Spare KL4- Cr2 power pack?

I have a spare KL4 that needs a home. I have seen them mated with small power packs using a single cr2 battery. I thought this was interesting so I was wondering if someone could help me with some additional info. What powerpacks will work? Whats the smallest cr2 that will work? Can you get/make/modify a powerpack the same size with 123s? Which would be better? Can you get/make/modify a two stage switch for it? Lots of questions I know, but any comments are appreciated. I have a thing for small really bright flashlights.
Thanks,

Travis

The L4 is a heavy draw head. To power the Lux V, you need enough power to drive a Vf of approx. 7.5 V at 0.7 A plus efficiency losses ( 7.5V x 0.7A x 1.1) = 5.8 watts.

In a single CR2, that is 5.8 watts / 2.5 V = 2.3 A.

I have a CR2 side x side project in the works, so I have some understanding of CR2 limits. If your L4 turns on, it will be for only a few minutes. (maybe 5 max). I would use only rayovac or streamlight cells at that kind of current draw. Even then, you are risking cell damage due to heat.

I admit my ignorance in these matters. I thought that the cr2 was similar to the 123a in regards to voltage. A kl4 can be powered by a single cell 123 so I thought it could be powered by a single cr2?

Hi - we are all learning - believe me. The CR2 is very similar to a 123 in terms of voltage, but it has considerably less capacity for current delivery. Under load, the voltage in both cells will sag from the nominal 3 V to approx 2.5V (see the posts by silverfox in the battery / electronics section comparing 123 cells).

NiMH and NiCd cells can delivery high currents, but Li primary cells like 123 and CR2 are really ideal for 1 amps and less. At 2 + amps, they will drain very fast, that is the challenge.

on a single 123 it's not as bright as a with 2 123's so I would think with a CR2 it would really be dim. Now a RCR2, on the other hand - that might work since the KL4 works under full reg for at least 20 minutes on a RCR123 or R123

I appreciate the input. I guess the cr2 is out, atleast for now Any other thoughts for a interesting combo with a KL4? I already have a KL4+aleph1x123+mce2s which I think is great.
Thanks everyone for you help

Travis

I believe the Sandwiche shop sells(or used to) a CR2 pack for the aleph series. A RCR2 would give good out put but for only 10-15 minutes. A R123 is the way to go.

If you're not interested in a rechargeable CR2, I don't think anyone makes a 2xCR2 - but that's no real benefit over a single RCR123 or R123 which will still be smaller.

since you already have a TW4 (KL4 running off single R123) I'd consider a 17670 Li-Ion cell - same size as 2x123 but rechargeable. Nice, bright, and freeeeeeeeeeeeeeee!

Either that or sink $20 into a R123 or RCR123 setup since it will be noticibly brighter than your current setup with non rechargeable 123's

It looked like you can get an Aleph 2xcr2 body (also called a 123ax1.5) but i'm not sure that it has much of an advantage over a normal 2x123. I may go the rechargeable route.

You can use an Aleph 1.5 x CR123 pack (PILA 150S version) for 2 x CR2 ...
... or the Aleph 1xCR2 pack for 1xCR2, but this combo, as the others said, shouldn't be a home run.
bernie

I run a KL4 on an RCR2 in an Aleph CR2 body with a flat 2-stage tail switch. I don't notice any difference in output as compared to using an R123 or Pila 168S. Maybe a side by side comparo would show me the difference, but I don't see it. Certainly would be a diminished runtime, but I dont use this thing for extended periods and regularly switch to a newly-charged battery. It is bright and small, thats for sure.








best regards

Where did you get your rcr2? That is exactly what I am interested in.
Thanks

What resistance for the two stage switch do you recomend?

Click here for rechargable CR2 batteries. PM the seller, CPF member "AW", to see if he has a "nano" charger for them. This charger costs only a few bucks ($8?). The charger is made for a R123 battery, so you have to insert 5 pennies along with the RCR2 battery so the penny/RCR2 combo is the same length as a R123. Works just fine, and this is what everyone uses.

There are probably other vendors out there too. Maybe someone can chime in.

As for resistance on the Aleph 2-stage switch, I prefer really low light on the low stage (good for movie theaters, checking the kids at night, etc.), which is (I think) a higher number resistor. Can't give you an exact number on mine as I don't remember. I'd say get something in the middle range of the resistors that are offered. If you don't like it, you can order another resistor cheap and install it yourself. Check out the McGizmo forum for info on this, and PM me if I can help.

Might also consider a KL4 on a R123 battery. Not much bigger, still small, and better runtime on high.

best regards

KL4 w/mclux CR2 pack and Mce2s tail in Z52 surefire tail is one of my favorite combo's

mostly use low beam which last for several hours. burntime on high is pretty short.

can only use CR2 li-ion. very useful combo when combined with Xbin KL4.

Thanks everyone for their help. I am going with the cr2 body/mce2s switch using a rcr2. I also ordered some r123 for my tw4. When I get everything in and put together I would be happy to do some testing (informal). Size comparisons, run time comparisons, etc.
Thanks,

Travis