Samsung 30Q - high drain 18650 Li-ion cell's capacity test

[john61ct]

Longevity testing is pretty meaningless when the cells are being abused in every aspect of those factors that affect longevity.

0.4C discharge rates stop at 3.1V, and

0.2C charging stop at 90% of the SoC reached at 4.1V

would be a good testing profile to be able to compare cells apples to apples.

If one is 1200 and the other 700, and they both are comparable in their higher C-rate discharge. . .

 

[MesquiteTim]

How would you rate this cell against the 40T?

Hmmm... Are you serious?)))) 40T is a 21700 cell, by the way
[/quote]

So what! I didn't know that this conversation was locked to 18650 cells. The topic is high drain cells. Why not compare to 21700 cells?

 

[thunderheart]

so really this is not really a high capacity/high discharge cell at all if you want a decent lifespan.

Agree and disagree at the same time.
1. 15A is somewhere at the bottom of what i call "high-drain range", very close to mid-drain but not there actually. So a 25A or 30A cell would look much preferable
2. Other high-drain cells also don't provide any significant cycle life if being constantly discharged at 15A+ rates so "decent lifespan" and "high rate discharge" don't come together)

 

[ridethelightning]

well, when this cell first out on the market, i did a fair bit of research, and these details somehow weren't very easy to discover :|

it was really marketed as a higher drain capable cell and many people said,with good chemistry for cycle life.

i agree 15A is a lot for a cell to produce, but it should have been sold as a 5amp cell or what ever, not advertised as a hgh drain cell with matching premium on price.
in my packs i probably only do a short 10A peak at the very max, but it makes me wonder if one might be better going for a panasonic 50b or some other low current cell, as perhaps they are much the same thing but the specs of some are just more conservative.

ofcourse the IR is going to be higher with those others. more heat, faster damage to the cell.
I wonder if the heat caused by IR is the main cuase of damage to the cell or if there is other factors more critical?

 

[john61ct]

So what! I didn't know that this conversation was locked to 18650 cells. The topic is high drain cells. Why not compare to 21700 cells?

There are already so many variables.

Why not compare to a 180Ah CALB cell?

Even better would be focusing on a very narrow range of mAh capacity - 1600mAh cells aren't really comparable to 3400mAh cells even within the 18650 form factor.

 

[john61ct]

ofcourse the IR is going to be higher with those others. more heat, faster damage to the cell.
I wonder if the heat caused by IR is the main cuase of damage to the cell or if there is other factors more critical?

Chemical purity, basic QA and physical build quality come to mind.

Restricting to known-good brands helps keep those consistent.

But tweaking the actual chemistry is I suspect the real secret sauce.

IR is such a slippery number to objectify, I think best viewed as another piece of evidence of power density / high discharge capacity

rather than **the** cause.

And certainly **longevity** under a certain high c-rate / high DoD usage profile needs to be actually tested under standardized conditions, no way to just predict it from any one set of specs.