Drivetrain-battery combo performance differences S60, S85, and P85
On the official Tesla Motors forum there was a thread where someone asked where the difference in performance between de S60, S85, and P85 came from. Well, I did some digging and found some answers. I thought these answers where interesting enough to share with TMC. Feel free to kick my $ss if you don't think so :wink:
Anyways, here's my post:
What have we learned so far:
(Side note: Some numbers are approximate (but all are based on actual specs!), however they still give quite an accurate idea of what you can do with each drivetrain / battery combo.)
UPDATE 1 (green)
- more accurate cell count per battery
- increased maximum load current of a single cell to 12.5 A
- replaced 'motor' by 'drivetrain' to avoid motor/inverter discussions
UPDATE 2 (purple)
- more accurate charging voltage (mainly changing the 60 kWh calculation)
Thank you all for the invaluable input!
Comparison drivetrain power output versus battery power output:
* S60: 285 kW vs 227 kW (battery limited)
* S85: 285 kW vs 320 kW (drivetrain limited)
* P85: 350 kW vs 320 kW (battery limited)
Conclusion:
8) Power loss in battery cells (dissipated heat)
The internal resistance of a fresh battery cell is about 100 mOhm (0.1 Ohm)
=> S60: 750^2 x 0.1 = 56 kW
=> S85: (285 kW / 346 V )^2 x 0.1 = 68 kW
=> P85: 925^2 x 0.1 = 86 kW
9) Total energy usage in battery (power output + heat loss):
=> S60: 227 + 56 = 283 kW
=> S85: 285 + 68 = 353 kW
=> P85: 320 + 86 = 406 kW
References:
High Power Wall Charger - Actual DC Volts/Amps Going To Battery?
Battery facts?
Analyzing car efficiency at different power outputs (accelerations) | Forums | Tesla Motors
Model S Options & Pricing | Tesla Motors (may not be the same, depending on your country)
industrial.panasonic.com/www-data/pdf2/ACA4000/ACA4000CE240.pdf
On the official Tesla Motors forum there was a thread where someone asked where the difference in performance between de S60, S85, and P85 came from. Well, I did some digging and found some answers. I thought these answers where interesting enough to share with TMC. Feel free to kick my $ss if you don't think so :wink:
Anyways, here's my post:
What have we learned so far:
(Side note: Some numbers are approximate (but all are based on actual specs!), however they still give quite an accurate idea of what you can do with each drivetrain / battery combo.)
UPDATE 1 (green)
- more accurate cell count per battery
- increased maximum load current of a single cell to 12.5 A
- replaced 'motor' by 'drivetrain' to avoid motor/inverter discussions
UPDATE 2 (purple)
- more accurate charging voltage (mainly changing the 60 kWh calculation)
Thank you all for the invaluable input!
- S60 and S85 have the same drivetrain, but different batteries.
P85 has another, more powerful drivetrain.
- Motor specs (from Tesla website)
Power:
S60: 285 kW - S85: 285 kW - P85: 350 kW (WITHOUT taking battery into account = theoretic)
S60: 225 kW - S85: 270 kW - P85: 310 kW (power WITH battery taken into account = realistic)
Torque:
S60: 440 Nm - S85: 440 Nm - P85: 600 Nm
- Number of cells per battery (each cell has a capacity of approx. 12 Wh, rounded for simplicity's sake)
=> 60 kWh battery has about 5040 cells
=> 85 kWh battery has 7104 cells (confirmed information from Tesla)
- Battery is charged at supercharger at 4.2 V charging voltage per cell
* 60 kWh battery tops off at 352 V
=> 352 V / 4.2 V = 84 cells in series in a single bank
* 85 kWh battery tops off at 402 V
=> 402 V / 4.2 V = 96 3.6 V battery cells in series in a single bank
- Number of banks per battery
* 60 kWh battery has 60 banks of 84 cells
* 85 kWh battery has 74 banks of 96 cells
- Maximum discharge current is 12.5 A per cell (based on 2) and 7))
* 60 kWh
=> 12.5 A per bank of 84 cells
=> 60 x 12.5 A for 60 kWh battery = 750 A
* 85 kWh
=> 12.5 A per bank of 96 cells
=> 74 x 12.5 A for 85 kWh battery = 925 A
- Maximum discharge power at nominal cell voltage of 3.6 V:
* 60 kWh battery:
=> 3.6 V x 84 cells = 302 V
=> 750 A x 302 V = 227 kW
* 85 kWh battery:
=> 3.6 V x 96 cells = 346 V
=> 925 A x 346 V = 320 kW
Comparison drivetrain power output versus battery power output:
* S60: 285 kW vs 227 kW (battery limited)
* S85: 285 kW vs 320 kW (drivetrain limited)
* P85: 350 kW vs 320 kW (battery limited)
Conclusion:
- S60 is limited by maximum battery discharge rate of 60 kWh battery
- S85 is limited by maximum power of drivetrain
- P85 is limited by maximum battery discharge rate of 85 kWh battery
8) Power loss in battery cells (dissipated heat)
The internal resistance of a fresh battery cell is about 100 mOhm (0.1 Ohm)
=> S60: 750^2 x 0.1 = 56 kW
=> S85: (285 kW / 346 V )^2 x 0.1 = 68 kW
=> P85: 925^2 x 0.1 = 86 kW
9) Total energy usage in battery (power output + heat loss):
=> S60: 227 + 56 = 283 kW
=> S85: 285 + 68 = 353 kW
=> P85: 320 + 86 = 406 kW
References:
High Power Wall Charger - Actual DC Volts/Amps Going To Battery?
Battery facts?
Analyzing car efficiency at different power outputs (accelerations) | Forums | Tesla Motors
Model S Options & Pricing | Tesla Motors (may not be the same, depending on your country)
industrial.panasonic.com/www-data/pdf2/ACA4000/ACA4000CE240.pdf
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