18650 Drain Rates

[vargose]

I understand the desire to want to have the option for a full 1000ma for each LED. But be careful. You'll still need something to limit the current to that for each LED. The potentiometers won't be enough. On a potentiometer's highest setting there is almost no resistance. If you run an LED off that with nothing else to limit the current, you will blow your expensive LED.

But they are right on the color mixing. The only time you'll get to a full 3A is if you are running red, green, and blue at the full 1000ma. Red is most likely going to be pulled down abit anyway, unless you are a pink kinda guy.

I honestly think you'd be better off running all three together off a single 1A source, and potentiometers off that. The single colors will be at their brightest, and the mixes will be about the same brightness. The other way, you'll end up with really bright mixes and standard single colors. I'd go for equal intensity if I were you. Then you won't have to worry about heat or low battery life.

[PhoenixReborn]

The problem is the only way to get true, full color mixing is to have 3 buckpucks, 750mA each (ledengines), or 1000mA each (rebels). Im sure you already know that blue is the dimmest color, and having the ability to make them all go to max really helps to get the brightness or dimness you truly want. And now that tim has 18650s, having the max drain rate helps.

[DarthFender]

Phoenix,

According to one website selling TrustFires, the max drain current is:

- Maximum discharge current: 1.5C

I don't know what the "C" designation is, but I hope this helps. Perhaps one of our many EE's can shed more light on what the "C" stands for and how that translate to mA.



Good luck with your project.

[Novastar]

@Darth Fender... "C" confused me for a while, but it stands for capacity.

Essentially what this means is... whatever the the capacity is of the cell(s), it can take X times that. Where X is the #.

So... "1.5C" means that you can momentarily (IMPORTANT = "momentarily") draw 1.5 x the CURRENT capacity of the cell setup.

So... let's say at this particular moment in time... your cells (theoretically) have like 2000mA ready at their disposal. Essentially, for a MOMENT... you should be able to draw 1.5 x that particular capacity (C)...
...which would be 1.5 x 2000mA
...which would be 3000mA
...WHICH would be 3A.
...and remember--this is only for a few moments. You should probably not draw the max "C" for much longer than maybe 10 seconds. If that. Just as a general ballpark guess.

You'll find that most 18650 packs often have around 2 to 3C (sometimes more)... being that we usually have:

18650s = ~2200mAh or even ~2600mAh

2200 @ "2C" = ~4.4A (this is an estimation, and they usually say 4A)
2600 @ "2C" = ~5.2A (this is an estimation, and they usually say 5A)

Now also remember... this would be a calculation AT FULL CHARGE.

The whole thing is... as you drain the cells... whether from "normal" draw (~1A?) or "uber" draw (~4A??!)... you deplete the PRESENT capacity of the cells. So... yer mileage SHALL vary.

So... basically what I mean is... you ain't gettin' no 5A draw from a pack that has like 20 minutes left of use on the present charge! You gotta fully recharge, bro.

This is ONE of the reasons (one of the only reasons IMHO) why Li-Ions ~can~ be "not as ideal" in some situations for sabers. Well... for sabers lately. Since more people are demanding more from sabers--i.e. FoC and "hungrier" LEDs, etc. hahahah...

Anyhow. "C" is for cookie and that's good eno... ERRR... "C" is for capacity and that's good enough for me...

"C" is for capacity and that's good enough for me...
"C" is for capacity and that's good enough for me...
"C" is for capacity and that's good enough for me...

Phoenix,

According to one website selling TrustFires, the max drain current is:

- Maximum discharge current: 1.5C

I don't know what the "C" designation is, but I hope this helps. Perhaps one of our many EE's can shed more light on what the "C" stands for and how that translate to mA.



Good luck with your project.

[DarthFender]

Novastar,

Thanks for the information. I think I'll stick with the NiMH batteries I know ad love so well, for now at least. Although I am tempted to try the newer NiZn, they look pretty neat.

[Novastar]

For the record, the "C" drain rates or however you wish to express it... apply to NiMh cells as well. Although those generally have a truckload more "ability" to drain like... I don't know--10A(???) maybe?

While we're talking about that, I've always wondered what the drain rates for most alkalines are. Sometimes I think companies don't list that on the cells (or specs, sometimes) so that... well... you don't know!

To this day, I STILL don't know what the "maximum" drain rate is on a more standard AA Alkaline. Not a bloody clue. Granted... I don't really care, since I think it's pointless to bother with them if you're draining >1A over decent periods of time, heheh. IMHO.