Please feel free to offer some education or a link that would be great.
Does he need IMR cells to get 2.8 A? The internal resistance of a good cell may do a lot to limit the current.
No 2.8A is really not much demand at all, if a battery isnt capable of that I’d say its got some other issues (as in needs to be thrown out), even my cheap 16340’s and my eagletac 14500’s can put out 2.8A for a little while, for just about any 18650 2.8A should be easy especially when fully charged.
You can find plenty of good info here - http://budgetlightforum.com/forum/batteries/rechargeable
PLEASE do some research, Li-ion’s in untrained hands can quickly turn into bomb’s, I’m not saying that to scare you and I’m not exaggerating, they can quite literally explode if mistreated. Its not a problem to use them safely and I’m not trying to turn you off of them, the capacity/performance is unmatched but you really really need to know what your doing before you just start using them. I gave my buddy a setup last month but before giving it to him I made him do a ton of research and learn how to be safe.
Looks like a Panasonic 2.400 Ah drops about 0.2 V at 3 amps. O.11 Ohm, if I read the table right, which is not far from the same. You are right, that is less than I expected, much less important than the state of charge.
Cereal_killer is correct of course - I consider an 18650 that can’t give even 2A to be a cell that has reached the end of it’s life.
I can’t remember where I’d normally send people to learn about this stuff, and after a glance around I didn’t find anything truly great. Adafruit’s article on batteries seems accurate and mostly to the point though. It touches on all relevant aspects in terms of capabilities and capacities. You could also check the similar article at Sparkfun.
What’s probably not covered in depth in either of those is safety and the importance of a charger that terminates properly. Since you have a hobby charger I’m assuming that you already have LiPo packs to go along with it. Same stuff applies for both, safety wise. Don’t charge damaged cells. Don’t overdischarge cells and then charge them, don’t get cells to hot, etc.
Just out of curiosity, why don’t you use a fully charged battery?
Yours may not be as bad as some would tell you, if you just charge it to a full 4.2v…
I’m assuming you looked up the part number stamped on the 18650 to get the mAh number. It’s almost meaningless, except as a way of ranking different makes & models. Call it “Marketeering” as opposed to “Engineering”. If you care about “Charge” or “C”, the 2800 tells you your 2.8A driver would be pulling 1C out of the battery, which is a gentle load.
As has been documented thoroughly on BLF, while laptop pulls are a cheap, plentiful source of perfectly serviceable 18650s, there is never a guarantee any of them will be “good”. You have to charge them and test them yourself before you can Know. If you charge it fully and it still won’t give you full Current through your driver, that’s another sign it’s bad.
Also, be sure you clear the little weld-nipples off the ends, as those can prevent good contact…
How do you get “2800mah.”? I thought 2.4 Ah. is as much charge capacity as one can find in a 18650.
I spotted an error there. It says “Power Density: 126 Wh/kg for lithium ion, 185 Wh/kg for lithium polymer”. But Watt hour is a unit of energy, not power. Watt is the power unit.
I would almost bet the thin wires are the culprit…and/or the wires inside the teeny weeny tailcap switch…they aren’t designed to push buckets of current
Hopefully soon we will have a tested and ready to go 15mm SK68 5*7135 driver though (right now it’s in alpha testing)
I will send you to the batteries and chargers section of HKJ’s website. He shows extensive tests with batteries delivering ~3000mAh. His website is somewhat difficult to navigate, but you can click on the 18650 comparator link at the top and compare some modern cells at different discharge currents. From there click on “Individual tests” at the top to look at a full list of the medium to large sized Li-Ions he’s tested. For an example, take a look at the Keeppower 18650 3200mAh (Black) 2014.
Good catch on the units issue with the Adafruit article, you are correct.
He got full current from a high-drain cell and approximately half current from a laptop pull. I would bet against thin wires being the culprit. Thin wires would definitely cause it to drop out of regulation sooner but beyond that…
Also bear in mind he’s got a Sipik SK98 clone there, does that not take 17mm drivers? Actually Google says a 20mm driver, I guess ztugdriver is using a contact board with the 17mm 105c.
I also have an SK-98 clone with an adapter plate that doesn’t get 3.040 A with a Qlite driver. I have thicker multi-meter leads and will measure again tomorrow.
Ah yeah…gotta replace those thin wires
I have a [SH98](http://www.fasttech.com/products/0/10001857/1520403-ultrafire-sh98-1-cree-xm-l-t6-3-mode-910lm-cool(SK98) clone from FT)
Do yourself a favor and get you a load of the 22AWG Soft Silicone Wire (black) (red) nice thing is, the silicon insulation won’t melt from soldering and is VERY flexible
Nip off about 1/32” - 1/16” of the insulation, tin it, solder it to the contact pads, then do the same to the star, now you will get full flow…mine suffered that way too until I not only rebuilt it but changed out those really thin wires
I have a 8*7135 Nanjg with STAR V1.1 firmware on it, on a 20mm adapter plate (I did have a 20mm Texas Pyro OSHPark board till I fried it some how 
) Works like a champ and is VERY bright! (I also put a copper 20mm sinkpad and a XM-L2 T6-4C led on it as well)
I clicked his link, saw the $6.50 and though no way it could be a SK98, “ass”umed it was a SK68…a SK98 for that price is a pretty decent price!
How bad can you fry a PCB like that? Or dare I ask 
To be fair, I didn’t even click on his link until you started talking about thin wires. That really is an OK price, but I’m resisting.
Fry a PCB like what? Don’t follow
lol @ RBD
WarHawk-AVG — I mean that damaging a 105c based board like texaspyro’s board to the point where it can’t be fixed nearly as easily as it was built, especially with a donor 105c on hand, is nearly unimaginable. Did you actually burn traces? Even in that case, a small airwire should get it back up and running.
No…I think I blew the diode that it had on the board, or had a lousy ground or something…I shelved it after it kicked my butt for a few days then just stuck a regular Nanjg into the SH98 host
I actually have 3x of those boards completely built but unflashed, for some reason the ATtiny wont take the firmware…bleh (might have to pull the ATtiny off the board and flash not in circuit)
I now measure closer to 3 amps., at 4.2 V with only slight increase in brightness when I bypass the meter. Are the wires that come on Qlite drivers not thick enough? Put in my kart for my next Fasttech order.
This #7 ought to be #1.
One can check the leads and meter by shorting out the probes against each other at the tail cap and looking at the change in brightness. With my new leads, I see a much smaller change. If the 7135s are really regulating, there should be no change.