easy so great job so far. For the batteries have you considered using 14500’s? They are not as high capacity as 18650, but you can use them in parallel for more capacity. Or just use 3 18650 unless you need series or series/parallel.

Imagine 8 × CR123As… :laughing:

(16mm, not 18mm.)





Thanks Guys.
I have chosen 18650 cells for few reasons:
First, I have tons of 18650 from old laptops so it is practically free.

But more important, in caving we always carry 2 or 3 lights for backup and spare batteries for each light. So it is easier when all lights are running the same battery size so I only have to carry one type of cells.
Single 18650 headlamps are very common and I have few so it make sense to use 18650 for this light too. It also allows me to borrow cells from friends in the cave in case I am running out of cells
It is also the reason why I chose no to use 1S2P pack that can solve a lot of problems and make the built a lot simpler.

Nice, “planning to change EVERYTHING”. Looks like an epic modification :person_with_crown:

Building a boat, are we?


Tanks PP, everything but the host :)


We should have a Budget boats forum

A bit more progress today with the battery box today,
I decided to use only two 18650 in parallel so I will have space in the box for wiring and the cells will sit in the center of the box to keep it balanced.
Two decent capacity cells will last a whole day of caving on low (~150 lm) to medium (~300 lm) brightness with short periods of Turbo (~1000lm).

Placing the springs at the bottom of the box (and not on the lid) will pop the cells out so I guess it will be easier to changes cells.

First step was to create a template for the lower board


Than to copy it to the Prefboard (on the right is the prototype :) )


And cut and solder springs


I know that many BLF members are bypassing the spring but since my "Turbo" is only 2.8A, I decided not to use bypass.
Next step is it the wiring, I have some Ideas how to connect the contacts on the lid but still not sure what is the best way

And if that 2.8 amps is supplied by two cells in parallel it is only 1.4 amps per cell. IMO, you don’t need to bypass the springs.


Exactly what I am thinking :)

Didn't have a lot of time today so I only made a small progress with the battery box wiring.

I decide to use screws terminals (not sure if it the correct English term, in my language we called it chocolate connectors since it looks like chocolate table :) ) for the wire connecting the battery box to the lamp.
The reason I prefer screws over soldering is that most caving lamp issues are related to the cable and using screw will allow some troubleshooting "on the field".





The black wire is for the negative pole on the lid but this will be explained on the next update...

As promised, today I made the wiring from the power cable to the lid.
I considered many option and the two best option IMO were:
1. A dummy cell to conduct between the bottom board and the lid.
2. A wire (with or without connector)

I decided not to use a wire since I am afraid that frequent battery changes may cause contacts issues along the cable or at the soldering points and as a primary caving lamp I need to be super reliable.

For the "dummy" cell I used an old piece of Polypropylene I have from another project


I cut and sand it to fit inside the battery box with a small groove for the 18650 on the other side.

The top part had to be smaller to allow closing the lid


After a lot of hand-sanding it fits perfectly :)
You can also see the drill for the wire at the center


Currently I am planing to only use a single dummy cell and use some kind of foam to support the cells from the opposite side since:
1. It is lighter
2. It is less work :)
3. A foam will prevent the cells from rattling in the box.

:+1:

Looks good to me.