Will a 17670 run a u2 ultra?????

[skippster76]

Hi i have 2x 17670 which i run my surefire kroma mil-spec, can i use these to also run my u2 ultra, many thanks,jim.

 

[AaronM]

If it will fit in the battery tube, it'll probably work.
Alot of people use a 18650 cell in the older U2s that had removable battery tube sleeves. Or as in my case, a later model U2 with a custom bored batt tube.

 

[c0t0d0s0]

I wouldn't be so sure.

The original U2 had a boost type circuit to drive the LuxV with its 6V+ forward voltage. That particular circuit worked OK with a single li-ion cell. The U2A, on the other hand, uses a SSC P4 which has a much lower forward voltage - around 3.5V - and would need a buck circuit when powered by 2 lithium primaries, as intended. As a result, it might underdrive the emitter when using a single li-ion cell, or the levels might get messed up, or it might not work at all... who knows.

Someone with a U2A needs to try it and report the results.

 

[digitaleos]

I wouldn't be so sure.

The original U2 had a boost type circuit to drive the LuxV with its 6V+ forward voltage. That particular circuit worked OK with a single li-ion cell. The U2A, on the other hand, uses a SSC P4 which has a much lower forward voltage - around 3.5V - and would need a buck circuit when powered by 2 lithium primaries, as intended. As a result, it might underdrive the emitter when using a single li-ion cell, or the levels might get messed up, or it might not work at all... who knows.

Someone with a U2A needs to try it and report the results.

Just tried the 17670 in my U2A and all levels work.:wave:

 

[redsfairlane]

I've used one in my U2A as well and it works fine. Have not done a run time test yet though, but after several minutes all is well.

 

[cl0123]

c0t0d0s0,

Good points and thanks for the warning. I have picked up a Leef 18650 tube for the newer crop of U2 (P4) and tested it out earlier. While there were no apparent over-heat or under-drive issues, I never compared the highs and lows between the 18650 and the 2xCR123.

It's working, in my case, but he raised a good point because I am not sure if the same min and max outputs are delivered.

Wish there is a gizmo to attach a clip and a lanyard to the Leef body though.

With Aloha,

Clarence

I wouldn't be so sure.

The original U2 had a boost type circuit to drive the LuxV with its 6V+ forward voltage. That particular circuit worked OK with a single li-ion cell. The U2A, on the other hand, uses a SSC P4 which has a much lower forward voltage - around 3.5V - and would need a buck circuit when powered by 2 lithium primaries, as intended. As a result, it might underdrive the emitter when using a single li-ion cell, or the levels might get messed up, or it might not work at all... who knows.

Someone with a U2A needs to try it and report the results.

 

[skippster76]

Hi all and thanks for all the advice, will stuff a 17670 into nit when it arrives:wave:

 

[sheldonsmith]

Two newby questions...

1. How can you discern a U2 vs. U2a

2. Is there a DIY out there on this kind of upgrade (source for parts, steps).

Bumper-car-ing my way through this and any insights are appreciated.

-Sheldon

 

[PhantomPhoton]

An older U2 uses a Luxeon V emitter whereas the new-ish U2A uses a SSC P4 emitter. So after hanging around here foe awhile you can look down the business end of the light and find out visually. I'm sure there's some other way to tell themapart as well.

Lighthound.com used to sell some of the Leef-made 18650 tubes for the U2. I dont' beleive they have them anymore so you're likely out of luck for 18650s. You can purchase 18650 and 17670 cells made by AW, the most often recommended cell around here, at Lighthound as well. It is likely that Surefire has made the U2 barrel small enough that a 17670 may not fit in there. So you may have to have someone bore out the tube a bit to make one fit. So there's not really a DIY kit available afaik. If you're lucky enough to have a 17670 and U2 that fit together there's no other steps needed other than put battery into tube and put tailcap back on.

 

[:)>]

I have 2 of the U2A's and have used 18650's in them and they have retained smooth operation of all levels. I do notice that the output is less on high when using 18650's vs. 2 x CR123's