Request for U2 runtime graph with Pila cell

Could someone please make a U2 runtime graph on level 6 (max.) using a Pila 168A or Pila 168S cell, preferably compared to a graph using 2xCR123A. I think we need to establish just how far out of regulation it is on level 6 when running on a Li-Ion cell. Thanks.

Jan

Yes we do indeed. Anybody with a light meter able to help us out? I have only a basic DMM so I can only take instantaneous measurements of the current.

I am experimenting with my U2 and a salvaged unprotected 18650 cell (same dimensions as the 168A). The bad news is that I seem to have lost level 6 completely - I get up to 5 max, then the last turn of the dial to go to 6 produces no improvement at all whereas with CR123s, the improvement is immediate and very dramatic.

However I'm not sure if this is due to the age of my cells and their inability to withstand the current drain. These cells should actually be FAR FAR beyond their serviceable lives (they've had 3X the mileage they're rated for put on them, they've been discharged to 2.5V and left to sit for three years, and they're 8 years old..).

I will follow up on my observations with newer 1800mAH cells when the owner of the pack gives me permission to rip it apart. /ubbthreads/images/graemlins/huh.gif /ubbthreads/images/graemlins/grin.gif

Rechargeables are cool but so is Level 6 /ubbthreads/images/graemlins/smile.gif

Got hold of the new 1800mAH Panasonic CGR18650 cells, and I'm not impressed. The U2 does not hold level 6 for very long - when the cells drop to around 3.7V or lower (their nominal voltage) you only get level 5.

After letting the cells rest a little, level 6 comes back. A current check when the cells are fresh indicates 1.35A, which is not even a 1C discharge.

We need someone with a logging DMM or photocell to keep an eye on this. The U2 apparently doesn't do well with rechargeable cells. Lithium primaries may be a better bet because they can withstand the 1.4A drain for longer (40 minutes - my guess).

I'd be very interested in seeing the Photon King release an official rechargeable kit for the U2. If it can keep up with level 6, well....looks like they're gonna make me spend money again /ubbthreads/images/graemlins/grin.gif

I'm pretty sure it's not the amp draw but the lower voltage of the rechargeable cell that's causing level 6 to tank. For the record, both of my pila 168s cells stay above level 5 for the duration of the discharge.

Above level 5...so you mean yours stay in 6 until they're depleted? Or do you mean that they hold at least level 5 all the way till the end?

I've been running U2 with JSB 3V R123 with no problems and getting all 6 levels.

runtime is not very long and it's a pita recharging 2 cells in a single cell cradle. but it works GREAT!

We now have confirmed data from at least two independent testers (Thank you: KevinL and Ray_Of_Light /ubbthreads/images/graemlins/bowdown.gif) that it won't run in regulation on level 6 for the majority af the battery runtime on one Li-Ion cell. That sucks IMHO.

It seems like the L5 is a much better performer on Li-Ion cells then. IIRC the dc/dc-converter in that light is the same as in the L4, which runs in regulation just fine on one Li-Ion cell (Pila 168S/1400mAh) for at least 50 min.

The fact that the U2 wont run level 6 for very long, would however be justified, if it is significantly brighter than an L5, and if there exists a level that equals the output of an L5 (level 5 perhaps?), that would run the U2 in regulation for at least 50 min (still talking Li-Ion of course).

Jan

jan, my U2 runs fine on JSB 2x 3V li-ion. just that charging is a pita.

I'm very happy with output of my U2 (Xbin?). low levels are proving to be very useful as a tent light. that duty is usually covered by ARC AAA. but U2 covered all light requirements on my boy scout campout last weekend.

only drawback so far is U2 is a little big.

Cy, yes I know. Two Li-Ion cells would run it in reg. but not for very long, as you also mentioned. In my book, good Li-Ion performance is at least the same brightness as an L4 or L5, for at least as long time (50 min.). Well I don't know, maybe it's to much to expect from a light with multiple levels which probably is designed primarily for use with CR123A cells.

Jan

until something better somes along. seems JSB's 2x 3V li-ion are the only rechargeable option that works at all levels with U2.

not a runtime guy. hats off to the runtime guru's /ubbthreads/images/graemlins/bowdown.gif

I'm thinking aprox. 15-20 min of bright w/2x JSB 3V on U2.

edit: circuit breaker kicks in at aprox. 5 minute due to batt overheating

Hello Jan,

I am just finishing up a test comparing SureFire 123's, the Pila 168s, and the Pila 168a. I am running the test at 1.5 amps. You should be able to draw some conclusions about U2 use from the comparison.

Look for it in the battery section. I think I will call it "U2 Battery Comparison."

Tom

Hello Jan,

The U2 Battery Comparison is posted.

Tom

Tom,

Interesting, thanks a lot for the graphs ./ubbthreads/images/graemlins/bowdown.gif So if the U2 needs more than say 3.7 volt to run in regulation on level 6, it certainly won't stay there for long on any Pila, acording to your graphs. It confirms what others have noted.

If Surefire intended the U2 to run on rechargeables, it's going to be interesting to see what kind of technology they'd implement.

Jan

Hello Jan,

I found the testing very interesting.

Do you happen to know what the minimum voltage for level 6 is? Hopefully it is closer to 3.5 volts.

Tom

[ QUOTE ]
SilverFox said:
Hello Jan,

I found the testing very interesting.

Do you happen to know what the minimum voltage for level 6 is? Hopefully it is closer to 3.5 volts.

Tom

[/ QUOTE ]

Theoretically, minimum voltage for full-on level 6 should vary with Vf of the led. I'd like to see some data to back this up though.

I "swear" my U2 is getting brighter the more I run it.

Someone send me a U-2 and a box of batteries and I'll do some runtime plots! /ubbthreads/images/graemlins/grin.gif /ubbthreads/images/graemlins/crackup.gif /ubbthreads/images/graemlins/santa.gif

We have two possible causes for this **Hmmh** behaviour

Inefficient converter design or high Vf LEDs

I think it would be a damm shame if going forward with technology Surefire would have stepped back efficiencywise designing a circuit which while having 6 dimmable settings would do as badly on the high level - compared to the L4/L5 which weren´t as great efficiency-wise but at least worked fine with either 1 x LiIon or 3 x NiMh cells including low-discharge protection for LiIons.

Now one would have expected somehow that SF would be keeping that performance intact AND raising the bar in adding the dimmer settings - now I still **HOPE** that the batch of LEDs used was on the very high Vf side causing this problems and using a lower Vf LED will fix things.

So far I´m happy that I didn´t jumped on the U2 waggon yet

Klaus

sure wish there was a easy way to open up U2 to measure vf. I have noticed that lower vf lux's seems to maintain white tint at low currents. VS going greenie.

this based off of using lots of sammies w/two stage switch, li-ion & CR123. Hbins consistantly had better tint on low.

Klaus.. you've made some really good points there. My working assumption with the U2 was that 'it's done when its done (properly)', and thus would be better than the L4/L5.

I'm actually looking at an L5 right now (shocking ain't it? /ubbthreads/images/graemlins/faint.gif), it could be bored out to accomodate the 18650s I like.

Basically, I regard the situation as a compromise, with rechargeables you take a performance hit but you do get the awesomely long runtimes - at 800mA, I'm looking at easily 2 hours on 1600mAH. Of course, not having level 6 is really no fun. 6 IS a heck of a lot brighter. I'd say it's the difference between 70 and 100 lumens on mine.

For those who need level 6, I guess, it's back to primary cells again. I just wish I didn't have to make this compromise on what, in my eyes, is THE light that refuses to compromise (or should refuse to /ubbthreads/images/graemlins/icon23.gif)

The reason I won't be trading down to a L5, much as I love the body style (the C2 was a big hit with me) and the ability to run full power on lithium ion is that I still value the multiple levels and the bezel down clip.

It would be great if we could get a few words from the Photon King himself on the subject, even if it is "It looks like you'll have to live with it". Do you think it would be wise to bring this up with him?

I don't see a huge problem here, nor do I think the U2's efficiency has plunged.

In a side by side runtime test between my u2 and l4, they both ran within a minuite or two of each other before dropping out of regulation. This test was run with 168s cells.

Everyone talks about "no level 6". Well you do have a level 6, just not a wide open one. I notice a big difference in 5 and 6 on pila cells and primary cells.

And, I'll repeat it again that I swear mine is brighter after running the light for a day or so. Please see the thread about luxeons and vf dropping as they age.

Also, for those concerned about efficiency please be sure to remember that not only is the u2 brighter (even on a pila cell) than the l4 but it STILL has to run a continual check on the hall effect circuitry to see if you have changed the level.