MASTER THREAD: 2021 Model 3 - Charge data, battery discussion etc

[eivissa]

On another note and maybe I missed it, as I usually dont pay attention to this.

We know about the Energy Buffer vs. Rated Range tricks that Tesla is using (0% = 0km and no Range from Buffer / 100% = Full Rated km inkl. Buffer Range).

Now, does this apply to the indication of charges kWh as well? I would have assumed that it doesn't as this would be very misleading, though...

I have tried this with a 2023 Model 3 RWD LFP60 and a 2022 M3P Panasonic 82kWh.

• I've driven both cars to 0% and charged them back to 100%.
• I've noted Nominal Remaining at the 0% start and 100% end.
• I've noted the claimed recharged kWh that the car is reporting.

The difference between Nominal Remaining 0% to 100% and recharged kWh was exactly the amount of the energy buffer. The cars were overreporting the recharged kWh by exactly that amount!

I am not talking about the charge loss from the wall box, but only the "magic" that is happening within the car. Anyone care to compare or enlighten me?

 

[AlanSubie4Life]

The cars were overreporting the recharged kWh by exactly that amount!

That’s correct. That number is not a measured number. Just a scaled number of rated miles. Added (net) miles scaled by the charging constant (so not the energy added of course). And if you use 10 miles on heat or whatever it won’t count that. Of course!

This is at home. No idea exactly how tabulated at Supercharger. I suspect charged amounts are different than screen display. But I have never paid attention.

 

[AAKEE]

On another note and maybe I missed it, as I usually dont pay attention to this.

We know about the Energy Buffer vs. Rated Range tricks that Tesla is using (0% = 0km and no Range from Buffer / 100% = Full Rated km inkl. Buffer Range).

Now, does this apply to the indication of charges kWh as well? I would have assumed that it doesn't as this would be very misleading, though...

I have tried this with a 2023 Model 3 RWD LFP60 and a 2022 M3P Panasonic 82kWh.

• I've driven both cars to 0% and charged them back to 100%.
• I've noted Nominal Remaining at the 0% start and 100% end.
• I've noted the claimed recharged kWh that the car is reporting.

The difference between Nominal Remaining 0% to 100% and recharged kWh was exactly the amount of the energy buffer. The cars were overreporting the recharged kWh by exactly that amount!

I am not talking about the charge loss from the wall box, but only the "magic" that is happening within the car. Anyone care to compare or enlighten me?

Yes, except from @AlanSubie4Life’s answer this also settles the buffer in the LFP question.

Charging 0-100% will include the energy of the buffer.

 

[eivissa]

Thanks @AlanSubie4Life @AAKEE !

I've published my measurements, explanations and conclusions here in the "Akkuwiki".

[Wiki] Akkuwiki - Model 3 / Model Y

Ladeverluste - Anzeige vs. Realität Wichtige Erklärung vorweg: Der Wert „Nominal Remaining“ ist ein CANBUS Wert, den man mit Scan My Tesla auslesen kann. Er gibt die aktuell geladene / verfügbare Kapazität des Akkus an. Bei 0kWh Nominal Remaining ist der Akku komplett entleert, inkl. Energy...

tff-forum.de

 

[eivissa]

Also...here is a first glance at the BYD Blade 7C LFP structural battery pack ;-)

 

[RVAC]

Interesting, didn't certification documents say 55kWh?

 

[AAKEE]

Thanks @AlanSubie4Life @AAKEE !

I've published my measurements, explanations and conclusions here in the "Akkuwiki".

[Wiki] Akkuwiki - Model 3 / Model Y

Ladeverluste - Anzeige vs. Realität Wichtige Erklärung vorweg: Der Wert „Nominal Remaining“ ist ein CANBUS Wert, den man mit Scan My Tesla auslesen kann. Er gibt die aktuell geladene / verfügbare Kapazität des Akkus an. Bei 0kWh Nominal Remaining ist der Akku komplett entleert, inkl. Energy...

tff-forum.de

Very good!

 

[eivissa]

Interesting, didn't certification documents say 55kWh?

Well...funny story...not really!

Since this leak/claim by a German Tesla news publication, I have denied this, as all m calculations pointed towards 59kWh. The claim was also, that this was stated within the type certificate.

Since usually I am the source for this kind of information/leaks I have scanned all my documents to find these 55kWh without success.

So I contacted the authors, as I am also often providing them with information.

Turns out...the weight limit table was a bit...let's call it...miss interpreted:

The 55kWh still spread all around the world in all kinds of Tesla news formats...

 

[AAKEE]

But as the otjer batteries, Tesla has used ”75kwh” in some documents for the 77.8 kWh battery.

Its kind of 55 except the buffer?

 

[eivissa]

But as the otjer batteries, Tesla has used ”75kwh” in some documents for the 77.8 kWh battery.

Its kind of 55 except the buffer?

Yes, true and people do EPA and WLTP calculations based on those 75kWh, which is pointless as the cars are driven until dead in those tests, so the buffer does count in as well.

55kWh was never a real claim. Just someone reading 55 next to BYD on a weight sheet, not realising, that it said 5S for five seater!!!

 

[AAKEE]

55kWh was never a real claim. Just someone reading 55 next to BYD on a weight sheet, not realising, that it said 5S for five seater!!!

 

[TimothyHW3]

The difference between Nominal Remaining 0% to 100% and recharged kWh was exactly the amount of the energy buffer.

Is that news to you? Tesla doesn't calculate the "added" kWh in the battery - they simply get the remaining range in miles/km from the start and the remaining range in miles/km at the end, diff is the "added miles/km" and then they multiply this number with the constant to extrapolate km/miles to kWh and show you "added kWh".

This is done to get a consistent miles/km reading while charging. Otherwise the driver will see that you added too little kWh and that 100% is not 100%.

This has the nice additional effect that it gives you a number closer to what the charger is reporting so we have these bozos that claim their car only has a 1% charging loss, because they read the added kWh and think this is what goes into the battery

 

[voldar]

I put on paper the info from this video :

SOC	kWh added	mins
8% - 100%	54	52+ (45 mins to 99%)
48%-93%	27	23
4%-90%	50	34
15%-56%	24	13
23%-64%	24	13

Maybe some will find it interesting. I am not sure if the added kWh to the battery is the real number and the losses aren't included in it.

 

[voldar]

... we have these bozos that claim their car only has a 1% charging loss, because they read the added kWh and think this is what goes into the battery

I doubt they do that. It's too much for them.
Usually they only look at the range estimation number @100% and they assume that if now they see 264 miles instead of 273 miles, they have a (1 - 264/273) x 100 = 3% loss. Which can be or not be true, based on the type of driving you do.

 

[voldar]

I have tried this with a 2023 Model 3 RWD LFP60 and a 2022 M3P Panasonic 82kWh.

• I've driven both cars to 0% and charged them back to 100%.
• I've noted Nominal Remaining at the 0% start and 100% end.
• I've noted the claimed recharged kWh that the car is reporting.

I wonder, did you also noted the kWh used from 100% to 0% ? I think that number has value too. Do you have them ? Compared against the kWh added, what was the difference ? You could have this way an idea of the losses during charging. Of course, if the trip was on a more or less same level road.

 

[AAKEE]

I wonder, did you also noted the kWh used from 100% to 0% ? I think that number has value too.

If the car was driven directly after the full charge, this will be the net value of the battery capacity. Full capacity - the 4.5% buffer so = 0.955xthe full capacity.

I did drive 100-0% and did get 75.15kWh out (car was parked with sentry of for some 8 hrs in the middle of the two drives). Ehen parking the var said 0.27% SOC, that increased to 0.41% after 10-15 minutes, 0.3 kWh remaining above the buffer.
Added up it was 78.9kWh.
Precisely at the time my BMS was quite off, but I also did a 0-100% charge like two months before, that added 79kWh.
The BMS says the capacity is about 78.5kWh these days, so it all add upp with 79 kWh capacity - 79 kWh carged from 0-100% and about 75.5 kWh net capacity.

Do you have them ? Compared against the kWh added, what was the difference ?

For me, during many checks at home WC at three phases 230V 16A so 11kW, i get about 10% difference between the electric meter before the WC and the delta in nominal remaining.

 

[TimothyHW3]

If the car was driven directly after the full charge, this will be the net value of the battery capacity. Full capacity - the 4.5% buffer so = 0.955xthe full capacity.

There is heat loss you are forgetting. At low speeds minimal, but still there.

Usually they only look at the range estimation number @100% and they assume that if now they see 264 miles instead of 273 miles, they have a (1 - 264/273) x 100 = 3% loss. Which can be or not be true, based on the type of driving you do.

That is exactly what it means - the miles you see at 100% are straight up kWh, converted by the car from miles to kWh. This is how you calculate degradation or BMS misscalibration. That number is not influenced by your driving.

" I am not sure if the added kWh to the battery is the real number and the losses aren't included in it."

They are not the real added kWh, read what I explained above.

If someone has an older Panasonic car from 2018 to about 2020 (the ones with the blue snowflake symbol when the battery is cold) they can easily test it without tools. In the winter when the battery is cold and you get that blocked blue snowflake section, once you start charging the car there is a point where the blue range is being released once the battery gets warm and the car will display more kWh added than the station delivered.

 

[voldar]

That is exactly what it means - the miles you see at 100% are straight up kWh, converted by the car from miles to kWh. This is how you calculate degradation or BMS misscalibration. That number is not influenced by your driving.

That number is based on the BMS readings of the cell voltage (min and max) and when you drive your car 40 miles a day, using about 20% of the battery @ most, in time, the BMS no longer has the right readings. This is why you need to balance the BMS about once a year, if you aren't driving using the battery from 80% to 20% in your daily driving. And yes, it's a fixed number based on an algorithm that has nothing in common with the driving.

To have an idea of the degradation, I'd fill up the battery to 100% then drain it to 5% in a shot, and write down the number I get for kWh used.
Next time, lets say a year later, I'd do the same, in about the same conditions of driving, on the same route, and get another reading of the kWh used. The difference between the two numbers would give me an idea about the degradation.

 

[voldar]

They are not the real added kWh, read what I explained above.

Not sure your explanation is true.
When charging a Tesla on a CCS DCFC - using a CCS adaptor - you can see the kWh the DCFC is giving you and what the Tesla reads as getting into the battery.
I will pay attention next time I do this and I'll let you know.

 

[AAKEE]

There is heat loss you are forgetting. At low speeds minimal, but still there.


That is exactly what it means - the miles you see at 100% are straight up kWh, converted by the car from miles to kWh. This is how you calculate degradation or BMS misscalibration. That number is not influenced by your driving.



They are not the real added kWh, read what I explained above.

If someone has an older Panasonic car from 2018 to about 2020 (the ones with the blue snowflake symbol when the battery is cold) they can easily test it without tools. In the winter when the battery is cold and you get that blocked blue snowflake section, once you start charging the car there is a point where the blue range is being released once the battery gets warm and the car will display more kWh added than the station delivered.

The rating of a battery is normally at relatively low load, like 0.2-0.3C, and the rated output is exlusive heat loss so a 5.000 mAh battery should deliver 5000 mAh ”energy”.

Im quite sure that the nominal full pack or nominal remaining is supposed to deliver the rated energy.
For my drive with an average of 12kW power, thats 0.15C so in this case we shouldnt ”add” any energy for the heat loss.
In general it’s hard to know or estimate the heat loss, in most cases the guestimate will be wrong so I would say that we should use the energy we did get out and instead refer to the circumstances, like “at 80 mph highway” or so.
A battery kept long time at high SOC will have higher internal resistance, which in turn means higher losses.