which batteries for which light?

[basballny2]

hey guys relatively new to rechargeable batteries but i just bought a pila charger, 4 rcr123 batteries and 2 18650 (2900 mah) (all AW) and 2 spacers. the question is, which of my lights can i use the rcr123's in. so far i have:
1. fenix ta20
2. fenix tk21
3. klarus nt20
thanks in advance!

 

[StarHalo]

Please thoroughly review safety and handling procedures for Li-ion cells before attempting to use them, they can explode if mishandled. Get a multimeter and head over to Battery University.

 

[basballny2]

thanks ive been reading up on them and bought the protected version on both which from what ive read is safer. im fairly new to all this and still trying to learn. for now however, my surefires are dead in my lights and i need to put these in so i was wondering which lights can handle which batteries due to the different voltages. im pretty sure the tk21 can take both the rcr123 and 18650, the klarus can take rcr123 but not the 18650 due to the tube size and the ta20 can only take 18650 and NOT rcr123. is that correct or am i all messed up haha.

 

[yellow]

and dont put too much unnecesary fear into using protected Li-Ion cells,
coming from overly anxious armchair heroes
:rolleyes:

PS: if I have the choice, I always choose the 18650 over 2*CR123.
--> More power, less "loose" parts, same sized light (... depending)

 

[basballny2]

noone knows if i can use rcr123's in my klarus nt20?

 

[BobBarker]

So... Simple answer is if the nt20's tube will fit the larger diameter of the 18650 than yes, it's safe to use. The single 18650 cells (depending on chemistry) peak at 4.2v and usually settle in to an average of about 3.5-3.7v per cell during use (this applies to most every li-ion cell (before the protection circuit). With the RCR123 they sometimes have a voltage downconverter built into them to get the 3v during use. I digress....

So easy to remember way...
1 cell is safer (less likely to damage the circuitry) than two, as long as it doesn't go below the cells minimum voltage(2.5v for the Panasonic NCR18650A cells only, everybody else is about 2.75v.)

So in your case 1-18650 cell (peak) 4.2v Or 2-RCR123 cells (peak) 8.4v
Per klarus's documentation the nt20 is rated for 3-8.4v.

The chemistry is less important in the 18650 cells (for the current drawn) than the RCR123s... Some of these lights have a nasty habit of trying to pull 2 1/2-3 amps (for single cell lights) from a battery only rated for .7-.9 amps.