Fenix HT18 and How Do Flashlights Determine Battery Type?

[Alex2]

Hi,

It's my first post here!


I initially started this thread to compare the Fenix HT18 and the Acebeam T28, but I've since managed to answer most of the questions that I had about the Fenix, except for one, and also decided against the T28, so I've decided to edit my original post to reflect this, and added the info that I found out, in case it helps anyone. Also, if anyone can answer my final question (bottom of this post), it would be much appreciated.


Questions with answers...
- Is there sufficient clearance in the battery tube for 21700 cells with an external diameter of 21.8mm? I believe the included cell is only 21.5mm - ANSWER: yes, apparently the internal diameter is 22.05mm.


Questions with some info...
- Does the USB-C port on the included battery support charging using a USB-C>USB-C cable, as opposed to the included USB-A>USB-C? INFO: I haven't, as yet, been able to answer this for certain. However, I believe I am right in saying that the Fenix PD36R is one of the only lights that can be charged using a USB-C to C cable, so it seems fairly likely that, as another Fenix product, this battery may also be able to be charged in such a way, but I can't say for certain. I will update here if I find out for sure.


:shrug:Remaining Question...
- Apparently the light runs at a lower turbo output when using 18650s. How does the light know what battery is inserted (is it just via voltage sag on the smaller cell)? Basically what I'm trying to find out is if I'll have any problems reaching the full turbo output using (good quality) non-Fenix branded protected 21700s.




Thanks!


Alex.

 

[Alex2]

Re: Fenix HT18 or Acebeam T28

Deleted as original post altered.

 

[Alex2]

Re: Fenix HT18 or Acebeam T28

Deleted as original post altered.

 

[Alex2]

Re: Fenix HT18 or Acebeam T28

Update: I've altered my original post as I've been able to answer some of my questions.

However, I'm still not sure how the HT18 detects that an 18650 is installed, as opposed to a 21700, in order to reduce its turbo output. Does anyone know how this could be achieved? Is it via measurement of cell voltage sag under load, or some other method?

Thanks!

 

[CarpentryHero]

Re: Fenix HT18 or Acebeam T28

Looking at the specs and what comes in the box, it looks like they designed it to get the same max runtime on there respective 18650 and 21700 that they sell.
i can't say for sure but the easiest way to make the light know which battery you are using, is that it can detect the sleeve adapter used for the 18650

that way you get the 1.4 hour turbo with both cells, I tried checking YouTube to see if anyone started it up on an 18650 with no luck, if it gave an initial 1500 and then bumped down after then it's using voltage sag to determine the battery inside. Fresh off the charger it shouldn't be able to tell, then an imr cell would still achieve the 1500.
Once an 18650 is detected it could remember the cell until it's taken out and put back in, I've seen that before.
which makes me think the easiest way would be to design the battery sleeve adapter to be detectable within the light

 

[Alex2]

Re: Fenix HT18 or Acebeam T28

Thanks for the reply!

I did wonder if it had something to do with the adaptor. However, I've looked into this, and it seems there's no special set of contacts for the adaptor or anything like that, and the adaptor is just a tube with a spring in it and a button top! However, I'll be receiving an HT18 soon, so I'll update here once I work out how it's doing it!!