not so quick battery question

[tcr03]

so i see that you can use the 18650 battery on alot of flashlights that use 2 123 batteries. now the 18650 batteries are rated at 3.7 volts but 2 123 batteries would be at 6 volts. would you be losing lumens by going with the 18650 battery, or how does that work.

i have the fenix tk11R2 and am wondering if im short changing myself by using the 18650 bat instead of using two 123 batts

 

[Ragiska]

that depends entirely upon the light. if it was designed for 18650's, then you will be gaining lots of runtime at 0 brightness expense. if the light was not designed for them, but merely made to fit them, then either option is entirely possible.

look at the runtime graph for the tk11 r2 and i think you'll have your answer.

 

[kito109654]

By using the 18650 you are getting a good bit of extra run time and not losing any output. Run time on high is increased by about 80% and runtime on low is increased by about 20%.
The capacity is almost 2 watt hours larger in the 18650 vs 2xCR123. I believe the increase is more substantial on high because the 18650 handles the higher current draw more efficiently than the 123's. (lower voltage requiring less draw for same output...or something like that)
I'm still learning so I'm sure that's not the whole story but that's as far as I understand it.

Would love it if someone could add to that.

 

[HKJ]

so i see that you can use the 18650 battery on alot of flashlights that use 2 123 batteries. now the 18650 batteries are rated at 3.7 volts but 2 123 batteries would be at 6 volts. would you be losing lumens by going with the 18650 battery, or how does that work.

This depends on the led, most modern leds has low enough Vf to just about keep the brightness with 18650. But even if the light loses 20-30% brightness when the battery drains, you would not really be able to see it.