I’m getting an SK68 with a red CREE Q5 LED - it will take 14500 or AA. I know the 14500 will drive it brighter, but in my case I am interested in runtime. Does the 14500 run low quicker because it is able to provide more power?
In my case I have available to use:
- Xtar 14500 rated at 800mAh
I guess it would all depend on on the drivers settings.
imo any sipik sk68 clones I tried always run longer with nimh than 14500
That’s all the info you need… Measure your tailcap current with both cells, then calculate your runtime based on that value vs. the rated cell’s capacity.
Ouchyfoot is right driver settings play a big role. The two batteries you listed have 800mAh at 3.7 volts and 2500 mAh at 1.2 volts. So take those and get joules right? (3.6 coulombs per mAh times voltage)
Xtar 10656 joules
Tenergy 10800 joules
They have roughly the same energy inside them…
Here is why I asked. I bought this Xtar WK41 recently and was surprised to see the difference in runtime between AA and the 14500. It stood out to me as this is my first 14500 light and I thought it was going to be longer runtime on 14500.
If we focus on the High mode (where I will use it most) it says the AA will run 5 hours, and on the 14500 it will only run 1.9 hours. Big difference if we’re assuming similar capacity.
High on Ni-MH 60
High on Li-Ion 150
But your getting twice the lumen with the 14500, so the better way to look at it is the 14500 doubles your available output not halves your runtime…
The other issue is even on cheap $.25 ea alkalines (Dollar tree sunbeam brand), for 300 cycles you are spending about $75 on batteries. Two 14500’s (good ones) and an Xtar MCO will run you less than $15…
Yes, that’s because the output is much higher using a 14500, which uses up the stored capacity much faster than running on AA. You’ll notice that high mode on AA is 60 lumen, while it’s 150 on 14500. Compare between high on 14500 and turbo on AA, both are 150 lumens and have almost the same runtime.
KuoH
If it’s a regulated driver, say 2A, the higher voltage in the 14500 will have an easier time keeping an easy current, whereas the lower voltage AA will start struggling to keep up.
I will use this light to hunt rats in farm buildings. I specifically got the zoomie so I could produce a nice even flood of light. I have some other red lights using a WF-501b host but the 18650 drives it too hard and the light is too bright (even with a diffuser). I’m thinking an AA driven Sk68 should be just about right provided I can get about 3 hours out of it. If not, easy enough to pop in a replacement cell.
apples to apples. Both types suffer from losses when used far from their nominal voltage. The nimh doesn’t have a turbo mode and nimh high is more of a medium. The efficiency with a liion drops when converting 1/3 of cell voltage to led Vf. The hybrid driver in the add listed does not regulate both types to the same output but if you look at the lumen-hours of both on high and turbo(total output over time) you can see the advantage switches to the liion(300/285 on high and 300/540 in turbo). I believe a dedicated buck driver would favor the liion much more.
I’m a bit suspicious of the numbers for that light since an XML-2 U2 needs 700 mA to output 300 lumens with no losses and there isn’t liion 14500 cell made with 1260mAhr capacity(1.8x 700).
A AA Eneloop 2500mAhr cell has a nominal capacity of 3Whrs and an 800 mAhr liion 2.96Whr so each needs to be paired with a driver that optimizes that cells characteristics over the output range.
I do find it humorous that it calls an output “turbo” with less than 1A t the LED.