tube or battery issue? Emisar D4V2

Hello All, this is my first post from a longtime lurker, and, I want to say “thanks” to the BLF community for helping me to learn about, and getting into, hi-perf lights.

This post concerns my most recent purchase, the awesome Emisar D4V2. I’m baffled over a problem that I first thought was battery related, but, after trying both VT6a and 30q 18650 battery types, I’m now not so sure.
When fitted with optional 18350 or 18500 tubes (and 18350/18500 batteries sourced from Orbtronic) the light performs as expected. Which is to say, “wow”. However, when I mount the standard 18650 tube, along with either a VT6a or 30Q battery, things get weird: The light goes into some sort of ‘limp’ mode (my words); the software seems to become confused.
For example, the usual click sequences no longer work as expected; the output stops, or stalls, at the point of FET. In general, the software seems to have a mind of its own, even to the point of not turning off.

I have read that the D4 hotrod needs all the current it can suck, and, I’ve also read about possible bogus 18650 batteries from some vendors. So, my first thought was, ‘ah-ah’, I’ve got crappy cells. But, if that is the case, would the light work normally with the smaller 18350 and 18500 cells?

As I said, this situation is baffling me. Before I purchase and try VT5 cells I’m wondering if anyone here has some insight?
Thanks for listening.

“The light goes into some sort of ‘limp’ mode (my words); the software seems to become confused.”

This is hard to understand what is actually happening.
Have you calibrated the temperature and set the desired amount of max temperature it should reduce power?

Try cleaning the end of the tube and contacts?

Maybe post some pictures with the ends of the 18650 tube from various angles, as one can speculate a alot.

^ This. Thoroughly clean both ends of the 18650 tube, check that they have a good flat contact surface, also clean the annular contact area in the tail cap and head for good measure. That should get it back to normal.

Thanks for so many quick replies.
Cleaning didn’t do much :-\ but did make me realize that the only component I’m swapping is the tube itself, and, thus, if the light works with other tubes / batteries then… it kinda seems like its a battery issue. Which also doesn’t make a lot of sense seeing as how I’ve tried four cells of two different types. Hmm

What is happening is, with the 18650 tube and cell, the light will ramp to the first blink, which, I have read, is where the FET comes into play. At this point there is no further ramping, the clicks become irrational, and the only thing that reliably functions is to click-off. Even that doesn’t always work.

When I return to the smaller tubes and cells everything works as it should.
I’m have to think it’s cell related?

Edit: I didn’t clean the tube itself. Lemme go do dat and post back.

After degreasing and cleaning the tube… still funky stuff going on. However, the symptoms have changed at bit. And that points to something with the tube.
I’ll try another cleaning. If that doesn’t help then I guess I’ll have to contact Hank?

You do not have to degrease the tube, only the contacts. What is anodized has no electrical conductivity so no need to degrease the threads, only the exposed aluminum or the gold contacts on the PCBs since those are the only points that make electrical contact in the aluminum body.

@Hikelite, Bingo! A light sanding of the exposed alum was it. Not sure I would have thought of that myself. But, thanks to your comments I now better understand how the circuit is made.
Thanks to you, and to all, who helped.
As for the D4V2, for me it’s the coolest of my small collection.

Another thing to note, do you have one tail cap which you swap between 18650 / 18350 tubes or do you have another tail cap already attached to the 18650 tube?

Reason I ask - Make sure all contact surfaces are clean, use IPA (isopropanol alcohol) if you have it with a paper towel or just a dry paper towel.

The few times I’ve ran into quirky behaviour from a flashlight it typically stems from thread lube fouling the contact surfaces (silicon in my case). Following a cleaning and firmly screwing all components back together the issues have been resolved every time thus far.

I’ve had these typical issues with FW3A, EDC18 and a KR4. I make a habit of cleaning flashlight contact surfaces and sometimes lapping them level and burr free when new.

Edited to add - I see you’ve already resolved the issue. :+1:

Good job with the sanding of the flat surface, careful to sand flat, it is easy to sand at “177deg”, 180deg is pretty hard.
Sometimes the tubes in flashlights aren’t perfectly flat and then issues can happen, especially if they have only a thin sharp edge that does not allow proper contact, where low modes might work, but turbo might have issues and power could ramp down.
But could also be some leftover tiny aluminum piece stuck onto the contact areas that can push the contacts apart causing issues.

Thanks, again, for the help. This forum rocks.

Awesome outcome! :sunglasses: