I bought two CPFItalia Cometa flashlights. Like you, I was disappointed to learn that a small number of these flashlights have dangerous defects that can cause a direct short-circuit of the battery.
There are three issues that I am aware of.
First, is the one you wrote about. With some batteries, it is possible for the positive battery contact to touch the retaining ring on the back of the pill. When this happens, the battery is short-circuited. Flat-top batteries are the biggest offenders.
The simple fix is to cut a doughnut-shaped piece of plastic that fits around the spring at the positive end of the battery. That allows the battery to touch the spring, but prevents it from touching the retaining ring. I made mine from the plastic lid on a microwave-safe tray for hot food. It is a disposable plastic container used by the deli of a local supermarket. I figured it would be better able to stand heat than other plastics I had around.
Now that I am writing this up, I think I should go back and make another insert that does not have a hole for the spring. I would like to test, and verify that the plastic is doing its job as an insulator. If the flashlight won't work at all, then I can cut a hole for the spring.
The 18650 sleeve that comes with the Cometa makes a good template for drawing a circle of the right size. I used scissors to cut mine out, and an "Exacto" knife to cut the center hole. I believe that some have used a drill to make the same cuts.
Several BLF members report that the seller Banggood, upon request, has sent them a plastic disk for this purpose. I have not done that. As yet, I have not made any request of the seller. I am holding off on that until I make a final decision on just what—if anything— I want from the seller.
By the way, the first sign of trouble is when you insert a battery and discover that the tail cap won't light up. If that happens, unscrew the tail cap immediately!
The second issue with the Cometa concerns the black, parabolic disk that screws in over the emitter. It has a hole for the emitter. The black surface prevents internal reflections in the flashlight head that can cause artifacts in the beam. By artifacts, I mean rings, dark spots, and so on.
In most Cometa flashlights, the disk works fine. It screws in above the emitter board, without touching it. In some Cometas, however, the disk rubs against the solder joints that connect wires to the emitter board. The disk is anodized, so it is an insulator, but it only takes a small amount of abrasion to scratch through the anodization.
If that happens the disk can become an electrical pathway to ground. When the positive lead on the emitter scrapes through the anodization, it creates a short-circuit from the driver output to ground. That is a dangerous short-circuit.
A lesser concern is what happens when the negative lead from the driver output is short-circuited through the parabolic disk. That does not cause dangerous short-circuit, but it will cause the driver to temporarily stop working. The flashlight then becomes a direct-drive flashlight that only has one mode, the turbo mode.
Although several owners have reported scuffing of the anodization, with some including photos, as far as I know no actual short-circuits have occurred through the parabolic disk. It is, nevertheless, a problem that needs to be addressed.
Several fixes for this have been proposed. All of them involve insulating the parabolic disk from the emitter board. Those with soldering skills have also flattened the solder joints where the wires are attached to the emitter board.
As yet, I have not implemented any of these. Nor have I attempted to unscrew the parabolic disk. In my case, I inserted a plastic disk at the positive end of the battery, and then verified that the tail cap was lighting up. Next, I briefly flashed the light on and off several times. As it correctly powered up in moonlight mode, I surmised that there were no shorts.
As a double-check, I quickly ran through all the modes, from low to high. When I was done, I took out the battery, and checked to see whether the tail-cap spring had heated up. Overheating is a sign of a short-circuit. Be careful touching the spring. If it is overheated, you can burn your finger. Finally, I ran the light on high for a few minutes, and then checked the tail-cap spring once again.
These tests may be insufficient for long-term reliability. Eventually, I plan to install another insulator between the parabolic disk and the emitter board. At present, I am waiting to see how things settle out. The seller may eventually offer free fixes of its own.
The third problem with the Cometa is the diameter of the emitter board. It is not quite large enough for the shelf in the pill where it sits. This makes it possible for the board to be improperly centered when it is installed. The close proximity of the wire connections to the edge of the board can be a problem in some flashlights. If the solder blobs are large enough, and the emitter is off-center, one of the blobs can touch the edge of the pill. If the positive connection shorts out, you get the same dangerous short-circuit described above. When the negative connection shorts, you lose flashlight modes, as described above.
When the emitter board is off-center, it is also more likely to rub against the parabolic disk as described above. That's because the disk has a nipple at its center that protrudes down towards the emitter. When the emitter board is not centered, one of the two solder connections will be moved closer to the nipple (while it's opposite member is moved away). This can lead to scraping between the solder joint and the nipple.
Enough with the problems. Last night, I took both of my Cometas outside, and had some fun with them! Beam intensity, when my neutral-white versions are focused, is probably around 150,000 candela. That is a conservative guess. I have not measured. If right, however, that would convert to an ANSI FL 1 beam distance of about 775 meters. Compare that with the 900 meters claimed in the spec when you buy the Cometa with a cool-white emitter.
By the way, I usually divide FL 1 beam distances by a factor of 4 in order to get the distance at which my tired eyes can make out a distant object. That gives the distance at which 4 lux fall on the target. Others here divide by a factor of 2 or 3.
Whatever factor you use, I can report that the Cometa throws a long way! Besides the BLF Kronos X6 and the ThorFire C8s, both of which are 1x18650 compact throwers, I do not own any dedicated throwers. That makes the Cometa the longest throwing flashlight I own. Equally impressive is its unfocused beam. It is super wide, just what I like best about zoomies.
Here is a YouTube video that shows how to dismantle the Cometa. Thanks go out to BLF member Jeansy for posting it.
DISCLAIMER: I have described the things I did with my Cometa flashlights. I am not a flashlight engineer. I cannot guarantee that the things I did are safe or that they will work for you. Any repair you undertake with the Cometa is AT YOUR OWN RISK.
