Ok guys. I got the fenix E35 flashlight free from fenix outfitters. Since I do not have any CR123 batteries and want to make use of this flashlight, Im in need of 2 things.
Im a total newb on this battery config and need some inputs from you guys.
Thanks 
Im just adding I am not comfortable in running 18650 cells and would prefer safer cr123 batteries. So please dont tell me the e35 can run those
CR123 Batteries are primary cells, they are not rechargeable. There are rechargeables called "RCR123", but they are not very common, I believe.
There are also rechargeable LiIon 16340 cells, but they are 3.7 V (basically like a small 18650).
You mean there are not many models of those on the market??
EDIT: Damn $10 for one rechargeable
https://www.foursevens.com/product_info.php?products_id=201
Hmm... please be careful, there seeems to be confusion about the correct nomenclature.
The battery you linked has 4.2V when fully charged, meaning it is LiIon chemistry (nominal 3.7 V) like the regular 18650s. Therefore I would call that battery a 16340 cell and not RCR123A, because it is not a direct replacement for 3V CR123A cells. I suppose you would fry your light with two of those cells.
There seems to be a lot of confusion about 123 types.
My AW 123 are marked as ICR123, they are 3.7V.
Another brand called DIGITAL I have are marked as LCR123 and CR-123 and are 3.0V.
Both are rechargeable as marked and have been used/charged many times, both are also marked Li-Ion
Both are same size.
I would venture to say that running a single 18650 is just as safe as running 2 cr123 primaries in series. If the 18650 has protection and is a high quality cell, there isn't much that can go wrong. There are three things that can go wrong with an 18650 - over-charge, over-discharge, short-circuit - and the protection circuit should prevent all three from happening.
As for 3.7-4.2v RCR123, that is actually the least safe option you could go with. RCR123 like the ones that you linked to are Lithium Cobalt Oxide (LiCoO2) cells just like 18650. At 4.2 max volts, running two in series will probably fry the E35. Also, RCR123 tend to be not as consistent from cell to cell as a good 18650 which makes using multiple in series not as safe.
There are 3.0-3.3v rechargeable 123 cells such as these: link. They use the more stable, less energy dense Lithium Iron Phospate (LiFePO4) chemistry. They are safer than LiCoO2 cells and they are harder to find and require a different charger (or a hobby charger). Keep in mind that LiFePO4 cells can come off the charger at 3.5-3.6 volts. Running a pair in series could potentially fry the E35. Not likely, but it's possible.
Personally I would say a 18650 is much safer than 2 CR123s. I have never seen or heard of a good quality 18650 exploding. (Protected or not) CR123s, however...
My protected Ultrafire BRC goes down to 2.5V, not good!!
I shouldn’t have been so tight when I bought 18650’s ha ha.
I think they are mostly a rip off price though, especially the better name more expensive ones.
So the general consensus would be to use 18650 cells?? They are safer when used as single batteries as opposed to RCR123 x 2?? Hum…
That fits with everything I’ve been reading. A single cell is, as a general rule, going to pose less risk than multiple ones. Given that the E35 is regulated and offers fairly good protection I don’t think you’re taking any great risk.
Fasttech sells Nitecore 16340’s and cr123’s at a great price
http://www.fasttech.com/search?Nitecore
Hi guys. Im back after a HD crash. One of my worst fears in life occured and I lost so many important stuffs 
I was reading the fenix e35 manual which arrived FREE courtesy of some draw I won and it said “!” besides 18650 cells…
Link to the manual is here.
http://www.fenixtactical.com/manuals/fenix-e35-user-manual.pdf
This flashlight is absolutely gorgeous. Pocket rocket and seems way brighter than 225 lumens claim. Heck, to my eyes it even matches 400-500 lumens flashlights. The spill is generous and the build real quality. Maybe I’ll post some beamshots later but right now I’m stuck at battery choices…
Help please! So is 18650 still the way to go? The 5 lumens at 155 hours is absolutely awesome. Very impressive.
Yes, absolutely.
But measure the interior tube dimensions first and make sure to buy batteries that fit. I have a feeling that protected Sanyo 2600 might not fit. Pansonic 3100 and under would probably all fit. But I'm just guessing.