hey guys need some info on these 2 battery's 18650 protected vs 2 of the >>>cr123
and is a single 18650 protected cell that's rechargeable the same as 2 cr123 cells ???
im making a thrower flashlight using a L2 host using a EZ900 led and a 1.5A driver witch would be better for run time/power ect......
18650 max voltage is 4.2v. capacity can be up to 3100mAh.
2 x cr123 maximum voltage is 6v. Can be 3000mAh I think.
Depends on the driver voltage range most are 4.2v therefore the 18650 would be better for everything. as the Cr123 voltage would be wasted.
If the drive voltage is up to 6 volts then the CR123 would be better, Runtimes for this I'm not to sure.
I would stick with the 18650.
the driver is a 8x7135 2.8A modded to be 1.5A
Err, no. It’s either 6V / 1500 mAh or 3V / 3000 mAh. In both cases, amount of ENERGY for single CR123 is 4.5 Wh, and for single 18650 it’s 11 Wh… which makes it being able to store more energy than pair of CR123’s (and at same time it’s rechargeable).
What's the voltage? Is from 0.7 to 4.2v or 4.5 to 8.4v or something like that?
sounds good now a source for 18650 protected/rechargeable
Was not think.
Input Voltage i think is 2.8-6V
Go with the 1860 as they are better you can use cr123 as backup
He can't, actually. 7135-based drivers are linear (meaning they output voltage differential between batteries and LED as heat), running a 7135 driver on 2x 123's would fry it, and 1x 123 wouldn't even start it up.
2xcr123 would work fine, particularly with a higher Vf LED like a XR-E. 2 RCR123(3.7v) would not be OK.
so u guys would go with a 18650 battery ?
Unless you really really want primaries instead of a rechargeable, the 18650 would be my choice. It's much cheaper to operate in the long run as you only need to invest in one battery (two is handy) and a charger.
It would work, but roughly a third of your battery power would be wasted as heat as the 7135s bleed off the excess voltage. 
As others have suggested, a single-cell Li-ion setup would be best.
True, but he'd be getting full output for almost the entire run, which can't be said for a single 18650.
I'd go with a Sanyo 2600 cell for its lower IR (holds voltage higher than the Panasonic 2900/3100 cells) and I'd probably leave another chip on there for 1.7A.
I have several flashlights (S-mini, Pelican, a few others) that can run on 18650 batteries or 2 x Cr123's. I don't notice any difference in brightness or runtimes, to my eyes it is 6 of one or 1/2 dozen of the others. I like the fact that if I can't recharge, I have a decent supply of CR123's that will still work.
I have two p60 drop ins that can be used with two cr123a's or a single 18650. One of them is the solarforce 3 mode XML. When using cr123a's I get 2+ amps on at the tailcap on high. With the 18650's I only get about 1.4 - 1.6 amps.
A regular cr123 battery is around 1400 MAH in capacity and a decent 18650 is 2600 MAH. If you use two cr123s in series you’ll get only 6v and 1400 MAH. You’ll stress the driver and maybe get a higher output for a short period of time but then your cells will get warm and limit the current they put out. And that 2v advantage of the primaries setup will be wasted in the driver. AMC drivers are already efficient drivers for lithium ion voltages so the output current will stay the same for a long time. But 2x123 s should be depleted in no longer than the half time of your 18650s and they would run hotter as well. Using buck drivers and low voltage emitters is the ultimate solution for me. I use them in extended l2 bodies with two 18650s for longer runtime, remove the extender and put just two cr123s in case I’m out of power.
The AMC7135s are not good doing a good job when the input voltage is far from the Vf of the LED. The efficiency is about 60%, which is very inefficient. A CR123A battery has 3.3v when it's fresh. So you'll have 6.6v with 2 in series. A 18650 battery will drop that 4.15v 4.18v quickly under 4v and be very close to the Vf of the LED, thus the efficiency will be extremely good.
Once I'm past the point of matching the voltage range to the drop in... my eyes glaze over. I don't know how anyone can keep it all straight. The consensus, in this and other threads seems to be that the 18650s are the way to go instead of cr123s. But because of all the complexity and "danger" regarding the charging, all the math and engineering I seemingly have to learn, and those pictures of intricate charging systems elsewhere on this forum, etc, in the end, I just keep using cr123 primaries because that seems like the simplest solution despite the continuing cost or battery replacement.
I'll never get my flashlight black belt at this rate. 