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We use track data, charging data, and some simple math to estimate results.
Our preliminary estimate is that the Tesla Model 3 Performance, due to high battery temps, would not be able to charge at 250 kW like the Taycan at the high ambient temps encountered at the Nardo track. Also, the total miles the Model 3 could accumulate during a simulated 24-hour endurance test would be 1,930 miles versus the 2,129 miles attained by the Porsche Taycan.
In the event that we are wrong and the Model 3 Performance can charge at the V3 Supercharger rate without overheating, it would achieve the same as Taycan’s total miles.
As we mentioned, our analysis is based on data and also some simple math and modeling using our performance model and our battery cooling model. Therefore, these results are subject to many assumptions and should be considered preliminary at best. The best way to prove us wrong would be for Tesla to run the same endurance test.
For the Porsche data, we used the 24-hour endurance test (ref) in which the Taycan achieved a nearly constant 127-mph average speed over a 24-hour period at the Nardo oval track in Italy. Including charging stops, the Taycan was able to cover 2,129 miles in hot ambient conditions with peak temps as high as 40C (104F) ambient and 54C (129F) on the track. The performance model allowed us to determine the battery pack load at 127 mph. We assumed the Taycan would be charging at a nearly constant 250 kW during its approximate 12-minute charging stop.
Our Model 3 Performance estimates are based on V3 Supercharging data collected by Tesla Motors Club members Zoomit, MarcG, and others. That thread can be found here. The charging profiles we used are shown below.
Similar to our analysis of the Taycan, we used our performance model to estimate the battery loading at 127 mph for the Model 3, along with other parameters. We also used our battery cooling model to determine battery temperatures at Nardo track conditions. The model predicted no overtemp for the Porsche Taycan at track conditions.
The Porsche Taycan completed the endurance run without any noted overheating issues. However, based on our modeling of the charging profiles for the Model 3, we estimate that the Model 3 Performance would not be able to hold a 250 kW charge rate without overheating at the 104F ambient temperatures that existed at the Nardo test track during the Taycan’s run.
Looking at the Model 3 V3 Supercharging profile in figure 1 above, it was postulated in the TMC thread that the sharp cutback in charging power at 25% state of charge was due to a thermal overload of the pack.
Our battery cooling model also predicts this same thermal overheating.
Per ME systems modeling and analysis:
This may sound like a contradiction to our previous analysis where we showed that the overall thermal conductivity of the Model 3 cooling system was nearly twice as good as the Porsche/Audi flat plate cooling system. We stand by that assumption and it is still a basic part of our battery cooling model. However, the total cooling system performance is comprised of more than just the thermal conductivity.
The internal resistance of the cells also comes into play, and our research indicates that Tesla’s high energy density NCA cells have a higher internal resistance than Porsche’s NMC cells on an equivalent kWh basis. Also, couple that with the (postulated) 10% oversizing of the Porsche battery. In other words, Porsche only uses 90% of its total battery kWh’s.
So, the lower internal resistance of the cell itself PLUS an oversizing of the pack kWh’s results in lower internal resistance, and therefore, lower heat rejection from the Porsche pack. Porsche’s 2-speed gearbox probably plays a part as well. This may be why Porsche can get away with a (postulated) flat plate cooling system and why Tesla needs a robust cooling system where the cooling ribbon is glued right to the 2170 cell.
The detailed calculation sheets are included below:
Credit: Keith Ritter (HVACman) owner of ME systems engineering
This article originally appeared on Inside EVs.