Thought that IMR batteries were "good"? Can they burn out tailcap?

LED Flashlights – General Info
1

Hi,

A bit of a long story…

Still new, so earlier, I was reading (don’t remember where) that IMR batteries were good, because they could supply high current(?).

So anyway, I found some on Ebay recently, and picked up several.

As I said, I’m still new/learning, and I had been trying for awhile to try to use a rechargeable battery in a “TechLite Lumen Master 250” that we got from Costco, in place of the 3xAAA carrier, and, in particular, an 18500 for the added capacity.

I had some problems the 1st try, apparently due to a bad 18500, so I just got a new IMR 18500 in today, and put it into the light, and it worked fine.

So, I figured I’d leave it on high, to see what kind of runtime I’d get.

Awhile later, I noticed the light was off…. Oh, oh :(….

Removed the 18500 and checked the voltage and it was good, so let the light sit, then put the 18500 back in, but still wasn’t working.

Put the original 3xAAA carrier in, and light still not working.

At that point, I figured that I’d fried the light.

But, I guess I’m kind of stubborn, so I happen to take the tailcap from another same light and put it on the apparently dead light, and VOILA, it worked!!

So, it looks like I killed the tailcap??? I didn’t think that was possible? Isn’t it just a mechanical switch?

Also, I’m theorizng that using the IMR battery may have been a bad idea, i.e., because it can source higher current (vs. 3xAAA or a “normal” protected 14500 I had tried earlier this week) to the light, maybe too much current, such that it fried the tailcap/switch?

Does that make sense?

Also, I haven’t done much disassembly, but is it possible to fix that tailcap/switch?

Thanks, and sorry for the longish post.

Jim

P.S. Thank goodness these lights came in a 3-pack :)!!

2

Your theory is probably right on. The current provided by an IMR is going to be FAR higher than the current provided by a 3 AAA Alkaline Cells. The Tailcap switch was designed to handle the current provided by the (intended) 3xAAA Alkalines.

The only way to know if the tailcap can be repaired is to take it apart and see what cooked in it…

PPtk

3

Hi,

I’m trying to figure out how to disassemble the tailcap?

I found this:

and I can see the whitish plastic ring with 4 notches (at 90 degree intervals), but I can’t get it to budge with a needle nose (per that thread). Tried to turn it with a flat screwdriver which didn’t work either :(…

Any ideas? Do I need like a spanner wrench or something (don’t have one of those)?

Thanks,
Jim

P.S. So was getting/using the IMR batteries a bad idea, in general? Or, just because of this light?

4

Hi,

I got the switch assembly out!! Needle nose didn’t work, but the buckle of one of my watchbands was just smaller than the diameter of the tailcap, so I used that to push the spring down, so that the buckle went into two opposing notches, and I was able to (slowly) unscrew the assembly.

However, the assembly seems to be all one piece? I can’t seem to take it apart like in the image on that other thread.

I’ll post some pics:

Does anyone know how to disassemble that?

Jim

5

I was able to take the switch assembly apart, but, visually, everything looks fine:

Nothing looks “burnt”. The chip looks ok, and solder joints look intact.

Jim

6

Also, I shorted the battery negative to the threads, and the light does light, so it’s just the tailcap switch that’s the problem.

Re. the cause of the problem: Looking back at this thread:

where it says:

“Current regulation is via the internal resistance of the AAA batteries”

I’m guessing that since the IMR battery has lower resistance, there wasn’t any current regulation.

But seeing that there’s no physical damage to the switch PCB, I’m guessing that the switch itself may’ve been fried?

Jim

7

No, that small tactile switch is used to control an electronic switch… which is probably fried.

8

Hi,

If it is the electronic switch, and not the physical switch, then in post #5 of that older thread I linked above, there’s description of removing most of the components on the switch PCB, and getting a single mode light.

If I did as that post describes, do you think I’d be able to revive this light, albeit with just a single mode?

Thanks,
Jim

9

Hi,

Comparing the images I have in this thread above, I was wondering if maybe I could replace the original switch with a McClicky switch, like this:

https://illuminationsupply.com/mcclicky-switch-p-62.html

That says that it’s ok up to 6A@12V, so maybe that would prevent the switch failure that I had with the 18500 battery/current?

Has anyone adapted a McClicky to something other than a Surefire?

I know that this switch costs more than the light, but….

Thanks,
Jim

P.S. A better picture of the switch:

10

If you can find or adapt a mechanical switch, it should work fine. Modes are probably controlled by the driver. You should be able to test them by shorting the negative to the threads (as when you measure amp draw) with quick movements to replicate a half-press to the switch.

Didn’t see above - have you measured the sustained amp draw of the 18500 IMR in the light in high mode?

What is the draw with fresh primaries in the carrier?

11

Hi,

I found this video:

which “inspired” me, so I went out to a local Microcenter, and they had some 9-LED lights for $2.99 with tail switches, and picked one up (funny thing is that one of them had the rubber boot removed, so I’m guessing someone else was looking to do something similar).

I just got that done, and WORKING, but things weren’t the same as that video.

I think that video was for an older version of the Techlite, whereas the ones I have are the 250s.

Also the switch that I pulled out of the 9-LED light was different… it was kind of encased in a thin, cylindrical assembly, and wasn’t disassemblable (not sure if that’s a real word :laughing:.

So, what I did was:

  • Remove all the parts from the Techlite tailcap
  • Take the switch assembly from the 9-LED light and file a bit around, because it wouldn’t fit into the Techlite’s tailcap.
  • Put the original boot back into the Techlite tailcap
  • Shove the switch assembly from the 9-LED light as far down into the Techlite tailcap as I could. Actually, I had to use a screwdriver and mallet to force it down far enough, so it’s in there to stay. I was hoping that I’d be able to just thread it into the tailcap but that attempt failed.
  • Disassemble the original part from the Techlite with the 2 clear plastic halves and the PCB. I only use the top plastic piece to screw back into the tailcap, to hold the switch assembly from the 9-LED light in, and also to provide the spring contact for negative. Also, I had to clip off the two “ears” from that piece that were used to join it to the bottom plastic piece, because they prevented me from screwing it into the tailcap.

That’s it!!

Now, the light works with a 18500 battery+magnet.

However, I only have 1 mode, “high” (no strobe and no low).

I understand what you said, but I think that, in this light, the PCB that was in the original tailcap is what was providing the modes functionality.

Here’s the PCB from the original Techlite tailcap (I’m assuming that the chip is an MCU?):

Here’re some shots from the assembly:

The 9-LED light (thought the pink one was nice :laughing::

The Techlite tailcap with the switch assembly from the 9-LED light “installed” (=“crammed”) and the modified top plastic piece from the Techlite tailcap:

The modified tailcap, the Techlite, and the 18500 battery+magnet:

IT WORKS :)!!

Jim

12

GottaZoom,

I forgot: I haven’t tried to measure the current yet.

Also, I’m still planning to try to put that McClicky into the tailcap, when the new switch arrives. Does the McClicky have the “smarts” to provide modes, or is it just a “dumb” switch?

Jim

P.S. With the switch from the 9-LED light in the Techlite, I do have momentary/half-press, but the light just “blinks” when I half-press… no modes/mode changing. In the video I linked, that fellow seemed to still have modes after swapping the switch, so I’m assuming that with the older lights, the mode functionality was not in the tailcap (but it appears to be in the tailcap for the 250)?

13

that switch pcb does look suspiciously like a driver, I would guess to get modes you’d have to look at squeezing a driver in the head.

nice work on getting the switch sorted though, I’m thinking that at the moment its a nice little direct drive light.

I would suggest stripping the head to assess whether you have some space for a driver (you’ll probably have to make a pill from copper plumbing parts.

I would also suggest that when/if you order the driver, order another driver, emitter and host and build one up, I think you’ve had fun here and I think you’d have fun with a diy host too. 8)

14

Hi,

I’ve read that a strap wrench, which I don’t have yet, is needed to get the head off, so I haven’t tried that yet.

In post #5 of this thread, Modding the TechLite Lumen Master (aka the Costco Special Cree Flashlight), there’s a link to an image of the LED (in the head?), I think: http://i.imgur.com/i5uPxAL.jpg.

Is the design of that techlite, where the “smarts” is in the tailcap, rather in the head, an unusual one? At least from the various reading that I’ve done so far, it seems like it is?

Jim

15

it seems odd, generally the driver (assuming the components on the switch pcb are a driver) is in the head just behind the emitter.

16

Hi,

Thanks, that’s what I thought (just from reading). Unfortunately, there aren’t any markings on that chip, otherwise, I could try to identify it.

Jim

17

Congrats. Sounds like you are running direct.

I wouldn’t expect the other switch to have a driver.

18

Hi,

This may be taking this off-topic a bit, but I’ve been thinking about “the design” question more, i.e., the question of the location of the driver, in general.

It seems like, having the driver in the tailcap (as opposed to “up front, in the head”), might have some interesting implications, in particular with providing opportunities for thermal management.

I haven’t “been around” the “modern” flashlights for very long, so I don’t know “the history”, but I was curious if this approach (having the driver somewhere else, other than in the head) was something that flashlight manufacturers and designers had considered, but then dismissed a long time ago? And, if so, why?

Jim

19

Hi,

I haven’t put much thought into it, but what I meant by “providing opportunities for thermal management” is that, logically, with the driver and emitter in the head, you have two sources of heat, concentrated in one small space, whereas if the driver and the emitter were in different places (in the head and in the tailcap, respectively), you have them separated, and could possibly do a better job of thermal managing both?

Jim