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Range Loss Over Time, What Can Be Expected, Efficiency, How to Maintain Battery Health
- Thread starter KK_RedM3
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Think of this extreme thought experiment: You have a (non-EV) battery at 100% charge, every day you consume 20% charge and recharge 19%. You repeat this process until one day you start with 20% charge and use it down to 0% charge. Is this situation more similar to 1 full cycle equivalent (FCE), or is this more similar to 20% * 80 = 16 FCE?
Now think of how we count FCE in an EV, either you count by mileage driven or by adding up how much kWh each time you charge. Both ways are glossing over the fact that you are charging the battery every time you use regenerative braking (like in the thought experiment). Obviously in real-life driving you are not getting 16x FCE worth of usable energy for every kWh you charge the battery. I would estimate maybe somewhere between 1.3x FCE (heavy city-driving) and 1.0x (highway driving) undercounting of charge cycles based on braking composition of driving patterns.
If you are pulling data using something like ScanMyTesla you aren't missing the charging from regenerative braking, as that is all tracked by the car and included in the charging statistics.
To break it down: 7.8% calendar aging * 1.6% cycle aging = 9.27% net degradation.
Cars with 2021 model year and 60k km, degradation will by dominated by calendar aging. Even if we improved cycle aging by 20%, and cut down cycle aging to 1.3%, then the net degradation would be 7.8% * 1.3% = 9.1% net degradation, a 0.17% degradation difference which would be an almost imperceptible difference, not even reaching 1km of range difference. This is not a good example to look at extended cycle aging.
Looking at the same research paper you cited, they test a "real-world" aggressive highway discharge profile with varying levels of regen braking varying from no regen braking to max regen braking.
You can also look at empirical data publish by Tesla themselves, saying a 12% degradation after 200k miles driven. Quick math says with a generous range estimate of sub-300 miles, that's close to 700 EFC, which is ~8% cycle degradation. Throw on another 8% calendar degradation, which is a low estimate IMO, would mean 0.92^2 = 15.4% degradation, versus 12% observed empirically
Overall I think we're saying the same thing, which is that lower cycle depths will reduce cyclic aging. The main thing to keep in mind is that most continuous charge-discharge degradation tests in the lab and how they count EFC, is very different from real-life EV cycling and also how consumers count EFC.
Well, there is research on regenerative braking as well.
ShieldSquare Captcha
The highest regen (unlimited) in these tests had 16% energy regenerated, so thats more than we have in hour Teslas. The driving cycle was the US06 highway driving cycle.
This is the chart showing the win from less degradation due to smaller cycles due to the microcycles that regen give us.
Ignore the 500EFC = 50000km, in a Tesla LR 500EFC= 200K km.
The question was, how much extra do we degrade our batteries due to all small charges that regen does (microcycles):
This is the answer; This chart do not count the regenerated energy. This show us the difference in battery life for regen or not if we exclude the ”earned” energy.
We do not degrade the batteries extra even in this perspective! For low battery temperature with high SOC regen is till better for battery life than no regen.
Hope this is clear enough = We do not need to count the microcycles as they have no measurable impact on the cycle life.
I we look at for example teslaloggers data for these cars, the degradation mostly is higher. IO think Tesla took the teslarati data and used it. It can be questioned.You can also look at empirical data publish by Tesla themselves, saying a 12% degradation after 200k miles driven. Quick math says with a generous range estimate of sub-300 miles, that's close to 700 EFC, which is ~8% cycle degradation. Throw on another 8% calendar degradation, which is a low estimate IMO, would mean 0.92^2 = 15.4% degradation, versus 12% observed empirically
There is a several tests that compare the degradation from constant current at a correct current rate with driving cycles that use variable power and regen etc. The normal conclusion is that these two give the same degradation rate. One reason is, as I showed in the last post that regen does not degrade the battery. Microcycles can be done, they save energy but they do not cause extra degradation.
It should be clear to anyone that both constand current and highway driving cycles gives virtually the same degradation per EFC.
*One note: There is lot more than one example of most things I write about. Often I use quite a few (same) reports as examples, one reason is that not all resports present pictures that is easy to understand.
For the bolded (by me) part:
No, it is not even trying. Actually it was supposed to show the opposite (that calendar aging takes the big bite from the battery), read this post from earlier back up:
Range Loss Over Time, What Can Be Expected, Efficiency, How to Maintain Battery Health
I usually use a mantra: Calendar aging will be the main degrador for at least the first five or eight years.
This is model s p85d, was made 2014-2016. So basically about 8 years old?
If we had 5-5.5% calendar aging the first year, and we could judge the car to have been about 4-5 years old when it passed 150K-200K km?
(it seems like it was only one car that logged this as the data is very close.
If between 4-5 years, the calendar aging would be something like 5*(square root 5) - 4*(square root 5), thats about 1.2%.
5000km would be about 0.25x5= 1.25% the sum should be about 2.45% between 150 and 200K km?
Original range for this car was 407km.
Range a 150K km was 366
Range at 200K km was 356.
10km/407km is 2.46%. Looks so close that it looks rigged but I just took numbers that seems reasonable and the clearest part of the chart.
I guess its a coincidence that it came up this close but in genereal, I have found it to match the research data very well.
After a lot of ”nice” cycles the degradation per cycle often reduce (curve bending upwards) so the degradation per 10000km might reduce.
For the part about Tesla showing 10% at 200K miles, this car had 356/407 = 12.5% at 200Kkm. I havent learned about the degradation thresholds on Model S, ie, the amount the battery can degrade before the range start to decline. It need to be added to this 12.5%.
Yes, thank you for an very interresting discussion. Its really good that you read the research!
This is true - but if it's cold enough that the car heats the battery before charging after sitting through the night, it's also cold enough for temperatures to reduce the rate of capacity loss a significant degree so that you probably don't need to worry about it.
I'm confused, which is it, do you agree with me or not?
The speed of heat dissipation of the battery is not very fast. You seem to be implying that if it is cold enough, that even if someone charges as soon as they get home, the heat dissipation with be so fast that the car will have to start actively heating the battery in excess of what charging will be doing. That is just nonsense.
Or are you saying that the cold induced capacity "loss" because of overnight cold temperatures outweighs or equals any heating loss if you waited till morning to charge? In this case that also makes no sense because any cold induced capacity "loss" is not real loss of capacity, it is a temporary loss of capacity until the battery warms up from driving.
Now, there are caveats with all of this and pros and cons... For example, charging as soon as you get home and then letting the car cold soak all night in the winter will have the effect of reducing your regen capacity due to a cold battery. Some people might not like this but the blended braking option helps the physical drawback of that effect. Doesn't help the brake pads or efficiency but that is another topic.
But yet I have had it happen. Now, I only currently only charge at 16A, but on one very cold day it charged for a few hours after I got home, but then stopped charging and was just heating the battery with all 16A, with the display reading 24+ hours for the remaining 5% charge. (i.e. at the current rate it would never complete, so I just stopped it.)
Yes I forgot to add that as one of the caveats, at lower charging capacity, the disapation can overcome charging heating. I wil lsay that at 240V/30A(24A actual charging) I have never seen it happen for me*, or even get close to that point.
*Now the caveat to the caveat here is that Tesla used to do active heating at a higher temperature for AC charging but they have fixed that...mostly.
But as long as your car doesn't start actively heating right when you plug in, then from a charging power use efficiency standpoint, it is still better than waiting till it is cold soaked and starts heating immediately.
It might be intended only for a battery pack replacement or resolution of some major fault.
Argh! Just when I thought I had it all figured out! But I get it--this makes sense. However...what about the idea that charging in the morning, before leaving, heats the battery for greater efficiency when driving in the cold? Or is that pointless given my commutes are always at least 30 minutes and usually more like 45 or an hour so the battery heats up anyway just from driving?
Its not easy to make a statement that covers all corners.
If you have a tesla with heat pump and octovalve, charging late with high power gives the possibility for the heat pump to use the leftover heat to heat the cabin.
Charging asap after the drive may result in the heat losses leaving the car, and type get nothing at all from the paid energy.
My M3P ‘21 use 200Wh/km or less in -20C if the battery is above 12C and the heat pump use the energy (batt temp going down).
When the battery is too cold and can not deliver energy, the consumption at the same speed / temp is 260 Wh/km.
I charge asap at one place, at one time only: At my mother-in-law’s place I can o ly use the UMC and only at 2-3KW (10-13A /230V). If the battery cools doen when it’s -35C it takes forever to charge up, and its about 250 km home.
All other cases, I charge late.
At work when the car can be parked for a week in -25 to -35C, I plan the charge to be not finished when I leave. I set the charge level slightly above the needed SOC and start the charging so it will be at about what I need for the drive home.
The result is that no battery heat that I possibly can use is waisted before I start the drive.
I would say that if you have a tesla with a heat pump, charge late!
And in some cases, even without a heat pump, you could carge late and by that himder the need for the battery to run the battery heat.
I've had my car, performance model 3, for about a year and a half now, daily driven about 20-45 miles, always starting at 90%, going down to 70-75% each night. Only ever road tripped once, from michigan to florida which was about 3000 miles of supercharging, home charging for the rest. Michigan is pretty cold most of the time so that would definitely be a good thing for keeping battery degradation at bay, as we only have about 2-3 months of serious heat. I did a health test via service menu in the car this morning and Im at 93% original capacity, which seems pretty bad. At this rate, Id be due for a warranty replacement in about 5 years of ownership, so Im wondering, have alot of you guys tested it out yet? Does this make much sense? Wonder if its worth bringing up with tesla seeing as standard seems to be 1-2% per year. With alot of old Model S's reaching 100-200k miles just hitting 90% OEM capacity it seems like its not doing great
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johnny_cakes
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Where did you see 1-2% per year? The data I've seen indicates a lot worse than that, especially in the first year. Teslalogger shows that the average degradation after 1.5 years (assuming 20,000km is driven per year) is 7% for a M3P, so you're right in the middle of the fleet. The good news is that degradation should taper off with the square root of time. So if your degradation is 7% at 1.5 years, it'll be ~6 years before it's 14%. Very unlikely that you'll hit 30% degradation within your warranty period.
It looks like normal degradation given you lose about 5% in the first year. Your state of charge is also typically high never going under 70% which means you'll probably have higher than average calendar aging contributing to higher degradation over time.
No, it says 93% health, not 93% capacity. We don't know what Tesla is measuring and means by "health"...
No. First Tesla won't entertain anything until you hit 30% degradation. Second, for the Model S it was like 5% the first year then 1-2%/year after that. The Model 3/Y seem to have more degradation in the first year than the Model S.
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