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

[AAKEE]

maybe it was a fluke set of cells? it was a youtube video where someone bought a few cells and tested them. Also the problem with lithium ion is always to determine what voltage counts as a complete discharge and i cant remember what he used. Particularly at low current draws you can quite significantly discharge them which is obviously detrimental to battery health...

I have seen more than one capacity test so it seems correct.
In the test I mentioned good equipment was used and the currebt was 0.2C, which means five hrs for a discharge cycle.
For a tesla LR this would mean about 15kW power, so about 90-100kph or 55mph or something like that so that currebt is also about representative for the use in a M3.

 

[AAKEE]

maybe it was a fluke set of cells? it was a youtube video where someone bought a few cells and tested them. Also the problem with lithium ion is always to determine what voltage counts as a complete discharge and i cant remember what he used. Particularly at low current draws you can quite significantly discharge them which is obviously detrimental to battery health...

When I did a test with my car this summer I was down to 0.39% SOC, the viltage parked was about 3.09V/cell. When driving (not very fast) the voltage was about 3V/cell or slightly less.
About 3V to 2.5V gives an average in the ball park of 2.75V.
Of the measured capacity of about 4950 mah, 4630mah was from 100%(4.20V) down to 3.0V.
This leaves in the ball park of 320mah below 3V to the discharge limit.

0.32Ah times 2.75V = 0.88Wh.
This is 4.89% of the total capacity.
Albet a rough calc, it show us that there is not much capacity left as the buffer is 4.5%.

Also, there would not be a “brick protection” above the 2.5V /cell manufacturer discharge limit, as the cell will not be bricked by getting discharged to the limit.
All specified capacity, and also all discharge tests that go to 2.5V show the “usable capacity above the safe limit of 2.5V.
Any real ”brick protection” will be below 2.5V and not a part of the real capacity.

The capacity below 2.5V will be very, very small as the cell is more or less completely discharged, and the voltage drops very steep.

I think we have data enough to draw the conclusion that the brick protection is a set minimum cell voltage of 2.5V/cell and that there is no specific capacity set. We also know that the energy below 2.5V is more or less none.

 

[Billee]

Is the Watt hour per mile displayed on the center screen based only on electricity consumed by the power train or does it include other systems such as HVAC, power steering, lights, heated seats, etc.?

 

[jjrandorin]

Is the Watt hour per mile displayed on the center screen based only on electricity consumed by the power train or does it include other systems such as HVAC, power steering, lights, heated seats, etc.?

Just driving, at least as far as I remember multiple people calculating.

 

[AAKEE]

Is the Watt hour per mile displayed on the center screen based only on electricity consumed by the power train or does it include other systems such as HVAC, power steering, lights, heated seats, etc.?

Everything is included, but as jjrandorin sys, it only counts when driving.

 

[Jeremy3292]

Yeah, 80% should be ok. Tap the battery to switch to km/mi as well. (Both % and mi/km are good.)

See below. I took multiple pictures.

 

[AlanSubie4Life]

See below. I took multiple pictures.

View attachment 749494

View attachment 749495

View attachment 749496

View attachment 749497

I guess I should have specified taking the pictures when stationary…safer and I think also any delays when updating introduce no accuracy issues.

Anyway, all the pictures suggest an increase of the degradation threshold to above 78.5kWh. And the last picture suggests 78.9kWh.

Notwithstanding precision issues, it looks like most of this change to 358 miles is due to an increase in the threshold as expected. The constant may have changed but probably did not, insufficient precision to say. If it did (I doubt it) it reduced only slightly and accounts for less than half of the range increase.

 

[Jeremy3292]

I guess I should have specified taking the pictures when stationary…safer and I think also any delays when updating introduce no accuracy issues.

Anyway, all the pictures suggest an increase of the degradation threshold to above 78.5kWh. And the last picture suggests 78.9kWh.

Notwithstanding precision issues, it looks like most of this change to 358 miles is due to an increase in the threshold as expected. The constant may have changed but probably did not, insufficient precision to say. If it did (I doubt it) it reduced only slightly and accounts for less than half of the range increase.

Here are some others I took just for more data points. What was the degradation threshold before?

 

[AlanSubie4Life]

Here are some others I took just for more data points. What was the degradation threshold before?

View attachment 749552

View attachment 749555

View attachment 749560

It was about 77.8kWh.

On balance these pictures suggest about 78.5kWh. It could be a little higher but I doubt it is 79kWh. So it does seem like the constant changed slightly.

Interesting anyway. Guess we’ll see what the 2022 EPA numbers look like (some recent data published but have not looked in detail). Maybe they just make late 2021 with 82kWh battery identical to 2022. It is logical I suppose, though not standard. But: It’s also not standard to change battery types soon after a model year starts, like they did in 2021…

What does seem very clear is that there is no change in range. The Energy Display just more accurately reflects available energy.

 

[Jeremy3292]

It was about 77.8kWh.

On balance these pictures suggest about 78.5kWh. It could be a little higher but I doubt it is 79kWh. So it does seem like the constant changed slightly.

Interesting anyway. Guess we’ll see what the 2022 EPA numbers look like (some recent data published but have not looked in detail). Maybe they just make late 2021 with 82kWh battery identical to 2022. It is logical I suppose, though not standard. But: It’s also not standard to change battery types soon after a model year starts, like they did in 2021…

What does seem very clear is that there is no change in range. The Energy Display just more accurately reflects available energy.

Here is my math:

358 - 353 = 5 miles range increase
5 / 353 = 1.416% range increase
77.8 kWh * 1.01416 = 78.9 kWh

So it should be 78.9 kWh that is "shown" to us now via the rated miles (358). As you noted, the energy was always there it just wasn't "shown" to us.

Additionally, the 2022 M3 LR EPA rated range is 358 miles. So it looks like they made the 2021 M3 LR (that have the newer 2170L cells) match the 2022 M3 LR as they have they same cells.

 

[AlanSubie4Life]

Here is my math:

358 - 353 = 5 miles range increase
5 / 353 = 1.416% range increase
77.8 kWh * 1.01416 = 78.9 kWh

So it should be 78.9 kWh that is "shown" to us now via the rated miles (358). As you noted, the energy was always there it just wasn't "shown" to us.

Additionally, the 2022 M3 LR EPA rated range is 358 miles. So it looks like they made the 2021 M3 LR (that have the newer 2170L cells) match the 2022 M3 LR as they have they same cells.

Right, but the images you have generally show 78.5kWh for the degradation threshold (but it's got a fair amount of "slop" on it). But yes, your math is why I concluded a likely ~79kWh degradation threshold. However, there's nothing that stops them from picking a slightly different constant for 2022 which as you say could apply to 2021 vehicles with the larger pack. It's just the miles divided by whatever they choose as the degradation threshold (which looks like 78.5kWh - 79kWh).

And yes, none of this changes actual available energy or range.

 

[AAKEE]

Right, but the images you have generally show 78.5kWh for the degradation threshold (but it's got a fair amount of "slop" on it). But yes, your math is why I concluded a likely ~79kWh degradation threshold. However, there's nothing that stops them from picking a slightly different constant for 2022 which as you say could apply to 2021 vehicles with the larger pack. It's just the miles divided by whatever they choose as the degradation threshold (which looks like 78.5kWh - 79kWh).

And yes, none of this changes actual available energy or range.

The European 2021 LR with the Panasonic 2170L/82kWh battery seem to never have shown more than 79kWh earlier on the energy screen. I wonder if it is a screen only cap or if it was a cap of the battery as a preparation to the introduction of the LG M50 battery showing up here. Its 79kWh, and the WLTP(the US EPA-equivalent) is the same for both the Panna 2170L and the LG M50, despite the capacity is not the same.
For the M3P they did lower the WLTP range from 567 to 547km, for the change to the LG M50 battery and that difference seems to meet the capacity range.

 

[Jeremy3292]

Right, but the images you have generally show 78.5kWh for the degradation threshold (but it's got a fair amount of "slop" on it). But yes, your math is why I concluded a likely ~79kWh degradation threshold. However, there's nothing that stops them from picking a slightly different constant for 2022 which as you say could apply to 2021 vehicles with the larger pack. It's just the miles divided by whatever they choose as the degradation threshold (which looks like 78.5kWh - 79kWh).

And yes, none of this changes actual available energy or range.

Is the remaining 3 kWh the buffer after you hit 0% SOC?

 

[Candleflame]

Is the remaining 3 kWh the buffer after you hit 0% SOC?

model 3 reserves 4.5% of current max capacity as the buffer.

 

[Jeremy3292]

model 3 reserves 4.5% of current max capacity as the buffer.

I think I was confusing different things here.

From the beginning when you purchase your new M3 LR/P you have 82 kWh available. The degradation threshold is set at 79 kWh (round number for purpose of this discussion). The 3 kWh (82-79=3) above the degradation threshold are “used up“ first, which would then leave you with only 79 kWh available at some mileage/point in time down the road. From that point on you would see a reduction in the rated miles when charging to 100%. This would indicate your battery has degraded enough to have less than 79 kWh available. The reserve after you hit 0% SOC is always 4.5% of however many kWh you have available/remaining.

What did I miss?

 

[Candleflame]

I think I was confusing different things here.

From the beginning when you purchase your new M3 LR/P you have 82 kWh available. The degradation threshold is set at 79 kWh (round number for purpose of this discussion). The 3 kWh (82-79=3) above the degradation threshold are “used up“ first, which would then leave you with only 79 kWh available at some mileage/point in time down the road. From that point on you would see a reduction in the rated miles when charging to 100%. This would indicate your battery has degraded enough to have less than 79 kWh available. The reserve after you hit 0% SOC is always 4.5% of however many kWh you have available/remaining.

What did I miss?

you missed that your question was poorly worded. i dont know about the degradation treshold for the 82kwh battery. i would just read it out with SMT and then you know. Its probably 2-3kwh like with the 77.8kwh battery from panasonic (that one has 22km degradation treshold)

 

[AAKEE]

For my 2021 P with the 82kWh battery the degradation threshold is about 80.7kWh.

I need 80.7kWh to see 507km range. Above 80.7 up to 81.3, it shows 507km. I did see 508-509km as well, but with even higher nominal remaining.
Below 80.7 the range is shorter.

 

[AlanSubie4Life]

From the beginning when you purchase your new M3 LR/P you have 82 kWh available

No, for the LRs it's closer to 79kWh, with FPWN value of 82.1kWh. The 82.1kWh is just a nominal value; it's not clear why it is set that way or why vehicles don't get to that level. But it's just hard-coded anyway.

If you look in the 2021 thread there are a lot of SMT screen captures from both Performance vehicles (which get to 81kWh) and LR vehicles (which are usually closer to 79-80kWh).

 

[ran349]

I think I was confusing different things here.

The reserve after you hit 0% SOC is always 4.5% of however many kWh you have available/remaining.

What did I miss?

No, the reserve you have left after you reach 0% is 4.5% of your full pack value. However, you many not be able to access much of it, depending on many things, so it's best to assume it's not there, and that 0% means zero left.

 

[Jeremy3292]

No, the reserve you have left after you reach 0% is 4.5% of your full pack value. However, you many not be able to access much of it, depending on many things, so it's best to assume it's not there, and that 0% means zero left.

Interesting. So if I have 100k miles on my M3 and only have 77 "usable" kWh now (for example) due to degradation, you're saying there may not be much "left in the tank" so to speak after 0%. Whereas someone with a new M3 probably has a good bit left after 0% SOC.