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Battery Degradation question
- Thread starter robl45
- Start date
Not sure why people are so obsessed with trying to measure (inaccurately by the way) battery degradation in their low mileage vehicles. Simply looking at the stated range next to the SOC % of the battery does not measure degradation. It seems through extensive testing by several sources, the general consensus is there is approximately 10% battery degradation in terms of range at 100,000 miles. For example, check out Kyle Connor’s testing on his YT Out of Spec Motoring for a comprehensive discussion about this topic and stop spreading unfounded and unnecessary hysteria.
AlanSubie4Life
Efficiency Obsessed Member
I agree that actual degradation is hard to measure.
However, from a practical standpoint all that matters is what the BMS thinks is available (since that will determine when the car will shut down), not the true degradation.
Do you have any evidence that this method (rated range) does not directly align with the best estimate of energy remaining by the BMS, as reported on the CAN bus, as outlined here?
zoomer0056
Active Member
Don't care about all the hysteria, real or imagined ... but the Tessie app is awesome!
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Well, most of the degradation doesnt come from the miles the first 5-8 years or so.
Calendar aging is the thing that degrades batteries for the absolute main part the first years. Calendar aging is SOC and temperature dependent. For both, lover is better.
Degradation above 10% well below 100K miles is not uncommon.
Is it $200 awesome?!? I just looked and am stunned at how expensive these apps have gotten. I remember paying $10 or $15 for Stats, 4yrs ago, and being miffed that I couldn't get it on sale for $5.
zoomer0056
Active Member
Recurrent auto is "free" website that will do the same thing. I'm at 4Ys/30k miles in mid M3 RD. Range has slightly gone up this month (warmer?) to put me in bottom of the distribution (was outside of it last month). I charge to 80% unless trips. 95% of the time using 110V. 227/263 initial miles (~14%).
GreenCoffee
Member
I guess I was mistaken then with my 5 year old model 3 at 57,000 that I just thought lost 14% of its range, good to know!
Some of that Recurrent data seems weird to me. I am totally fine that my car is off their scale:
but this sort of thing where my expected range is 303-304miles, when if you look carefully at the above chart, they show 260 and 340, and I am well above the middle of 300. Stats says 310. SMT says 310. Recurrent says 303-304. Weird. And what does 101 mean? And, in another 3yrs, when my car is over 7yrs old, they're projecting I'll lose only 1 mile of range?!?
My car really IS a unicorn.
zoomer0056
Active Member
The scale on the left shows available kWh of the battery. Anything below that average line is a lower capacity battery than average.
Yes I understand.
What I am trying to say is that the degradation is mostly due to time diring the first 5-8 years.
This means, when keepin the same SOC between two cars, of which one is driven
about average and the other isnt driven at all, both will suffer about the same degradation.
A car that was driven less than average have a good chance of getting below the average on that graph as about the same degradation happens anyway.
Some day people will stop focus on miles and look at time also, in that case your car would be much Closer to the average.
Batteries doesnt do degradation by coincidence, they do it in a very predictable way.
Let the battery run down. Let it sleep at all different settings and the net result is:
Not a damn thing changed
Not a damn thing changed
charging limit to 75% will not help much. Charging limit to 50% will help a lot. You have a very long range car with insane power, since you can charge at home, why not set as low as possible?
I found AAKEE's thread as soon as I got my 3. I set my charge limit to 50%, and have < 3% degradation after 10 months and almost none over last 5 months. Since degradation goes as sqrt(time) and according to him there is no interaction of that sqrt() with SOC, then lowering degradation the very first year of ownership will have permanently beneficial effects.
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A car that's driven frequently will very probably have an average lower SOC, so it may even have less degradation that a car that spends most of its life sitting at at 90% being driven infrequently, and immediately charged up after driving.
Yes, We agree.
I even use that as an example sometimes, but in this case I tried explaining to @zoomer0056 that the reason for being below average could be that he has the same calendar aging but less miles driven. So the statement that is the easiest one to swallow was chosen
Exactly. The MSLR still use Panasonic 18650 NCA, I think.
The thing will be to stay below the central graphite peak, that is at about 57-58% for a new NCA battery. (Its masked in the picture by only having data points at 55 and 60% and no one in between.)
As tesla has bottom buffer the on screen SOC is showed slighty lower than the real SOC. For Model 3/Y the buffer is 4.5%. I'm not sure about the new MS/MX but most probably about the same buffer size, This means that the true SOC is about 2% higher at 55% so choosing a on screen SOC of 55% or lower will keep the battery on the good side of that peak, thus cutting the calendar aging in half just by doing this.
Another thing, specially if needing more energy than 55% SOC is to charge late. Setting the charging time to be finisched shortly before the drive keeps the average SOC low, and reduce the calendar aging.
Its possible to charge to just about *any* SOC and still have a low calendar aging, if the car was parked at low SOC and the charging was done shortly before the drive,
For @zoomer0056: I have used this low SOC strategy since my M3P was new december 2020. Now at 60K km (37K mi) I still have very high capacity in the battery, 78.9kWh out of 82kW, the packs "starts at" about 80.5kWh according to the BMS.
The other M3P 2021 is well below. There is more than 30 cars in the data, but only a few with the same ODO reading. The other cars has lost 3 times more range than my car has, so the low SOC strategy works.
There is a lot of research available about this, and the research supports this. There even is research reports on the low SOC strategy reducing the degradation, so it is not hokus pokus or something like that.
Candleflame
Active Member
Not sure if milage makes any difference really.
If you look on teslafi in the highscore table:
368k kms 422 km
314k kms 406km
291k kms 428 km
279k kms 442 km
those all had 499km rated range
I’m not sure if I understand you.
I mean that a car that was driven very little still loose about the same range per month as car that was driven normally or more.
Sonif looking at the ”miles vs average range” in Tessie, you might think there is something wrong with the car but it isnt.
So, I had 3 questions about the Teslafi chart:
• When I look at your data, I see 3 sections, the original flat section up to 39k, representing about 503k original range; then a current flat section from 52k onward, representing about 493k. Then, there's the gradual but steady drop from 39k to 52k. Any externalities that you can think of contributing to that drop?
• Two, that light green line represents only 4 other vehicles? Does that imply that there isn't a lot of datapoints in the Teslafi database?
• Three, your data, when compared to the "fleet" isn't included in the "fleet"?
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