U2 on 2x150s ????

Ok i have 2 pila 150s' for my sf c3 and now that i have my u2 i was wondering if i could put an extender on my u2 and run it off of the 2 cells. Sence the led is regulated would i be right in thinking that the current going into it is limited? so that i wouldnt be overdrinivg it with the 2 larger cells? would this work ?? has anyone tried it? this would increase runtime alot right? give me your guys' opinions

Depends if it has a buck circuit too. Other 5watt SF's only have the boost, so it might be an expensive experiment.

It seems that many have jumped onto the U2 bandwagon. If the U2 is a two cell light, the odds are strong that it is running a boost converter. If so, going with two li-ion cells will likely create a situation wherein the Vin exceeds the Vf of the luxeon. In short, it wouldn't be a good idea.

Chop has it right. On my U2s, when battery voltage exceeds about 7 volts, the light goes into direct drive and you also lose the ability to dial down the output with the selector ring. Your U2 might run for a while, very brightly, on two Li-ion cells, but you will lose LED lifetime and some of the functionality of the light at a minimum, and might permanently damage it at worse.

First and foremost,

The cell FITMENT issue. The C3 is a three 123 cell light, the U2 a two 123 cell light with room to spare, in terms of cell diameter. Two Pila 150S cells are the length of three 123 cells, way too long to fit the U2's battery tube. Although the tail section is compatible with the SF A19 and Lighthound MC123 cell extenders and in theory you could add another 123 cell length to the U2 the bore diameter of the U2's tail makes for a very tight squeeze for Pila S cells, which would require a little modding with a Dremel or peeled Pila for a nice fit.

The weird proprietary inverse-to-comparative-model (inside out) threading of the head is still a mystery to me, not sure why SF went this route but it seems the U2 head would have made an awesome swappable piece to use on C/Z/P series lights if they shared the same thread size, as they do in the U2's tail section.

Its really a moot point anyway since the nicest feature of the U2 besides the multiple levels IMHO is the ability to digest a fat 18650 (I use LG 2400mAh cells for superior runtime) or Pila 168A cell. The U2 is the only Surefire light that can accomidate that cell in stock configuration, some folk here go to a bit of trouble boring out the bodies of C/Z/P series lights to make 18650s fit.

Its a blessing that the light works perfectly on all 6 levels with this single LiIon cell for me, with a small hitch: a small round magnet is required for the (+) terminal of the battery for proper contact. Some folks bend the short spring from the head outwards a bit accomplishing the same task.

As correctly stated above, two Pilas in series would cause an overvoltage condition and harm the electronics and emitter, likewise 2x R123 3.7V rechargeables are on the NO-GO list as well. Lux Vs dont have a stellar life rating (500 hours or so at spec IIRC) and overdriving it is just bad news: why risk losing the multi-level adjustability and permanent damage?

OK, so I think I've enough.


I hope this helps somewhat.....

wasBlinded said:

Chop has it right. On my U2s, when battery voltage exceeds about 7 volts, the light goes into direct drive and you also lose the ability to dial down the output with the selector ring. Your U2 might run for a while, very brightly, on two Li-ion cells, but you will lose LED lifetime and some of the functionality of the light at a minimum, and might permanently damage it at worse.

Click to expand...

Same here. You run a wee bit brighter but the result is you loose the ability to dial the levels correctly. My initial attempts lastyear were with an A19 in an effort to gain runtime but two RCR123a do the same thing.