Surefire U2 will not run on rechargeables?

I recently purchased a new Surefire U2 serial# A07887 and was disappointed to find it will not power up on either protected or unprotected Li-ion's 16850. The use of rechargeables was one of the main reasons I bought this light. Anyone else have this issue??

:thinking: your cells may be too short? Try completing the circuit with a piece of wire and see if it works.

You most likely need to stretch the spring on the head of the flashlight. From the factory it is long enough to contact the smaller button top of a regular CR123A but not the fatter head of a rechargable lithium ion cell.

Thanks for the suggestion. I tried it but it did not work.

Measure the length of 2x123's and compare that to the length of your rechargeables (don't short your batteries while measuring - and don't ask how I know ). That should give us a better idea of whether length is an issue (on how much you potentially need to make up for.

What's the size? Whose rechargeables are you using? Where'd you get them, I mean.

I have to use one of the rare earth magnets on top of my 18650s when I put them in my U2. You may try one of those.

Huh?
Has something changed here? I can just pop in a PILA168A or 168S and it works without any modification ... ????
bernie

TheSteve said:

You most likely need to stretch the spring on the head of the flashlight. From the factory it is long enough to contact the smaller button top of a regular CR123A but not the fatter head of a rechargable lithium ion cell.

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I tried adjusting the spring in the tailcap which did not work, then I saw your post about the spring in the head and I realized that had to be it. And now it works!!!
HUGE :thanks:!!!!

Thanks everyone for your help!

I must ask again, what cells are you using? Just for the record (ie. so I can avoid them )

did you use the little magnet nipple? if you're using the 18650, you will need to attach one of the little magnets to the positive end of the light (which makes contact with the head) so it will work. it won't make contact with the head if you don't nipple-ize your battery =)

The cell was not the problem. The spring contact inside the Surefire head was recessed and not allowing the battery to make a connection. The CR123A primaries worked fine because they were able to make contact due to the button top, but the flat top of the Li-ion was not. A little stretch of the spring was all it took.

Grubbster said:

I have to use one of the rare earth magnets on top of my 18650s when I put them in my U2. You may try one of those.

Click to expand...

Same here. The issue is the shoulder of the 18650 cell (positive terminal end) prevents the small + spring from contacting the battery. Stretching the lower spring is ineffective and the upper spring has very little substance to it. So I adopted the super-mini-magnet button top prosthesis and it works perfectly. I was stumped because 17670 cells (Pila 168 S) worked fine and 18650s (Pila 168 A) seemed an ideal fit as well but would not make contact. The tiny magnet saves the day. I get superior runtime and full brightness (all 6 levels) with my LG 2400mAh cell compared to primaries. Seems I manage to convert every Surefire I own into LiIon rechargeable platforms one way or another, even the challenging M6.

Lunarmodule said:

Same here. The issue is the shoulder of the 18650 cell (positive terminal end) prevents the small + spring from contacting the battery. Stretching the lower spring is ineffective and the upper spring has very little substance to it. So I adopted the super-mini-magnet button top prosthesis and it works perfectly. I was stumped because 17670 cells (Pila 168 S) worked fine and 18650s (Pila 168 A) seemed an ideal fit as well but would not make contact. The tiny magnet saves the day. I get superior runtime and full brightness (all 6 levels) with my LG 2400mAh cell compared to primaries. Seems I manage to convert every Surefire I own into LiIon rechargeable platforms one way or another, even the challenging M6.

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Just curious as to what other Surefires you have converted to Li-ions? Thanks.

Flashlightreviews.com has this going to 50% brightness at 1hr on the regular batteries at setting 1. With a 2400mAh 18650, around how much longer will it run on setting 1 to 50%? If Xmas dough comes in, a U2 with 18650s sounds like quite the setup.

chanamasala said:

Flashlightreviews.com has this going to 50% brightness at 1hr on the regular batteries at setting 1. With a 2400mAh 18650, around how much longer will it run on setting 1 to 50%? If Xmas dough comes in, a U2 with 18650s sounds like quite the setup.

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According to this thread, new U2s are coming with a glued plastic insert that prevents an 18650 from fitting. Some folks have managed to remove it easily while others have had trouble getting it out.
http://candlepowerforums.com/vb/showthread.php?t=99132

I was about to order a U2 until I saw this and decided to wait. It's too expensive a flashlight to have a warranty claim denied because I removed the insert and the 18650 use was very important to me.

Emillion is running a sale that's about to end on a multiple level Lux V called the QuickSilver V in the dealer forum for $60 shipped. I just ordered one. I've got the Lux 3 version from Wai On, a 3.5W Lux III called the VB-16 and like it a lot. The QS V is about as close as I'm going to get to a U2 unless the 18650 "issue" gets "resolved".

From what I remember, run time of a U2 on an 18650 was about 1.5 hours with about 10% less output than when run on 2 x CR123A.

Mike

https://www.candlepowerforums.com/threads/99132&page=2

There you find my way to take the insert off

Yeah. My 18650 just arrived. Had to put a small metal piece between the battery and the head spring. Works beautifully!!! Noticed some slight diminished output, but hardly noticeable unless you are looking for it. Don't know about the runtime yet though.