sk68 lasts how many minutes with "real" 800mah 14500 battery?

I think there are many clones and versions of the SK68, each of them with different leds and drivers. This means the power consumed by an “SK68” varies based on these differences. This being said, it is impossible to tell you how long it will run on 800mah without knowing the power consumption of your specific unit. Also, power consumed may even vary depending on which battery you use, higher quality batteries delivering higher current and therefore depleting more quickly.

It does sound like the cells you have are less than 800mah. Your light will VERY likely be brighter AND produce usable light for longer with a legit 800mah cell. Curious what brand are the cells your purchased?-

they are GTF 2500mah 14500 from aliexpress. i guess since you cant tell me how long, is 15 minutes of full light acceptable from any given flashlight with 3.7 cell battery?

Measure the tail-cap current of your light with a freshly charged cell to see what kind of current level your drive is pushing. You can use that info to estimate (very roughly) what kind of runtime you could expect.

That’s a typo, the manufacturer meant 250mAh.

It’s not quite that simple. For some high-amp lights on small mah cells, yes, 15 minutes is acceptable. To estimate runtime, one needs to know how many amps the lights draws, and how many mah the cell contains. Then some sort of prediction can be made. To give an estimation with two unknown variables is not possible.

It sounds like you want to know if 15 minutes is acceptable for “your” light. With no supporting information I would say no. And I think the entire forum would suggest you buy a better cell for this light. Not only will it run longer, but it will likely be brighter also. These cells you have are extremely questionable and probably dangerous (think explosion).

heck, i have a light that runs 120ma on LOW mode, and a big 26650 in it… i turn it on at DARK, and turn it off at morning… by morning? it was still 3.7v, having started out at 4.2 ish…

by contrast? theres some light rockets the guys here have made that probably would not last more than a couple minutes, lol

also, lithium batteries capacity (assuming the manufacturer doesnt LIE in the first place, lol) isnt a straight line on a graph. By that, i mean this…

lets say you have a .5amp light…. thats the draw on the battery. You have a 2000ma battery capacity. Simplified wisdom says 500ma (half amp) draw out of a 2000ma capacity battery will yield 4 hours…

also, a 100ma small light? on the same battery? should by this reasoning give 20 hours…

its not linear like that. The battery acts like a higher capacity battery at lower draws, and as if it had less capacity at higher draw.

also theres the matter of capacity vs high rate…a battery rated for 30amp short high draws, will likely have less capacity than if it had been designed and rated for only 5 or 10amp short high draws…

reccomendation and reputation are everything… which the lads here hand out freely, of course.

You should probably be getting 30-40 minutes in high mode from a good cell such as the sanyo 14500P in the average sk68.

I’ve never been able to let any SK68 just sit turned on — like when I tried to use one to light up work in a crawlspace.
They just get too hot fairly fast, in my experience.

And that’s being optimistic!
The first cells I got were less than 200mAh.

I did a runtime test on a sk68 clone with XP-E led a few years ago, as a control for a mod, it lasted about 25 minutes on a Efest IMR 750mAh battery. Here’s the graph from that post:

ROFL! :smiley:

Not so recently, a friend of mine showed me a set of BTY 2500/3000 mAh μAh Ni-MH AA’s. When I asked him why did he believed these were good after prompting him to compare their wheight against an old known brand-name set, he told me he thought the new ones were made “from light alloy”.

Cheers

It’d be interesting to know what kind of tailcap/driving current was pushing that driver.

UltraFire SK68 LED Flashlight w/ Focus Zoom discussion at FT. That one seems nice, a user reports 1100mAh of tailcap current.
Not a single mention about the thermal path on these units. :-/

Cheers

this thread has been a good read. i’ll toss the cells as soon as i get some sanyo 14500 batteries in. i store all my unused radio control lipos in a ammo box just in case.

do these 14500 batteries just swell up or just catch fire if discharged too low?

Underwhelming, to say the least. 3’7V no load voltage is probably at about 35% SoC so, even assuming that you run the light for 12 hours at 120mAh tailcap promedium current, that 26650 of yours seems to be a dog… :person_facepalming:

Cheers :partying_face:

1100mA sounds about correct, I have seen 1.5A for a sk68 clone as well. And with its thin aluminium board, no thermal paste and hollow pill it performs remarkably well, see the graph above.

There’s a gap between what we think how good the thermal should be here at BLF, and what limited heat-path a flashlight without any problem gets away with.

Don’t think so but, deliberately keeping them over-discharged for sufficiently long courses of time may inflict permanent damage to the cells.

Lithium-ion Safety Concerns @BU
Interesting article.

Cheers :partying_face:

By the way, what kind of baseplate are these usually equipped with? 16mm round?

Cheers

16mm MCPCB i think, but it’s been a while since i opened one up.

a 14500 is 14MM in diameter and 50 mm long and circlular O

a 14 50 O

A boost driver in the sk68 means you shouldn’t be running 14500’s in it on high till it’s depleted anyway . certainly not without a meter or without protected cells

add an o to the name and subtract a 0 from the capacity.
one i tested came to 317mah.and comments here lead me to believe that one is better than most.
i have seen sk68 style lights built with nice buck-boost drivers all the way to direct drive li ion only cheapies.
measure current at the tailcap as mentioned earlier.