10500 miles, 10% “degradation” already?

[1.21GW]

I’m hoping others read this and see that the mileage are just estimates. Even gasoline fluctuates 1% every 10 degrees, it’s just that you can’t tell 1% on a gas car gauge but you can tell 3 miles) on a Tesla. Set it to percentage and forget it. Heck, since Tesla shows 1/100 accuracy on percentage, or even worse, 1/300th on miles, even that shines a light that the BMS is just an estimate. The phenomenon is just that the data displayed by Tesla has SOOOO much more precision, it highlights the everyday inaccuracies of modern engineering compared to what we are used to. It will get better with time with the car.

All of my ICE cars have a display that shows miles of range

 

[jmaddr]

All of my ICE cars have a display that shows miles of range

But but the mileage an ICE shows is based on previous driving and not the EPA number. It’s based on previous driving history like anyone who used it should realize. The miles till empty in ICE cars is more like the energy app and that’s my point. My recommendation is to display the percentage and then use the energy app if you need miles. Tesla is just causing confusion showing the absolute max you can obtain with ideal conditions by default and front and center.

In my Audi that miles to empty number was not front and center like the ambiguous gas gauge is and had to be selected to be shown. Further, I would consistently see a max miles of low 300s with that shown whereby the EPA attainable range would have been 418 (26 mph highway times 16.1 gallons). Even if we used the combined number for the s5 the mileage would have read 21mpg x 16.1 = 338. Tesla is putting that 418 number front and center to sell vehicles.

Save your sanity and use percentage normally and then check the energy app when you need mile estimation.

 

[AKinDC]

Here’s one interesting think I noticed. I used to charge my LR RWD to 90% all the time, then I switched to 80. After a little more than a year of ownership (and most of that at 80%) I’m down from 293 at 90 to 278. But here’s the interesting thing.
When the car was new and I’d charge to 90, I’d lose some regeneration...I’d get the message, and feel the difference.
Now when I go to 90, that doesn’t happen.
Is it possible that one of the updates actually changed the amount of battery that I can use to try and keep the battery healthier, and that’s where the loss has really come from, not battery degradation?

 

[Sklith]

The best way to tell how much capacity your battery has is to charge it to 100% and drive it down to as close to 0% as you're comfortable with. If you drain your battery down to 3%, you just divide the kWh consumed by .97.

Don't drive fast, best is about 60 mph on a highway to prevent heat loss in the battery pack.

 

[XLR82XS]

Here’s one interesting think I noticed. I used to charge my LR RWD to 90% all the time, then I switched to 80. After a little more than a year of ownership (and most of that at 80%) I’m down from 293 at 90 to 278. But here’s the interesting thing.
When the car was new and I’d charge to 90, I’d lose some regeneration...I’d get the message, and feel the difference.
Now when I go to 90, that doesn’t happen.
Is it possible that one of the updates actually changed the amount of battery that I can use to try and keep the battery healthier, and that’s where the loss has really come from, not battery degradation?

I tend to believe that since I now see 264 @ 90% and a few months ago and 2 software versions ago it was 278-280 @ 90%. I understand why Tesla would limit range with programming to possibly reduce likelihood of long-term degradation. I can also see it is as way for them to limit battery pack replacement costs under warranty.

 

[1.21GW]

I think Tesla is just doing a social experiment by trying to see how much range they can take away before people complain.

(imagine a 20 something programmer typing away, sending updates to random people then with their friends/coworkers drink coffee and check the internet message boards for complaints...)

 

[camalaio]

Here’s one interesting think I noticed. I used to charge my LR RWD to 90% all the time, then I switched to 80. After a little more than a year of ownership (and most of that at 80%) I’m down from 293 at 90 to 278. But here’s the interesting thing.
When the car was new and I’d charge to 90, I’d lose some regeneration...I’d get the message, and feel the difference.
Now when I go to 90, that doesn’t happen.
Is it possible that one of the updates actually changed the amount of battery that I can use to try and keep the battery healthier, and that’s where the loss has really come from, not battery degradation?

I'm willing to bet this is a temperature change, not a software change. Most people have noted that Tesla now limits regen more aggressively than before with the Model 3, not less. You can be limited by regen due to cold at surprisingly high temps (and keep in mind it's your battery temperature, not the "high" of the day - if it sat at 60F overnight and it's now 90F, the battery is probably much closer to 60F).

I guess it is possible they locked out a top portion, but it would naturally follow that regen would need to be limited to match that as well.

The best way to tell how much capacity your battery has is to charge it to 100% and drive it down to as close to 0% as you're comfortable with. If you drain your battery down to 3%, you just divide the kWh consumed by .97.

Don't drive fast, best is about 60 mph on a highway to prevent heat loss in the battery pack.

This is the best answer we can get without directly measuring the battery pack. A slight change for accuracy would be to calculate the kWh from the distance covered and the Wh/mi or Wh/km (you get at least 3 significant digits to work with this way, not just 2).

You can even use things like AC/heat, as those are counted while driving.

 

[djrodtc]

Little update, the car is still showing a Max of 468km, so I’ve gained 20km changing my charging habits to 90% daily.

 

[hgmichna]

Little update, the car is still showing a Max of 468km, so I’ve gained 20km changing my charging habits to 90% daily.

That could have been caused by battery rebalancing, which only begins above roughly 85%.

But if you want to make your battery live longer, you might now go back to a lower level whenever you don't actually need 90%. I prefer a longer-lasting battery over a nicer distance display any time.

 

[camalaio]

That could have been caused by battery rebalancing, which only begins above roughly 85%.

But if you want to make your battery live longer, you might now go back to a lower level whenever you don't actually need 90%. I prefer a longer-lasting battery over a nicer distance display any time.

I will say this every time I see this (nothing against you, just trying to stop perpetuating this [mis]information)

We have no confirmation that balancing occurs only over 85%.
The same document primarily stated 4.0V/cell is the threshold, which occurs at roughly 73% on the screen.
The same document states that 1mV of imbalance can be dealt with every 24h period. It would take weeks of sitting at 90% to correct any significant amount of imbalance, and would not be suddenly corrected after a couple charges to 90%. Weeks! before you'd notice a difference.

Many people have well-balanced packs and only charge to 80%.
If a pack truly has more catastrophic imbalance (what can't be dealt with by normal charging routines), balancing attempts at those correction rates would be absolutely futile since there's a reason for the imbalance (something physically and/or chemically different about one or more of the many bricks in the battery), and balancing cannot correct this.

What I'm trying to say is the information source posted on these forums seems flawed from our perspective. We don't even know what percent they're referring to. For example, the 4.0V they mention is at about 88% of the total voltage swing of the battery (~2.5 to ~4.2V). Voltage does not change linearly with remaining pack capacity though, which is why at this 88% of the voltage range, only 73% energy remains (which is what is shown on the car's display, because that's what matters). Misinterpreting this data is easy since we're not Tesla employees, and perpetuating recommendations based on a misinterpretation (or simply incorrect source data) isn't ideal.

 

[Candleflame]

Quick correction on the calculation: You mixed ideal capacity and your capacity ("if 100% is 75kWh"). This only works if 100% is only reported at 75kWh, but the percentage is relative to your battery's capacity.

If adding 88% added 62kWh, you have very roughly ~70.5kWh usable 100% capacity. That number from TeslaFi can be confounded in many ways unfortunately, but I'll take it as roughly accurate. At new, I'd expect about 74.3kWh is "usable" at 100% (this would rapidly decline for short time, but not very much).

With a 4.5% of total capacity bottom buffer (seems about right from other data), this means a total capacity of about 73.8kWh on your pack. Again, very roughly, and the number can be wrong in many ways.

Strangely, my total capacity is around 74.5kWh (just 0.7kWh more), but reports significantly more range at 100% than yours. This is very interesting to me, and I can't currently think of why this would happen. Gonna have to go pull some numbers and see if I am remembering anything wrong, or calculated something wrong. Additionally, the above numbers imply you've only lost 5%, which doesn't correspond to [email protected]% at all. Data from TeslaFi could just be a bit off, we're doing a lot of extrapolation here.

total capacity of a new car (and whats needed to get 499km of displayes range is 75kwh without the 4.5% buffer.

 

[camalaio]

total capacity of a new car (and whats needed to get 499km of displayes range is 75kwh without the 4.5% buffer.

Not quite correct, sorry to be pedantic but it helps when folks are debating just a few percent of degradation.

Tesla doesn't market the batteries as 75kWh. In the past when they've done this (Model S and X), the actual capacities (even counting buffers) were never what the label said. Better for them to just avoid the topic.

If you take 499km (the old max range which included a top buffer) and 75kWh, you get 150.3Wh/km. Many, including myself for a long time, though this was an accurate way to calculate it but the reported range doesn't use the bottom buffer. Worse, 150.3Wh/km would put you a few percent off what the car is telling you otherwise (which is significantly when discussing degradation).

The more accurate calculation uses today's ranges and software versions.

• My car: Reports range of 486km (302mi). Reported capacity of 73.8kWh.
  • Total capacity, incl. buffer: 152Wh/km
  • Reality (minus buffer): 145Wh/km
• New car: Reports range of 518km (322mi). Unknown capacity.

• Calculated total capacity (via my constants): 78.6kWh (roughly, not actually this accurate)
• Calculated usable capacity (minus 4.5% buffer): 75.1kWh (roughly, not actually this accurate)

The 2020 model year constants are thought to be different than my 2019 though, and these would work out to a total new capacity of about 77.5kWh (with a usable capacity of 74.0kWh). I haven't been able to pull data from a 2020 vehicle yet.

I hope that wasn't too confusing. Accuracy is very important when discussing just a few percent.