Welcome to Tesla Motors Club
Discuss Tesla's Model S, Model 3, Model X, Model Y, Cybertruck, Roadster and More.
Register

Tesla's 85 kWh rating needs an asterisk (up to 81 kWh, with up to ~77 kWh usable)

This site may earn commission on affiliate links.
You are mixing recharge event data with charge depleting test. The 85.75kWh is based on charge depleting test. DC side of the battery. Has nothing to do with electricity pulled from the wall.

Humm, what?

The value is 95kWh from the wall... and in infers 85kWh from the pack.

You really think the EPA installs a shunt on the HV loop and measures power coming out of the battery?
 
  • Like
Reactions: Cloxxki
Humm, what?

The value is 95kWh from the wall... and in infers 85kWh from the pack.

You really think the EPA installs a shunt on the HV loop and measures power coming out of the battery?

First 85.75 kWh is *NOT* inferred from 95.507kWh recharge event energy, it is calculated independently from it and has nothing to do with this value. Please go back and read my original post carefully.

95.507 kWh recharge event energy is measured during **charging** on the input of the battery and has nothing to do with losses in he circuit, you should stop repeating that it does - it does not.

The 85.75kWh is calculated based on parameters measured during **discharging** the battery, average voltage and AH capacity.

Once again, as I pointed out in the previous post, you are confusing data obtained during charging with the battery discharge data.
 
Last edited:
  • Disagree
Reactions: MP3Mike
You realized the first thing that guy said is "Can bus data from a new 85D with only 300km on odo.". 300km = not a single cycle on the cell. AKA.. the BMS has no clue.. and probably assumes a static value.. a default value. We can't know cause we don't have access to the BMS code but it must start with some sort of value right?

I have CAN readings from my 85D at around 3700kms (around 10 cycles)and I had around 82kWh total.
The problem is similar 18650 cells have a drop from 3100 mAh to 3000 mAh (3.2% loss) within 5 cycles. That means within 5 cycles a 85kWh would drop to 82kWh. How do you know that drop is from BMS calibration (and the pack never having 85kWh capacity when new) and not from this factor.
Tesla's 85 kWh rating needs an asterisk (up to 81 kWh, with up to ~77 kWh usable)
 
  • Like
Reactions: transpondster
Humm, what?

The value is 95kWh from the wall... and in infers 85kWh from the pack.

You really think the EPA installs a shunt on the HV loop and measures power coming out of the battery?
The EPA (or rather the tester, most tests are not done by the EPA) doesn't typically need to do so. They rely on the CAN bus signals if it is available, but if it is not they may need external equipment (see part about instrumentation below).

"Power analyzer used to track electrical energy flows – during testing and charging
• Minimum: Terminal voltage and total battery current running through main traction battery pack"
http://www.cse.anl.gov/us-china-workshop-2011/pdfs/vehicle testing/EV Testing Procedures in the US - Mike Duoba.pdf
https://energy.gov/sites/prod/files/2016/06/f33/vs030_stutenberg_2016_o_web.pdf

This gives them the instantaneous power coming out of battery as well as realtime DC consumption. The EPA test based on the SAE J1634 test procedure measures discharge power and charge power separately. They are not back calculating from an AC only test. The DC number and AC number is measured separately.

This is the data collected during the dyno tests (from an older copy, but should still be valid):
"4.11.1 Battery voltage versus time
4.11.2 Battery current versus time
4.11.3 Vehicle speed vs time
4.11.4 Distance vs time
4.11.5 Battery temperature vs time
4.11.6 Battery power versus time"
https://energy.gov/sites/prod/files/2015/04/f21/etatp3r2.pdf

There are some shortcuts they take so they don't have to do hours of testing (for vehicles with large batteries). They measure the battery capacity at a higher 55mph constant speed and then extrapolate cycle efficiency and total range from the DC consumption. They aren't relying on BMS reported SOC. These kinds of shortcuts are impossible if they relied completely on AC energy measurements as you suggest.
https://energy.gov/sites/prod/files/2014/03/f13/vss094_duoba_2013_o.pdf
 
First 85.75 kWh is *NOT* inferred from 95.507kWh recharge event energy, it is calculated independently from it and has nothing to do with this value. Please go back and read my original post carefully.

95.507 kWh recharge event energy is measured during **charging** on the input of the battery and has nothing to do with losses in he circuit, you should stop repeating that it does - it does not.

The 85.75kWh is calculated based on parameters measured during **discharging** the battery, average voltage and AH capacity.

Once again, as I pointed out in the previous post, you are confusing data obtained during charging with the battery discharge data.

I am curious what @MP3Mike found in the post above to disagree with. These are just factual statements.
 
The EPA (or rather the tester, most tests are not done by the EPA) doesn't typically need to do so. They rely on the CAN bus signals if it is available, but if it is not they may need external equipment (see part about instrumentation below).

"Power analyzer used to track electrical energy flows – during testing and charging
• Minimum: Terminal voltage and total battery current running through main traction battery pack"
http://www.cse.anl.gov/us-china-workshop-2011/pdfs/vehicle testing/EV Testing Procedures in the US - Mike Duoba.pdf

Well, they do seem to actually install a shunt on the HV loop (see page 5).... ! I was wrong about that one. That's actually pretty surprising ;)


The problem is similar 18650 cells have a drop from 3100 mAh to 3000 mAh (3.2% loss) within 5 cycles. That means within 5 cycles a 85kWh would drop to 82kWh. How do you know that drop is from BMS calibration (and the pack never having 85kWh capacity when new) and not from this factor.
Tesla's 85 kWh rating needs an asterisk (up to 81 kWh, with up to ~77 kWh usable)

Yes, this could also be a factor here (might explain the initial value from the BMS). The same rationale applies though.. if you lose 3.2% of your capacity within 5 cycles, is it OK to call the pack having the full capacity knowing that the actual capacity after less than a month of ownership will be less than that?

First 85.75 kWh is *NOT* inferred from 95.507kWh recharge event energy, it is calculated independently from it and has nothing to do with this value. Please go back and read my original post carefully.

I'll have read it back 2 or 3 times already. I've just read another time just for the sake of the argument and I just realized that the 85.75kWh value is coming from the Ah value * average voltage. You know that cannot be used as a real mean to compute W-h values on Li-On cell right? The only real way is to integrate the curve. That thing isn't linear. It plunges abruptly in the last few SOC%... and if you pull a constant current from the cell and average voltage over time, the average voltage will be higher.... and using avg(V) * Ah will over calculate the value of the capacity.

If the voltage curve was linear... starting at 300V and ending at 400V.... in a straight line. Then you could use the average (350V) * measured Ah... but it's not as easy when your voltage curve is wacky like this : http://www.batteryspace.com/prod-specs/NCR18650B.pdf (this is NCR18650B which is not exactly what is in the S.. but is representative for the voltage curve)
 
  • Like
Reactions: jaguar36
I'll have read it back 2 or 3 times already. I've just read another time just for the sake of the argument and I just realized that the 85.75kWh value is coming from the Ah value * average voltage. You know that cannot be used as a real mean to compute W-h values on Li-On cell right? The only real way is to integrate the curve. That thing isn't linear. It plunges abruptly in the last few SOC%... and if you pull a constant current from the cell and average voltage over time, the average voltage will be higher.... and using avg(V) * Ah will over calculate the value of the capacity.

If the voltage curve was linear... starting at 300V and ending at 400V.... in a straight line. Then you could use the average (350V) * measured Ah... but it's not as easy when your voltage curve is wacky like this : http://www.batteryspace.com/prod-specs/NCR18650B.pdf (this is NCR18650B which is not exactly what is in the S.. but is representative for the voltage curve)

The voltage curve IS nearly linear for the range the battery pack is operated in. Take a look at my other post that contains both integrated and calculated battery capacity for Model 3 (EPA data), they match very closely. The difference between two is in hundredth of a percent. Here is the snapshot from the post mentioned above, with two values, first integrated and second calculated highlighted.

So the 85.75 kWh calculated for S85 is most certainly an accurate number.

upload_2017-11-30_12-33-2.png
 

Fair enough, that's for the model 3. Do you have the exact same values for the S? The "Charge depleting test"

This is what you posted :

upload_2017-11-29_12-58-54-png.263519


Unless I can't read... I don't see any integrated Amp-hours value... All I see is average system voltage (350) and that's it. In fact Integrated Amp-hours is at 0! The other values, "system end state of charge watt-hours" is ALSO zero.

Can you just share the full document from the EPA, I feel like I'm missing something.

This for example :

upload_2017-11-29_12-53-5-png.263517


Doesn't seem to be coming from an EPA document. It looks a spreadsheet

You keep mentioning that the EPA measured discharge value, just post a link to a PDF and everyone will be able to see by themselves.

Speculating here since I don't have the model S's document : maybe they never measured the actual DC Wh coming out of the battery back in 2013 on the model S ?
 
Yes @llavalle, you do seem to have a problem with reading. I linked to my other post, to Model 3 EPA data, didn't you read my post? Here it is again, with the highlight:

Take a look at my other post that contains both integrated and calculated battery capacity for Model 3 (EPA data), they match very closely.


So your objection that my calculated value for MS not accurate is not valid. The difference between two values is negligible. Example for Model 3 data shows that.

As far as the Battery Energy Capacity for MS, it was shown in my original post on S85 here it is again:

upload_2017-11-30_13-11-50.png
 
Last edited:
  • Disagree
Reactions: jaguar36
Unless I can't read... I don't see any integrated Amp-hours value... All I see is average system voltage (350) and that's it. In fact Integrated Amp-hours is at 0! The other values, "system end state of charge watt-hours" is ALSO zero.

Can you just share the full document from the EPA, I feel like I'm missing something.

This for example :

upload_2017-11-29_12-53-5-png.263517


Doesn't seem to be coming from an EPA document. It looks a spreadsheet

You keep mentioning that the EPA measured discharge value, just post a link to a PDF and everyone will be able to see by themselves.

Speculating here since I don't have the model S's document : maybe they never measured the actual DC Wh coming out of the battery back in 2013 on the model S ?

I highlighted all numbers used in the quick spreadsheet calculation in my original post. Here is the recap: 95.507 kWh, 245 Ah, 350 V come from the EPA document, each number was highlighted in my original post. 85.75 kWh and 0.8978 are calculated values, as stated in my original post, which also explained how the calculation was done.
 
Yes @llavalle, you do seem to have a problem with reading. I linked to my other post, to Model 3 EPA data, didn't you read my post? Here it is again, with the highlight:

Lol, no need to attack me personally. I was saying that while you did post all of the information for model 3 (integrated values and so on)... you never posted any document that had those value for the Model S.

Just link me the source of your data for the model S in 2013!

Meanwhile, I managed to find this document covering 2017 models.

Page 2 :

upload_2017-11-30_13-15-3.png


Weirdly, while no 85kWh model was available in 2017, the 3rd page still states "battery energy capacity : 245". Where exactly is that coming from?!

upload_2017-11-30_13-13-42.png



The test for the P90D - again no battery capacity. Integrated or otherwise.

upload_2017-11-30_13-17-11.png


Recap for those who don't want to read the whole thing. Recharge event AFTER the depleting phase :

P90D UDDS : 96.65
P90D Hwy : 96.46
P100D UDDS : 111.47
P100D Hwy : 111.88
60D UDDS : 73.45
60D Hwy : 71.68
75D UDDS : 84.48
75D Hwy : 84.65
90D UDDS : 96.08
90D Hwy : 96.66
100D UDDS : 113.201
100D Hwy : 113.201
 
I highlighted all numbers used in the quick spreadsheet calculation in my original post. Here is the recap: 95.507 kWh, 245 Ah, 350 V come from the EPA document, each number was highlighted in my original post. 85.75 kWh and 0.8978 are calculated values, as stated in my original post, which also explained how the calculation was done.

That's the thing.. that 245 value doesn't have any real source. All of the EPA's document, including the one I posted above (MY2017, no 85kWh battery) have 245...

Can you provide me with a document that states how the 245 came to exists?
 
Lol, no need to attack me personally. I was saying that while you did post all of the information for model 3 (integrated values and so on)... you never posted any document that had those value for the Model S.

Just link me the source of your data for the model S in 2013!

I did not attack anybody. I showed source for each number I used for S85 MY 2013 - twice!

The original document here.
 
Last edited:
245 is Battery Energy Capacity in Ah.

I know. What I'm pointing out is that this value, "245" has been in ALL certifications documents from the SAE since 2012. In all model years.. even 2017 when the 85kWh pack isn't available anymore.

It also looks weird. "245". not "244.12" or "245.79".... just 245.

Let's take the data you posted for the model 3 :

upload_2017-11-29_17-50-13-png.263581


230. OK, let's say this is 230Ah.

This is also from Model 3 :

upload_2017-11-29_17-51-51-png.263582


Integrated Amp-Hours : 222.81.


230 vs 222.81.

Where is that 230 coming from? (and I don't mean it's coming from the document).. what I mean is that there is no explanation of what that means. Manufacturer provided number perhaps? IDK... but even if the EPA installs a shunt to measure the storage capacity of the battery.. they can only measure the usable part.. the the whole thing.

==>Can we agree on one thing for model 3 ? : The testing facility that did the measurements on the UDDS test measured 222.81Ah by integrating the area under the curve. That's the USABLE part of the battery. That's an undeniable, measurable value. 222.81Ah

Ok, back to model S now.

We have the first value, 245 (which, weirdly is the same for all MY). Ok, for the sake of the argument, let's assume that it's for the 85kWh model. Where is that second value, the integrated amp-hours value for the Model S.

I've yet to see a document which has the integrated amp-hours value of a 85kWh model S or X.
 
Yes, this could also be a factor here (might explain the initial value from the BMS). The same rationale applies though.. if you lose 3.2% of your capacity within 5 cycles, is it OK to call the pack having the full capacity knowing that the actual capacity after less than a month of ownership will be less than that?
Yes, you can make that argument. But I think there is still significant difference between Tesla providing a 85kWh (and then it wears down to 82 kWh shortly) vs Tesla providing a pack that was 82kWh from the start.
 
Integrated Amp-Hours : 222.81.


230 vs 222.81.

Where is that 230 coming from? (and I don't mean it's coming from the document).. what I mean is that there is no explanation of what that means. Manufacturer provided number perhaps? IDK... but even if the EPA installs a shunt to measure the storage capacity of the battery.. they can only measure the usable part.. the the whole thing.

==>Can we agree on one thing for model 3 ? : The testing facility that did the measurements on the UDDS test measured 222.81Ah by integrating the area under the curve. That's the USABLE part of the battery. That's an undeniable, measurable value. 222.81Ah

Ok, back to model S now.

We have the first value, 245 (which, weirdly is the same for all MY). Ok, for the sake of the argument, let's assume that it's for the 85kWh model. Where is that second value, the integrated amp-hours value for the Model S.

I've yet to see a document which has the integrated amp-hours value of a 85kWh model S or X.
Yeah, I would take the round numbers with a grain of salt. That is likely just a manufacturer provided number. The test itself only measures usable energy (specifically what is required for car to keep up with drive cycle; so if car enters a limp mode, that part is not counted, even though technically the car can still drive some distance).
 
I know. What I'm pointing out is that this value, "245" has been in ALL certifications documents from the SAE since 2012. In all model years.. even 2017 when the 85kWh pack isn't available anymore.

It also looks weird. "245". not "244.12" or "245.79".... just 245.

Let's take the data you posted for the model 3 :

upload_2017-11-29_17-50-13-png.263581


230. OK, let's say this is 230Ah.

This is also from Model 3 :

upload_2017-11-29_17-51-51-png.263582


Integrated Amp-Hours : 222.81.


230 vs 222.81.

Where is that 230 coming from? (and I don't mean it's coming from the document).. what I mean is that there is no explanation of what that means. Manufacturer provided number perhaps? IDK... but even if the EPA installs a shunt to measure the storage capacity of the battery.. they can only measure the usable part.. the the whole thing.

==>Can we agree on one thing for model 3 ? : The testing facility that did the measurements on the UDDS test measured 222.81Ah by integrating the area under the curve. That's the USABLE part of the battery. That's an undeniable, measurable value. 222.81Ah

Ok, back to model S now.

We have the first value, 245 (which, weirdly is the same for all MY). Ok, for the sake of the argument, let's assume that it's for the 85kWh model. Where is that second value, the integrated amp-hours value for the Model S.

I've yet to see a document which has the integrated amp-hours value of a 85kWh model S or X.

The difference between 230 and 222.81 is the difference between the manufacturer stated Battery Energy Capacity (total) and End-SOC Battery capacity (usable). I intentionally provided this juxtaposition in my post on M3 EPA data here.

The same is true for S85 - the 245 is manufacturer stated Battery Energy Capacity (total). The second value, for the charge depleting range was not provided. So my point is that manufacturer stated kWh rating of the battery than, as I pointed in my original post is 245 x 350 = 85.75 kWh. Backing out 4kWh for anti bricking protection results in S85 usable capacity of 81.75kWh, right in the range which you mentioned (81-82 kWh).
 
The difference between 230 and 222.81 is the difference between the manufacturer stated Battery Energy Capacity (total) and End-SOC Battery capacity (usable). I intentionally provided this juxtaposition in my post on M3 EPA data here.

The same is true for S85 - the 245 is manufacturer stated Battery Energy Capacity (total). The second value, for the charge depleting range was not provided. So my point is that manufacturer stated kWh rating of the battery than, as I pointed in my original post is 245 x 350 = 85.75 kWh. Backing out 4kWh for anti bricking protection results in S85 usable capacity of 81.75kWh, right in the range which you mentioned (81-82 kWh).

Ok so we agree that the 245 is given by Tesla. 350x245 = 85.75kWh. That means that Tesla is providing a Ah value that matches the sticker on the battery. 85kWh. No surprises here.

May I quote you :

[...]
But most importantly, it has no bearing on the capacity of the battery which is given by EPA document as 85.75kWh, not 80.7kWh as claimed by OP.
[...]

Let's recap what we have as numbers for the S (using EPA instead of testing facility for simplicity)

  1. Tesla provided data to the EPA that stated the capacity of the pack was 245Ah
  2. During the "charge depleting hwy", the EPA measured the "Average System Voltage" at 350V
  3. After the discharge test, the EPA measured the "Recharge Event Energy" at 95.507kWh charging at 240V
  4. We don't have the integrated amp-hour value of the depleting test

Using these 3 numbers you calculated the following :
  • (350V * 245Ah) = 85.750kWh.
    • Average system voltage during an actual depleting test multiplied by manufacturer's provided value in Ah
  • 85.750kWh / 95.507kWh = .8978.. aka 89.78%


Your whole argument was based on "The EPA document proves that the car has 85.750kWh".. and my conclusion is that is false.

The EPA document states that they measured 350V as an average system voltage and it took 95.507kWh from the wall to bring back the battery to 100% after the test was finished. . It NEVER mentions an actual usable capacity of the pack, an efficiency of charging or measured Ah during the test.

If you still believe that the EPA document for the S has a measured Ah or kWh (pack wise), just point me to it... cause I just don't see it.
 
  • Like
Reactions: wk057