Range Loss Over Time, What Can Be Expected, Efficiency, How to Maintain Battery Health

[AlanSubie4Life]

On the call back, he says my battery has degraded 20.3%.

This is a typical Tesla service mess up, it sounds like. If you calculate vs. the SR+ (which is a much more common vehicle), that works out to be 190/240 = 0.791 => 20.9%.

This is not a coincidence, vs. the 20.3% quoted (perhaps your vehicle is actually at 191.3 rated miles, nominal full pack 41.8kWh).

I'd ask him to clarify what he is using for the nominal starting capacity, and whether he is using the SR value, or the SR+ (not 2021) value (48.1kWh vs. 52.5kWh). These full pack values I guess I have about 90% certainty on, within a half kWh or so.

my drmi is now at 188 miles

I noticed this after the fact...was this with a true 100% charge? Or extrapolated?

 

[Phlier]

and whether he is using the SR value, or the SR+ value (48.1kWh vs. 52.5kWh).

Sorry for the dumb question, but I got lost somewhere.... what model is @MACH5FL 's car?

Maybe we could talk him into putting his car stats in his signature?

 

[AlanSubie4Life]

Sorry for the dumb question, but I got lost somewhere.... what model is @MACH5FL 's car?

He said an SR. I could be wrong. He said he never had the promised 220 rated miles, he started at 217 (a few posts back).

picked a new 2020 SR December 2019. At 100% SOC, the rated range was 217. I never saw 220 miles at 100% SOC.

Here's the original post.

 

[bedoig]

Another explanation for this (which has been documented for some vehicle years & models) is that there is a hard cap on the displayed rated miles and in fact you had more energy than 310 rated miles (maybe closer to the equivalent of 317 rated miles) when you purchased the vehicle.

That could certainly explain it too, though it would imply actual degradation is even worse which isn't a comforting thought. Heading toward Nissan Leaf levels here.

 

[MACH5FL]

This is a typical Tesla service mess up, it sounds like. If you calculate vs. the SR+ (which is a much more common vehicle), that works out to be 190/240 = 0.791 => 20.9%.

This is not a coincidence, vs. the 20.3% quoted (perhaps your vehicle is actually at 191.3 rated miles, nominal full pack 41.8kWh).

I'd ask him to clarify what he is using for the nominal starting capacity, and whether he is using the SR value, or the SR+ (not 2021) value (48.1kWh vs. 52.5kWh). These full pack values I guess I have about 90% certainty on, within a half kWh or so.



I noticed this after the fact...was this with a true 100% charge? Or extrapolated?

I just got a call back from Tesla. The rep confirmed that my car ( 2020 M3 SR) is showing a 20.3% battery degradation. I asked him to verify he didn’t mix up my SR model with a SR+. He replied that he didn’t confuse them because the diagnostic test ran already knows the vehicle type. I was like okay. He mentioned that my vehicle is the worst degradation he has personally seen. We discussed my daily charging routine and commute. He said there is pretty much nothing he sees that needs to be changed. He said typically when they have customers with battery degradation issues they recommend charging to a reduced SOC that would fit commuting needs. But, he said in my case, there was really nothing that can be changed. He is going to close out the service appointment scheduled for next week and put some notes in capturing our conversation. I also, asked him to include the 20.3% battery degradation reading. He said he can’t do that. He said they keep that number internally to Tesla. He mentioned when the degradation hits 30% we can proceed with a warranty conversation. Also, the drmi of 188 miles was at 100% SOC this morning. When I do charge to 100% SOC, the car sits at the level mostly less than 5 minutes. I’m definitely keeping an eye on the drmi going forward.

 

[AlanSubie4Life]

I asked him to verify he didn’t mix up my SR model with a SR+. He replied that he didn’t confuse them because the diagnostic test ran already knows the vehicle type. I was like okay. He mentioned that my vehicle is the worst degradation he has personally seen.

What did he say the capacity was?

It's very hard to square his statement with your current capacity being about 41.1kWh, where you started with 48.1kWh available (14.5% capacity loss).

There's not really ambiguity in these numbers; it's what they should see when they hook up their instruments.

But this is good! This means that they'll call it 30% when (if) you hit 168 rated miles (70% of 240 rated miles)! Definitely won't want to quibble with them then!

Also, the drmi of 188 miles was at 100% SOC this morning.

Ok. Adjusted calculations above to reflect this. If you get SMT this is what you should see, 41kWh (there is a small amount of uncertainty with SR vehicles since they are so rare, but it's assumed that 48.1kWh is your starting capacity).

You can always do the Energy Screen method at a high SoC to double check the nominal full pack value. (Projected Range * Avg Efficiency / SoC). Of course, with your pack, it is a software-limited value.

When I do charge to 100% SOC, the car sits at the level mostly less than 5 minutes. I’m definitely keeping an eye on the drmi going forward.

For your car it's less of an issue anyway since the pack is only at 91-92% of full capacity at 100%. Though it probably still warns you about setting to 100% all the time.

 

[Candleflame]

@AAKEE I think we're all in agreement that real degradation happens progressively, but it certainly does appear that the BMS presents it in chunks. Almost like a thermostat hitting a temperature trip point, if you get the gist of that analogy.


That explanation exactly matches what I saw with my car when it was new. There are other possible explanations, of course, but IMO, you guys have this one nailed.

We often use degradation and displayed rated range interchangeably. I dropped like 25 km while driving less than 10 cycles and dropped 15km driving less than 4 cycles. I am personally not convinced i even have 10% degradation, i think a lot of it is software for whatever reason.

Also i dropped by my first 20km directly after a software update and then lost even more after the holiday update. The funny thing is that these hidden updates which are supposed to improve range calculation never increase range....

 

[MACH5FL]

What did he say the capacity was?

It's very hard to square his statement with your current capacity being about 41.1kWh, where you started with 48.1kWh available (14.5% capacity loss).

There's not really ambiguity in these numbers; it's what they should see when they hook up their instruments.

But this is good! This means that they'll call it 30% when (if) you hit 168 rated miles (70% of 240 rated miles)! Definitely won't want to quibble with them then!


Ok. Adjusted calculations above to reflect this. If you get SMT this is what you should see, 41kWh (there is a small amount of uncertainty with SR vehicles since they are so rare, but it's assumed that 48.1kWh is your starting capacity).

You can always do the Energy Screen method at a high SoC to double check the nominal full pack value. (Projected Range * Avg Efficiency / SoC). Of course, with your pack, it is a software-limited value.



For your car it's less of an issue anyway since the pack is only at 91-92% of full capacity at 100%. Though it probably still warns you about setting to 100% all the time.

The service rep did not mention the capacity and I forgot to ask him on this last call. That was one of the questions I asked on the initial call that he did not have a answer for. I use to see the warning about setting to 100% early on in my ownership. But, It's been like 8 months since I've seen the warning last. I pretty much forgot about it until you mentioned it. I knew this car was locked on the top by observing the charging signature with my Charge Point app. It charges at the full charge rate all the way up to 100% SOC. No slow down. I previously owned a 2018 Nissan Leaf SV. When I use to charge that car up to 100% SOC it took like 30 minutes for the charging to complete between 98% to 100% SOC. The charging signature would slowly decrease and have a wave like characteristic. I recently purchased a 2021 MY SR for my wife. It too exhibited the same charging signature for those last few percentage points. I'm still pretty bummed about my 20.3% battery degradation diagnosis by Tesla. But, for now, the car meets my needs.

 

[AAKEE]

It charges at the full charge rate all the way up to 100% SOC. No slow down.

Strange. For the lithium batteries Ive used( in other applications) the first sign of degradation is that they get slow(-er) on the last part of the charging cycle. I think it is the increased internal resistance that decrease the current.
So, having 20% true degradation should mean youre in that state of the battery aging. And the charge would be slower, not quicker in the end.

Have you left it charging to 100% until it stops charging? (”Charge complete”)

It would be very interredting to have information from scan my tesla about the cell voltage and cell imbalance. And of course the nominal full pack value and full pack when new.

 

[AAKEE]

This is what's currently happening to my mid-range. Can you explain a little more about why the "chunks" show up once you start supercharging? Here's my experience. I started supercharging more at the 15k mile point and you can see what happened. I'm at 10% range loss in 22k miles:

View attachment 649933

I think its more or less explained but the BMS can not really know the exact battery capacity without a full discharge followed by a full charge to 100%. So it estimates the capacity. Shallow cycles is good for the battery life, AC charge is good. We can easy understand that the BMS can get after the true degradation if you cycle only 60-40% all the time. Changing the sceme with deep cycles, perhaps 10-90% causes the BMS to get new data, which can cause it to estimate a lower capacity. At the same time, deep cycles wear more than small. And supercharging wear more than AC charging, this together ad up to a quicker change in range.

 

[jyavenard]

Thank you for answering the question.

If you were expecting zero or negligible degradation, then you didn’t understand lithium battery technology or EVs when you made your purchase, which is a shame.

I hope you continue to enjoy your car regardless.

I was expecting degradation. I had read all about it.

5-6% is one thing 12+ is another.

 

[Zcd1]

I was expecting degradation. I had read all about it.

5-6% is one thing 12+ is another.

Let us know when Tesla confirms your actual level of degradation.

 

[Candleflame]

Let us know when Tesla confirms your actual level of degradation.

He doesnt need tesla to confirm it. He can just see it by looking at his rated kms or looking at the displayed remaining range per wh/km at a 100% charge or using scanmytesla.

 

[diamond.g]

He doesnt need tesla to confirm it. He can just see it by looking at his rated kms or looking at the displayed remaining range per wh/km at a 100% charge or using scanmytesla.

Tesla won't care until it hit 30% in the 8 year 100k/120k miles warranty period anyways. So no real point in asking them.

 

[Zcd1]

Tesla won't care until it hit 30% in the 8 year 100k/120k miles warranty period anyways. So no real point in asking them.

This is true, and that level of degradation is exceedingly unlikely to actually occur. (IMHO)

 

[jasdelta]

My 2018 Model 3 has 30k miles on it and at 90% soc shows 259 miles, isn’t that pretty low?
Any feedback would be appreciated.

 

[AAKEE]

So, we know battery degradation is a natural and will happen whatever we do. We might be able to limit the amount of degradation for some of the factors in some cases but not all.
- Small cycles is good, deep cycles is worse. Keeping the cycles small will help.
- High current is worse and small is good. Supercharge when you need, and do not when you dont.
- High SOC wear more when the car is parked, Low is better. Dont charge to higher SOC than needed, and charge as late as possible. Dont fill it up and leave it for the weekend.
- High ambient temps is bad, low is good for storage. The combination high SOC and high ambient is extra bad, so try yo keep low SOC if possible when parked during hot season. As it looks from numeorus tests, this might be the most important factor.

If you need to charge to 100% daily, then do it. If you need to keep the car parked with high SOC, then do it. If you need to use big charging cycles, then do it. Both togheter with all these comes more battery wear than if not so do not expect the lowest degradation on your street.

I guess some have seen the low degradation chart for Model S/X. Looks really good. You see the average normalized red line and think,”Thats cool. I will be on that line too”.
But:
1) Its not the 2170-battery. Its not the same application, or the same BMS.
2) Its average. About half of the S/X guys will be below at each point.
3) Its normalized. The average is smoothed to make a soft bent curve. At some points this curve isnt drawn at the average point. Look at 0 to about 15.000km. The line seems to be below the average at some points.

Some of the S/X guys was at 85-90% between 0-60000km, so they experienced 10-15% degradation quite early.

If you have to go hard on the battery, like the ”If-statements” above on a regular basis, you most probably will not be above that line.
We know battery do degrade, we also know what cause it, and we know why.

 

[AAKEE]

My 2018 Model 3 has 30k miles on it and at 90% soc shows 259 miles, isn’t that pretty low?
Any feedback would be appreciated.

SR? LR? + ?
[EDIT] Just found out, you cant see the signature in the mobile, but its seen otherwise.

 

[AlanSubie4Life]

1) Its not the 2170-battery. Its not the same application, or the same BMS.
2) Its average. About half of the S/X guys will be below at each point.
3) Its normalized. The average is smoothed to make a soft bent curve. At some points this curve isnt drawn at the average point. Look at 0 to about 15.000km. The line seems to be below the average at some points.

Also a significant fraction of people started over 100% (some started below, just like Model 3 owners), so interpreting this data is tricky (it calls into question how the data was gathered, and also how to interpret it even if the data was gathered well). Have to take into account the possibility that very few (or none) Model 3 owners started at over 100%, due to a change in how Tesla treats excess capacity and sets the starting point. I'm not saying I know how this was handled exactly, I'm just pointing out that this is a crucial point when making such comparisons. It makes a difference of potentially 3-4% in perceived capacity loss.

My 2018 Model 3 has 30k miles on it and at 90% soc shows 259 miles, isn’t that pretty low?
Any feedback would be appreciated.

No, that projects to 288 miles, which is not particularly low, especially for that age and mileage (I'm assuming a 310 for the starting mileage here, for an AWD). It's a few miles more than my car (which is at 22k miles, and a similar age), and substantially better than someone I know with a 2018, and several here have reported values in the mid to high 270 range, which seems to be the bottom end of the typical distribution.

So no worries. A little less than 9% capacity loss. There are definitely people in your situation who see less capacity loss, but there are definitely those who see several % more. Seems like (very) roughly 3%-14% at that point should be the expectation, with a few outliers.

 

[jasdelta]

Also a significant fraction of people started over 100% (some started below, just like Model 3 owners), so interpreting this data is tricky (it calls into question how the data was gathered, and also how to interpret it even if the data was gathered well). Have to take into account the possibility that very few (or none) Model 3 owners started at over 100%, due to a change in how Tesla treats excess capacity and sets the starting point. I'm not saying I know how this was handled exactly, I'm just pointing out that this is a crucial point when making such comparisons. It makes a difference of potentially 3-4% in perceived capacity loss.



No, that projects to 288 miles, which is not particularly low, especially for that age and mileage (I'm assuming a 310 for the starting mileage here, for an AWD). It's a few miles more than my car (which is at 22k miles, and a similar age), and substantially better than someone I know with a 2018, and several here have reported values in the mid to high 270 range, which seems to be the bottom end of the typical distribution.

So no worries. A little less than 9% capacity loss. There are definitely people in your situation who see less capacity loss, but there are definitely those who see several % more. Seems like (very) roughly 3%-14% at that point should be the expectation, with a few outliers.

P
many thanks for your helpful reply also the op