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Plaid Battery

mikes_fsd

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May 23, 2014
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With the Battery Day behind us and some of the dust settled I wanted to start a thread on determining some of the characteristics of the new pack for Plaid Model S.

For the calculations I am using the info we have from Tesla.com as well as

Some other notes:
  • Battery Voltage (cell) is determined by the chemistry, since the chemistry has clearly changed (high-nickel) the cell output voltage is going to be different from the current 2170 and 1865(0) cells. Battery Voltage | PVEducation
Lets dip our toes in...
upload_2020-10-2_14-5-14.png


This photo is part of the animation that shows the new "structural pack".
The photo shows 24 cells running the width of the car and 40 cells the length.
  • 24 * 40 = 960 cells per pack
BUT CleanTechnica has a different shot (not sure where they got it from) in an article Tesla's New Homemade Batteries Are In Test Cars On The Road Today
Tabless4680 - 44x25.jpg


This pack shows that the pack has 25 cells running the width of the pack by 44 cells running the length of the pack.
  • 25 x 44 = 1100 cells per pack
First, I think we are seeing 2 pack variants that are already developed being tested.
I believe the larger one to be the Plaid battery pack and the smaller one will be the Long Range pack for Model 3/Y lines.
Anyway, this is just the initial post, but I wanted to clarify where I am starting from (above) and what I am going to focus on in this topic - specifically the larger 1100 cell pack (25x44).

Any additional input would be highly appreciated.
My initial calculations will be in future posts on this thread, and would love to see others input as well.
 

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zecar

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Width or length will likely be a multiple of target voltage. So 24 or 25 works for ~350V. But the first packs will not be 350V. Also, I expect alternating short and long rows, but maybe not.
 
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mikes_fsd

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Width or length will likely be a multiple of target voltage. So 24 or 25 works for ~350V. But the first packs will not be 350V. Also, I expect alternating short and long rows, but maybe not.
I had to find the right tweet that was from Jason (wk057)
upload_2020-10-2_16-28-40.png


This is the tweet that will also help with the calculations down in the posts to follow.
Specifically, he says the new pack will have a pack voltage of 450 with ~108 cell groups.
Since I calculate 1100 cells in the pack I think it is possible that 20 cells are missing from the pack where vertical support was necessary for the "structural battery pack" to give proper structural support throughout the frame of the car.

i.e. instead of I-beams running the length of the pack (a la current model S/X packs) you have support posts - that are the size of cells or smaller - in 20 spots throughout the pack (probably somewhere in the middle).

Edit:
1100 cells - 20 cells = 1080 cells.
And wk057's find of 108 cell groups perfectly fits to 10 groups of 108 cell blocks in the pack.
Nice clean numbers to work with.
 
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zecar

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In practical terms the pack at will need to be chargeable to 100% under public fast charger specifications. So a 450V pack is possible if CCS specs allow that nominal voltage. Tesla's BMS may be programmable outside the range of which it can be used.

Is a 400V CCS charger required to go to 500V
 

byeLT4

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Feb 16, 2017
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I don't think there are any plans yet for the 3 or Y. I'm guessing instead of having the LR version 'outrange' the Plaid, they are dropping the cells necessary to keep the range as even as possible. Current 100 LR is 402 miles, Performance 100 is 'only' 348, or @87% of the LR. 1100x87%= 957, lets call it 960, wow, look how that lines up LOL. Then if someone comes along with an EV with range equal to or more than 520, BAM, 1100 cell LR model comes out at @600 miles. Of course, down the road without immediately taking away from Plaid sales and perhaps generating new LR purchases while keeping competition decisively in the rearview.
 

mikes_fsd

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don't think there are any plans yet for the 3 or Y
Model 3/Y is Tesla's ENTRY level line with a focus on lowest cost possible. I wouldn't hold your breath on them getting the latest greatest tech advancements that the flagships get.
I did not mean to get into model 3/Y battery discussion.
And agree mostly. The smaller pack I described could be the non-performance model S/X pack.

I want this thread to focus on the plaid structural battery pack that Elon confirmed would be in plaid model S.

I haven't had the time to sit down and put all the numbers together for the larger pack, will try to get to it today.
 
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byeLT4

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The Model 3/Y is Tesla's ENTRY level line with a focus on lowest cost possible. I wouldn't hold your breath on them getting the latest greatest tech advancements that the flagships get.

Agreed, but I feel the need to add- 'at least not this time' :p
 

mikes_fsd

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Alright, so the new Plaid Structural Battery pack on the Model S is being advertised today as
upload_2020-10-5_18-44-14.png

Now, with that info we will dive into our first few calculations.
Key points being used throughout:
  • Using the 1100 cell (really 1080 cell) pack configuration instead of the 960 (see my first post in this thread Plaid Battery )
  • Using the info from wk057 reverse engineering the BMS firmware.
    • 108 cell groups
    • 450V pack voltage
    • useable capacity of 109kWh+
    • upload_2020-10-5_18-49-2.png

The chemistry of the battery drives the cell voltage, interestingly enough the 108 cell group configuration leads to these new cells matching the existing Long Range battery cell voltage.
450V / 108 cells = 4.167 V at the cell level.
According TeslaTap that is the "Individual cells are 4.167 volts at 100% SOC" Undocumented – TeslaTap
Same source lists the nominal voltage at 3.6 V at the cell level.
Maybe Tesla is keeping the chemistry in the new cells the same, given that this chemistry has a long track record with billions of miles of data and they are changing all the other aspects (tabless, manufacturing process, size, pack cooling, etc)

Power output...
The Plaid Model S is advertised with 1100+ HP

1100 / 1.341 = 820.28 kW
So, the peak output of the pack is 820 kW.
P = A * V
A = 820 kW / 450 V = 1822 A (max)
The Plaid pyro fuse will need to be rated at 1850+ A to handle the much -- according to Motor Trend when they tested the P100DL Model S in 2017 "The current flowing out of the battery pack and into the two motors peaks at 1,850 amps."

So, the pyro fuse can be a drop in from the existing Ludicrous configuration?


Onward...

According to Jack Rickard teardown of 2170 cells -
Code:
https://www.youtube.com/watch?v=2nhQw7iGukE
2170 cells have following properties
  • Weight: 70 grams
  • Volume: 970 mm^3
  • Capacity: 4.8Ah / 17.3 Wh
  • Density: 247 Wh/Kg
upload_2020-10-5_19-22-19.png


On Battery Day presentation we are told Energy capacity went up 5x (and since supercharging comparisons were to 21mm cells, I am going with 2170 energy capacity as the base)
upload_2020-10-5_19-37-17.png

4.8 Ah * 5 = 24 Ah

24 Ah * 10 (cell groups in parallel) = 240 Ah at the pack level
450 pack Voltage * 240 pack Ah = 108 kWh pack capacity....

Note that is lower than the 109 kWh useable pack wk057 lists from his hacking in the BMS....
Take same cell calculations but keep the pack at 1100 cells and 10 groups of 110 cells per group.
24 Ah * 10 (cell groups) = 240 Ah pack
4.167 V * 110 (cells in a group) = 458.37 V pack

458.37 pack Voltage * 240 pack Ah = 110 kWh useable pack
That is closer to the 109 kWh useable that wk057 found.

C-rate (peak):
For 1080 cell pack / 108 cell groups
Peak current output per cell group is 1822 A / 10 groups = 182 A.
182 / 24 Ah (cell rating) = 7.5
For 1100 cell pack / 110 cell groups
Peak current output per cell group is 1789 A / 10 groups = 179 A.
179 / 24 Ah (cell rating) = 7.45

Are those realistic? How do they compare to 2170 cells?


Vehicle efficiency...
109 kWh / 520 miles = 210 Wh/mi o_O or 4.76 mi/kWh
even taking the full pack capacity...
110 kWh / 520 miles = 211 Wh/mi or 4.3 mi/kWh :cool:

Alright, thoughts? Tear it apart.



I used Battery calculator : Capacity, C-rating, ampere, charge and discharge run-time calculator (energy storage) to generally verify my numbers, but that does not mean my original assumptions and guesses are correct.
 
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mikes_fsd

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I was discussing these numbers with some folks who - like me - are looking to upgrade their 2016 Model X.
I've made one mistake on an assumption.
The cell voltage of 4.167V
450V / 108 cells = 4.167 V at the cell level.
According TeslaTap that is the "Individual cells are 4.167 volts at 100% SOC" Undocumented – TeslaTap
The nominal cell voltage is 3.6 V for 2170 and 1865 cells.
So, to get to nominal cell voltage of 4.167 V, there does have to be a chemistry change in the cell itself.
 

beatle

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Standard 18650 cells go to 4.2v when fully charged, so 4.167 is actually a bit lower. Some batterygate cars are capped at 4.1v though. Nominal is still 3.5-3.7v.
 

mikes_fsd

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Standard 18650 cells go to 4.2v when fully charged, so 4.167 is actually a bit lower. Some batterygate cars are capped at 4.1v though. Nominal is still 3.5-3.7v.
Yes, but cell capacity in Ah is calculated with nominal voltage not 100% SOC voltage.
So, I wanted to correct that.
In order to have a nominal voltage of ~4.167 V there is a chemistry change in these cells.
Peak cell V at 100% SOC would probably be ~4.8 V
 

beatle

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Aug 31, 2019
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Springfield, VA
Capacity in amp hours is exclusive of the voltage, but I think you already know that. Watt/hours would be impacted by voltage changes.

Chemistry changes don't always end up affecting the voltage. The nominal voltage of all the other cells have always been the same, despite significant chemistry changes through the years.
 
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miimura

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Aug 21, 2013
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In practical terms the pack at will need to be chargeable to 100% under public fast charger specifications. So a 450V pack is possible if CCS specs allow that nominal voltage. Tesla's BMS may be programmable outside the range of which it can be used.

Is a 400V CCS charger required to go to 500V
Other manufacturers already use 108S pack structure on their CCS equipped vehicles. Also, I don't know of any DC fast chargers, Supercharger included, that can't do 500 VDC.
 

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