2 18650's in 2C Mag with no spring = It actually worked great

bigchelis

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Hi all,

Today I was trying to fit 2 18650's in my 2C ROP build. I already ordered the fivemega deep/wide tail cap, but figured I would try this differently....

If you remove the stock spring and put a PVC pipe from hardware store (cell holder) then put tail back on = it works perfectly. No rattle and everything fits super snug.

What are the drawbacks of using it this way????

If there are potential issues I can put the stock spring back in, but stick it all the way down and super short. It will be a super tight fit, but I can make it happen.

Any thoughts?

PB060333.jpg



Notice how much the 2 18650's stick out, yet the stock tail cap fits perfectly snug.
PB060335.jpg


PB060336.jpg
 
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ElectronGuru

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Wow, so the dimples added to the latest cells, allow it to make complete contact with the flat 'wall' found at the bottom of the tailcap. Genius!

The only question is what would you be giving up? Off the top of the head, two things a spring does are 1) absorb shot/movement and 2) adapt to different length cells. So to the extent these aren't needed, rock on.
 

bigchelis

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Wow, so the dimples added to the latest cells, allow it to make complete contact with the flat 'wall' found at the bottom of the tailcap. Genius!

The only question is what would you be giving up? Off the top of the head, two things a spring does are 1) absorb shot/movement and 2) adapt to different length cells. So to the extent these aren't needed, rock on.

The nipples at the rear of the cells are left over from when I recycled them from a former HP Laptop.:whistle:


I just tried AW 17670 cells and it wont work. I will put nipples at the rear of the tail cap to see if I can get it going with the ROP L bulb of course. You are correct without those nipples it wont work.

back to work...lovecpf
 

Justin Case

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The dimples are no doubt from the little spot welds that held the nickel straps in place, connecting the 18650s in a laptop battery pack.
 

bouncer

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Big Chelis,


Which bulb are you using in your ROP ? I' ve be thinking about building the same basic setup using the new AW 18650 2600 mah with the dimples and I was wondering if the 3854 H will instaflash. I have heard most ROP conversions with IMR 26500 tend to flash the HI lamp. I'm looking to build a decent ROP with some runtime. I've been rereading all of the threads and charts and I'm still trying to decide which is the better way to go 18650 vs IMR 26500 ?
 
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bigchelis

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Big Chelis,


Which bulb are you using in your ROP ? I' ve be thinking about building the same basic setup using the new AW 18650 2600 mah with the dimples and I was wondering if the 3854 H will instaflash. I have heard most ROP conversions with IMR 26500 tend to flash the HI lamp. I'm looking to build a decent ROP with some runtime. I've been rerading all of the threads and charts and I'm still trying to decide which is the better way to go 18650 vs IMR 26500 ?

I been using the 3854 Low for this threads purposes, but I have been using the 3854 H with 2 IMR C cells. They measure 4.12v each and have been working well. The 18650 Route is just for flexibility.


bigC
 

Tony Hanna

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If you need a little extra space you can ditch the snap ring, loosen the set screw and move the switch forward a little (you'll also need to file a little on the switch housing to get the rubber cover to fit with the switch moved forward). I've got room for 2x protected 18650s and a small spring with the stock tailcap that way.
 

ElectronGuru

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If you can get your charger to stop at 4.1v, the 26500 + 3854 is less likely I poof. This is a good confguraton if you want peak output. My chagers stop at 4.2, so I prefer 3853 with same cells.

The 26500's are petty amazing, so the first quuetion is which battery mod makes more sense, since neither fits without some work.
 

bouncer

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That's what I thought the 18650 tail cap mod seems easier to me I was just wondering if the protected 18650 had enough sag to reliably run the 3854H with out flashing. I would probably use the low more frequently but since I have to buy both in a pack I want to be able to use both. I got enough unused junk around the house now !!! LOL
 

kramer5150

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If you need a little extra space you can ditch the snap ring, loosen the set screw and move the switch forward a little (you'll also need to file a little on the switch housing to get the rubber cover to fit with the switch moved forward). I've got room for 2x protected 18650s and a small spring with the stock tailcap that way.

:twothumbs... great tip, thanks
 

Mjolnir

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Before I got IMR 26650s I was running the 3854H off of fully charged (but protected) 18650s. It was completely impractical, since I had to press the switch 5 times before it would turn on (because of the protection circuit). The protection circuit might have been preventing flashing. I also ran it off of 2 unprotected cells from a laptop battery, but they probably sagged more since they were older.
 

bouncer

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Which 18650's were you using ? AW's new 2600 mah have a 5.2 amp max discharge and will fire a WA1185 in one click. Those are the ones I would be using.
 

Mjolnir

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I was using trustfires, which I know have a lower limit. The AW cells should be safe, but I'm not completely sure since the protection circuit on my cells probably reduced the risk of flashing the bulb.
Usually the only issue with the 3854H bulb is with IMR cells and larger lithium ion cells (like D cells). I don't think that 18650s will flash the bulb. I can run my 3854H bulb with 2 4000 Mah IMR 26650s at 4.1 volts each (I haven't gone higher than that because I don't want to risk destroying the bulb). These are fairly large cells and sag a lot less than 18650s, so you should be fine.
 

bouncer

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I just bought a ROP low setup for 18650 at the marketplace.WOOOHOO !!!
 
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