Oh. In that link look at the lower set of figures. It seems to drop off by age pretty quickly in the first 750 days to about 95% and then appears to stay flat out from there for as long as the data set goes (few older than 1200 days). Now I am sure with larger n it won’t actually be flat. But pretty shallow for most seems likely.
“Most” is key though. It is also clear in that figure that there are outliers and it would suck to be the one owner whose vehicle is down to 85% before two years.
Potential next generation of batteries:
It’s right there in the table. Room temperature is 25 C. Average capacity loss is 4% per year.
20*4 = 80%. You won’t even get 10 years by these numbers, a battery is considered serviceable once it is down to 80% capacity. This is because after that point the decline becomes exponential.
The footnote about some systems behaving better doesn’t mean that they are immune to the same aging effects, just that they might do a bit better. The Tesla “data” doesn’t include actual individual cell measurements, so we can’t be sure they aren’t hiding true capacity loss in software.
And could be. Maybe they do have stealth software that automatically unlocks more capacity as degradation occurs. Or not. No one has ever reported that such exists but it could be a well kept secret. Or … not. No question that there will be some calendar related loss and that Tesla is not immune to that. And you are free to extrapolate from a graph created to illustrate how higher temperatures impact degradation losses if you wish. Just don’t expect others to be find it compelling.
I would however be interested in your source for the claim that once a loss to 80% occurs “the decline becomes exponential.”
After “many decades” you’re doing to have to replace a lot more than fluids and the lead-acid battery in an ICE. Any rubber and plastic items will likely need replacement as well. Gaskets, too. Unless, I guess, your definition of “stored properly” means “packed in cosmoline”.
As your link shows, stored properly, lithium-ion also has minimal degradation. Keep it cool and at a low but constant state of charge. Although we won’t know about 20 years for a while, many early Roadsters are nearly 10 years old and still going relatively strong.
There is nothing “magical” about the various longevity management techniques. They can easily add up to a factor of 10. Charge control, temperature control, basic chemistry, additives, and general manufacturing quality have a tremendous effect even individually, and together the difference is enormous.
Charts like these may give some indication about the basic shape of the degradation curve, but they are of very little use in projecting real-world lifetime without many other details. It could mean the difference between a 2-year life and 20-year.
Lol. In order for your hypothesis to even possibly be correct, Tesla must have batteries that age at 8 times slower rate than standard commercially available lithium ion batteries. You know, the ones that are in the S. You can feel free to believe whatever wishful thinking you want, but I find this unlikely. I don’t have to posit secret firmware losses, I merely have to point out it’s unlikely they are doing 8 times better than the rest of the industry.
Why do you predict linear degradation but claim exponential? Neither one has any evidence for it, but at least be consistent. A 4% exponential capacity drop per year gives you 44% remaining after 20 years.
By the way, there is some data on the original Roadster here. The data is a little scattered, but look at the “range ideal mi” column for 2008 models without “batt swap”. The original number was about 240 mi. You can see that most of them, even ones 7+ years old at the time, have 200+ mi remaining, and the median is more like 220+. So they have lost perhaps 10% after 7 years. Unless something falls off a cliff, they will make it to 20 years with usable range.
And that’s Tesla’s very first model, with cells that weren’t particularly optimized for auto use. They have made a great deal of progress since then in all departments.
I’m not sure what you think “my hypothesis” is, but I’ll take that as negative on having any source for the claim of exponential decline after hitting 80% capacity.
Meanwhile for your interest. The calendar life of an early Tesla battery (using Panasonic 18650 cells) tested. Too long to watch? Okay but it actually is pretty interesting. Very early little used battery. 5000 miles in an early non-production Smart car then not used since. 5 years in the pack and about 3 just on the guy’s shelf in his garage … which gets 100 degrees sometimes and freezing sometimes. Tested calendar degradation was … 0.35%/year.
No its not magic. It’s just that modern lithium batteries actually do not have so much calendar degradation.
Because exponential degradation is what happens. I was just being charitable at mentioning a linear model but it does go exponential. Also, below 80% capacity is considered dead.
You shouldn’t even be having this discussion, you’ve been alive long enough to see dozens of your gadgets fail from this. I’m in my 30s and I have seen it personally happen dozens of times. Google “lithium battery degradation curve” and you will see dozens of articles on this.
Naturally you’ll claim that I don’t have specific data on the exact cells used in Teslas (especially since the latest model uses batteries that are brand new), but I’m just not interested in that argument. Tesla uses the same chemistry as everyone else. Yes, they did pay researchers to find some improvements, but it will take years to incorporate them.
This is a well known fact, google it yourself. I’m not really interested in a debate, you’ll no doubt claim any particular source I dig up isn’t credible, even though it’s in the datasheets for specific batteries, digikey, battery university, dozens and dozens of scientific papers, etc. It’s a well accepted fact.
I’ll put it the opposite way. Provide 3 credible papers disproving exponential decline* and I’ll paypal you $100.
*doesn’t count if it’s another power law, nonlinear accelerating decline is what I mean by exponential.
Here’s a source, though : https://www.nrel.gov/docs/fy14osti/62813.pdf
And
As you can clearly see, it usually hits a “knee” in the curve and begins to fail catastrophically. It seems to not be exponential*, the first paper says that a second decay mechanism kicks in and the battery actually decays about twice as fast afterwards. *is still an accelerating nonlinear process, though
Exponential is better than linear. 0.96[sup]20[/sup] is 0.44. 100-(20*0.04)=0, as you noted.
If you consider 80% remaining capacity “dead”, that’s your choice, but for many applications it just doesn’t matter. I doubt I’ll keep my Model 3 for 20 years but if it has 80% left after 10 years, I’ll be happy, and the next buyer will still get plenty of remaining use for the next 10 years. It will still have more range than the short-range model, which plenty of people are waiting for. Not to mention a greater range than the Bolt.
I’ve been alive long enough to know that in the bad old days, gadgets usually died from their battery before anything else–often in <2 years. And that today I have many gadgets 5+ years old that are still running fine.
The difference is that the chemistry and charge control have improved dramatically. There’s no more “don’t keep your phone plugged in all the time because you’ll kill it”. It’s handled very efficiently by software now. Same thing for “don’t let it drain all the way” and “don’t let it get too hot”. The gadget shuts down or throttles performance if it enters a state of high degradation. This is also the reason why several years ago, people got in a big stink about non-removable batteries (because they indeed used to suck), and now no one cares because the gadget will go obsolete before the battery dies.
A properly designed EV can stay even closer within its optimal operating range since it has active heating/cooling and isn’t so demanding on max/min state of charge. As noted, most of the time you can stay at a 75% (or 80%, or 90%) charge and get much more lifetime than at 100%.
Page 18 for the NREL paper shows the NCA chemistry, which is what Tesla uses, so it’s at least reasonably representative. And it shows that after 4000 days, and a 50% DoD @ 25 C and 1 cycle/day, there’s still 77% life remaining.
Note that a 50% DoD is huge for a Tesla. And huge for an average American. A typical 12k miles/year is 33 mi/day, or 11% DoD for a Model 3 LR. So 77% remaining life is a very pessimistic estimate.
You’re again, neglecting calendar year loss. So at 4000 days it’s also lost 44% more of it’s capacity, and it has just 33% left.
Except, what was actually happening is that the user needed to drive it the same distance. So this means that as the capacity declines, the depth of discharge is increasing, and the capacity is declining faster, and so on in a cycle of destruction. I was using the word exponential as a shorthand.
Let’s imagine that Tesla is using higher grade cells and thus the calendar year capacity loss is just 2% instead of the average of 4%. Still over the 4000 days (11 years), it lost 22%. Which means those 50% DoD cycles are actually now approaching 100% DoD cycles, which again, means no more battery.
And you get something like this. This is from a Leaf, which does have worse battery cooling and a much smaller battery, and in this blog, the owner admits he frequently has to drive to the limit of capacity and return “sucking EV fumes”.
I don’t know where you get that their simulation didn’t include calendar loss. It’s labeled in days, not cycles. Also, you don’t get to magically add 44% loss because some random other page talking about a different chemistry and no projection past 1 year claimed a 4%/yr loss. Not to mention assumptions about linear vs. exponential drops or in general how losses from multiple sources combine (there is no reason to believe that it’s simply additive).
You’re right that the depth of discharge increases as the total capacity decreases, but this is a fairly small effect until the DoD gets rather large. Which it won’t for typical drivers.
The Leaf is a great example of exactly how not to build an EV. It’s frankly embarrassing that they shipped a car like that. There’s all kinds of data that Leafs degrade at a vastly higher rate than Teslas. It would not shock me at all if a Leaf at 2 years was equivalent to a Tesla at 20 given similar driving styles. Active cooling, superior chemistry, much lower DoD for similar drives, etc. all contribute.
As you can see, by late next month you’ll have over four dozen husbands.
And looking at the source (trying to find where in its 30 slides you are thinking it says what you claim) I find the same page 18 Dr. Strangelove finds. Amazingly enough it in fact does NOT show a sudden drastic after hitting 80% capacity. That 50% DOD line maintains what they describe as a “graceful fade”, pretty linear maybe slightly decreasing its slope beyond 80%. No knee in the curve. The knee (to a slope still less steep than its initial slope) occurs with 80% DODs at 80something% remaining because of mechanical factors that occur at that DOD as well as chemical ones.
Most days for most American commuters even a battery sized at 100 mile range will experience a DOD less than 50% as the daily commute is typically under 40 miles.
Yeah, I can understand why you are not interested in debate.
It clearly shows a plot with a knee and an increase in degradation. Also I linked direct evidence from an owner of a competing EV with the same characteristic curve.
I’m not interested in a debate over known facts.
It’s trivially obvious that it’s true because again, if you discharge a battery to 50%, and it loses 10% capacity, your new depth of discharge is now 40%. Which speeds up the capacity loss further and so on.
This is apparent right from the numbers, I need not produce any cites at all except for basic data on lithium ion batteries, which I have done.
And the NREL data above shows additional decay mechanisms begin to kick in, which include mechanical micro fractures. So there are actually several different decay events happening at the same time, leading to the behavior that anyone who’s owned a product based on a lithium ion battery has personally experienced.
Now, yes, if you are super careful, don’t charge it up fully, use EV grade cells, don’t fully discharge it very often either, use active cooling and better management electronics - it’s better. Teslas don’t die in 2 years like laptops and cell phone batteries do sometimes. (and they used to do all the time)
Doesn’t change the basic fact that the fundamental problems have not been fixed. There are improved anodes and cathodes in the lab that promise to fix this entirely. There’s other battery chemistries that don’t have this problem. (Notably, lithium iron phosphate and nickle-iron). But not the type Tesla is using.
