Hey Mooch, I don’t disagree with you, I think we’re generally in agreement. Let me clarify that I’m not claiming there’s some agreed upon spec regarding cycle life rating, it’s why I used the word “defacto” and maybe I should have been less specific in saying; “From what I’ve seen.”
Maybe my experience is has been somewhat skewed, but the vast majority of the general “PR spec sheets” I’ve seen for LCO NMC and NCA have shown approx 800 cycles to 80% OAC in recent years. Some do list different curves, but the bullet points have always been at 800 for those chemistries. Vast majority of LiFeXX have been either 2000 to 4000. None of them show enough data or curve variables IMO.
I’ll admit I probably over generalized, and maybe unintentionally exaggerated (unintentionally) for the sake of counterpoint, and to draw attention to the fact that everything in this sphere comes with tradeoffs, and IMO there’s a lot more potential for complexity in chemistries and configurations than many appreciate.
To be clear I wasn’t saying that there are cells listing 800 cycles to 80% OAC with p42a use scenarios at all. That was my point specifically, the p42a specs I saw actually did a good job of being specific at cycle life at those extreme discharge rates. I was saying that a lot of cells, like say 40T’s showed more conservative pulse discharge numbers, but higher cycle life to 80% OAC, and that if they decided to focus on a higher peak discharge with cooling, and sacrificed cycle life, they may perform similarly. That’s pure speculation on my part, you’d know better than me, but it was an attempt at a metaphor, to explain why I felt (as I think we agree), p42a’s are great cells, but not ground-breaking.
For the sake of openness, I have a bunch of p42a’s, and am personally a big fan of them, fully accepting the tradeoffs.
Just to add re: spec sheet cycle life; admittedly I haven’t been in the “power-cell” segment for long. The vast majority of my interest for years before recently getting into esk8 stuff has been powerwalls and off-grid, so I’ve mainly been focused on higher capacity cells. I’ll openly admit that I’m probably living in a bubble, but I’ve never seen lithium cells that spec’d 250 cycle lives (80% OAC being as I understand, being industry standard for EOL, and thus why the 80% mark being ubiquitous correct?). I certainly trust they do since you mention it Mooch, so clearly it’s just a misconception on my part seeing 800 cycles as kind of a general target for these chems.
I screwed up…my apologies. It seems that 250 cycles wasn’t as common a spec as I remembered. Only three out of thirteen cells I quickly found were spec’d at 250 cycles.
The spec ranged from 200, 250, 300, 400, 500, but I only found one cell over 500 cycles, rated at 1000. Do you remember which cells you saw with an 800 cycle spec? I’d love to compare the conditions they used with the conditions used for other cells.
I’ll go back and look, guaranteed they’ll all be high cap cells with low discharge though. Certainly you’re right that I was overgeneralizing regardless.
I still see all the tesla cells as low discharge power, grate cell cycle, good energy density with is a combination that is grate for tesla cars not ideal for ESk8. For that reason it’s a pipe dream when people thing tesla are going to relice some thing for cars that will dramatically change PLEV. Until thay change direction to PLEV I cant see mutch of any thing been devolved that will revolutionise any thing we currently use.
I agree. Large EV’s do not need power cells and all of them will be high-capacity energy cells. Whatever power output is needed will be reached by placing enough of these energy cells in series/parallel.
ok I will take time to gather current info on cells in the next short while.
As far as I know the previously given timeline said the 4680 cells were supposed to be getting into cars around this time and info from workers have said they are still trying to nail the production lines.
They are often quoted, and ferociously argued over, but IMO cycle life numbers are useless. The conditions upon which they are set vary wildly between cells and often have no bearing on how a particular community uses the cell.
This means the cycle life spec can’t be used to compare different cells and can’t be used to estimate life in a particular application. That results in a not a very useful spec.
But we often want something, anything, to estimate life with so the spec will remain popular.
I’m not sure how to read this chart. Is it just saying discharging at 4.2a and 10a for 500 cycles the cells still have at least 80% of rated capacity? They don’t provide the actual percentage number after 500 cycles?
That is correct.
They can’t list actual percentages because that varies from cell to cell and over time, as they tweak the cell chemistry, it might change. They only list the worst case spec. That’s all most of their large commercial/industrial customers really need though to get an idea if this cell might fit their needs.
I’m sure their big customers can request more detailed data but all of them do their own very, very extensive testing and will derive their own cycle life data.
