4171 Cap Mod For 3 X CR2 Batteries!

[jayrob]

I did this simple cap mod for the 4171 host for leukoplast because he has an LM317 based driver with a blu-ray diode, and he wants to use the 4171 host because of the room it has inside to fit his module/driver combo...

Anyway, he needs more voltage for this driver/diode set up, and so I believe this 'easy to do' cap mod will allow the extra 10mm's needed (length wise) for the 3 X CR2 batteries!

I thought that this is a good thing to pass around...

Hey leukaplast, please post back here in this thread to let us know if it works. Because I did not have a (new style) 4171 host to try the cap mod out on. But I am sure it will work just perfectly.

Now for the RCR2 batteries, they are just a tad longer, so I'm not as sure about that fit. Let us know will you? (shipping today)
Jay

 

[leukoplast]

Wait, all you did to extend the length was to snip the spring shorter? I thought you were going to somehow remove some of the internals or shorten up the insides somehow (not including removing the black thing I already took out).

Before I sent to tailcap to you I had already removed that internal black thing then and popped in three CR2 batteries (primaries) to see how the fit was before the mod. Needless to say I didn't want to screw it on all the way because I wasn't sure if I was going to bend or break something because it was already pretty tight with only a few screws. But since the spring was easily compressed all the way, I am not sure if there would be any gain in length just by snipping the spring.

I was going to need another 5 or 10mm after the removal of the black-ring thing in order for three of these to fit. Well, I will know for certain when it arrives. I have a feeling in order for this to work, I will need to have the tailcap only half-way (or less) screwed on.

 

[jayrob]

It will work...

You told me that your RCR2 batteries are 26mm's correct? 3 X 26 is 78mm's overall length.

RCR123's are 35mm's each. That's 70mm's, with a little extra room for spring tension.

The black plastic piece that we removed, is 8mm by itself. (not counting the metal contact button in the center) Which means that there will still be a little room for spring tension. (like 1 or 2mm's)

Anyway, the cap is on it's way back to you. Please post back!
Jay

 

[leukoplast]

Ok, got the tailcap moments ago in the mail. I popped in the three RCR2's and screwed it on. And as I suspected, it doesn't screw on all the way, but it does screw in enough for comfort.

Thanks again Jay for the mod. Although the tailcap clicky is a lot rougher than it was before. :'( It feels like it is catching on something each time its depressed. But it works and that all I really care about. Now I just gotta wait to get home so I can test the output. All three of my batteries were at about 4.09v, and the output appears if its unchanged from when I just had two CR123's in there.

 

[jayrob]

Hmmm... Hopefully it screws down far enough to hide the threads so it looks nice. Not sure why the button would feel different...
Jay

 

[leukoplast]

When I screw it down to the point of where it would break something if I kept going, there is about a 2-3mm gap.  It's not horrible and does hide the threads, but its definitely not flush.

And you said you greased the clicky right?  Maybe the grease hardened or dried.  Cause there is a slight catch when depressing it.   Although with more use it seems to get less and less noticeable.

EDIT: Ok wow...I just pulled out my batteries and the one in the middle and the first one now has huge dents in the middle of them     Guess I went a little too far in trying to screw it down all the way.   You think the batteries are still ok to use regularly?  

With that said, if I do not over tighten the cap, there is now threads exposed. Gap is easily 4-5mm.

 

[jayrob]

Something is not adding up. You said the batteries were 26mm each. That is a total of 78mm...

I know for a fact that the host easily fits 2 X 3.6 volt UltraFires 'stock'. That is 70mm. We took out the black piece of plastic from the tail cap, and that is 8mm thick. (not counting the brass center button)??

You sure those batteries are 26mm? Or are they 26.9mm?

Anyway, I think I have a fix for you...

First check to see just how much room you have inside the pill between the bottom of your driver and the top side of the battery contact board.

If there is a little room there (you can clip your LM317 heatsink shorter to make room), then you can unscrew the pill a few turns. This will make your battery compartment longer!

All you have to do is make absolutely sure of the measurements. Because you do not want to crush anything by turning too tight like you did with the batteries. Once you know where you can safely have the pill positioned, mark it. Then take it out and wrap the threads with aluminum foil, so that you can thread it back into the position needed, and it will still be tight enough to make good contact to the host. (this is your negative contact point)

You should be able to gain some more room in the battery compartment by using this method...
Jay

 

[leukoplast]

I measured the batteries, they are exactly 26mm from my manual measurements. I don't have any fancy digital measurement devices, so it could be a tiny bit more than the naked eye can tell by looking at a mm ruler.

Also, I cannot imagine how the black insert gained me 8mm of length, it was pretty much flush with the backside of the tailcap from what I could tell when I took it out. At most there was a gain of 4 or 5mm from removing that (basically the thickness of the black thing). This is why I was so surprised you didn't remove anything else inside the tailcap. Cause when you line up the tailcap to where it would be normally if it was screwed on all the way (by holding it to the side of the host), there would be about 10mm from the end of the host body to the end of the cap (not including the switch button). And the batteries stick out probably about 5mm from the end of the host body. So with 10mm of internals in the switch, and 5mm of batteries sticking out from the host body...the measurements just didn't add up. I will take some pictures later when I get home from work to show you what I mean. But physically it was impossible unless extra tailcap internals were removed.

And thanks for the tip on how to gain some extra length. I'll probably just leave it like it is cause it's good enough for normal operation. It doesn't jiggle or anything like that, so I am fine with it. This is only a temporary host anyway, until I could find a smaller one that I could use. Cause while the construction and heatsinking is incredible, it's just so darn big!

Oh, and about the batteries. You think they are ok? Or do you think I have crushed some internal stuff in them making them unsafe for use? Cause the dents aren't absolutely massive or anything, but you can definitely feel and see them.

 

[jayrob]

I measured the black plastic piece that we took out of the tail cap, and it was exactly 8mm thick. That means you gain 8mm, because the batteries can go all the way to the metal ring now. The spring is cut short enough to allow the batteries to touch the thin rubber insulator that surrounds the spring...

But the other idea of moving the 'pill' to make more room would be an easy thing to do.

About the batteries, most likely they are fine. If there was a problem, you would already have known. When lithium batteries get damaged in this way, they will get hot. They can even start fires. But if the batteries are still holding voltage and taking a charge, then they are fine.
Jay