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Adding on to this... if the above pack sizes are in the ballpark, supercharging rates are interesting.
For the large pack, Tesla advertises adding 170 miles or range in 30 mins. That's 55% in 30 mins.
Allowing for the bottom buffer (I suspect that's the right way to figure this, as the 0-100% range excludes the buffer), that's 55% of 73.5KWh or 40.4KWh of energy. That's an average rate of 81KW for the first half hour, or a roughly a 1.08C rate.
The standard range Model 3 adds 220/130= 59% range in 30 mins. Assuming the 52.1 KWh pack, that's 30.7KWh, or an average power of 61.4KW. That's a 1.14C rate.
As a comparison, here's a graph (perhaps an early one) for Model S:
Without grid lines, I'm estimating a bit, but it would appear that the first 30 minutes start at a bit less than 120 and end just above 60KW. The median would be about 90. Given the first part of the graph holds reasonably flat for the first ~10 minutes, I'd guess the overall average is closer to 95KW or a 1.12C rate.
Not really all that much of a difference. Without a graph, it's hard to know what the max C-rate would be, but if the average for the first 30 mins is around 1.1, it's not hard to imagine that the peaks could be near the same 1.5-1.7 that the Model S's do...
For the large pack, Tesla advertises adding 170 miles or range in 30 mins. That's 55% in 30 mins.
Allowing for the bottom buffer (I suspect that's the right way to figure this, as the 0-100% range excludes the buffer), that's 55% of 73.5KWh or 40.4KWh of energy. That's an average rate of 81KW for the first half hour, or a roughly a 1.08C rate.
The standard range Model 3 adds 220/130= 59% range in 30 mins. Assuming the 52.1 KWh pack, that's 30.7KWh, or an average power of 61.4KW. That's a 1.14C rate.
As a comparison, here's a graph (perhaps an early one) for Model S:
Without grid lines, I'm estimating a bit, but it would appear that the first 30 minutes start at a bit less than 120 and end just above 60KW. The median would be about 90. Given the first part of the graph holds reasonably flat for the first ~10 minutes, I'd guess the overall average is closer to 95KW or a 1.12C rate.
Not really all that much of a difference. Without a graph, it's hard to know what the max C-rate would be, but if the average for the first 30 mins is around 1.1, it's not hard to imagine that the peaks could be near the same 1.5-1.7 that the Model S's do...
Since I have been estimating 1C charge rates, I like your data better ;-)
Can you think of a reason why the larger pack would have a lesser C rate ?
One other point: Should't the C rate be based on nominal capacity rather than usable ?
The larger pack could possibly be current limited by the supercharger and/or the port/cabling. The Model S 70KWh packs actually can hit 1.7C for a peak, which seems to be the max the system can deliver (it appears that a current limit of ~365A is reached for a brief period). The same could be happening here. But the difference between the two is pretty slight, so if so I suspect it's a small portion of the charging curve.
As for C-rate, manufactures base that on the labeled capacity of the cells. Tesla chooses a suitable bottom buffer for the pack for longevity's sake, so the 0-100% range scale needs to be baed on that , but the actual power delivery rate should be compared to the overall pack capacity, IMO.
Certainly not gospel. Good enough for spit-balling, however.
And it also provides some context that that, in the overall ballpark, the Model 3 supercharging is not likely the large disappointment that some have made it out to be.
Looks like Model 3 LR gets 126 MPGe, which is 267.5 Wh/mi wall-to-wheel efficiency
From: Fotos und Details von der ersten Tesla Model 3 Auslieferung - ecar-rent.com
From: Fotos und Details von der ersten Tesla Model 3 Auslieferung - ecar-rent.com
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Starting from 126 MPGe for the EPA combined cycle for the 310 mile Model 3,
this works out to a 82 kWh usable capacity pack.
Seems too high a result. Am I doing something wrong here ?
this works out to a 82 kWh usable capacity pack.
Seems too high a result. Am I doing something wrong here ?
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JeffK
Well-Known Member
The result you might be seeing is that MPGe is a worthless measure
That I know; it just forces me to calculate backwards for a Wh/mile result I can actually use.The result you might be seeing is that MPGe is a worthless measure
To the extent that range is ~ proportional to battery size in the Model 3,
the Base 220 mile Model 3 then works out 82*(220/330) = 58 kWh usable.
These battery pack numbers just seem too high.
Yes, you're not subtracting the charging losses. EPA MPGe data is wall-to-wheel. The EPA range data is battery-to-wheel.
Assuming ~90% charger efficiency, that equates to ~75 kWh usable
All MPGe does is confuse the average person into thinking that EVs are actually hybrids that use gasoline.
I disagree.
MPGe allows people to compare the efficiency of gas and electric cars using a measuring stick most people are familiar with.
If you can come up with a better term, by all means send the suggestion to the EPA.
I think it serves it's purpose very well.
JeffK
Well-Known Member
Miles per kWh or kWh per mile are great ones for starters.
126 MPGe equals 3,74 miles per kWh or 3,74 MPkWh
It also equal 267 Wh per mile or 256 WhPM
One uses money to pay for those gallons and those kWhs.
What it all boils down to is miles per dollar.
It also equal 267 Wh per mile or 256 WhPM
It is useful in countries where 1kWh costs the same as 1 gallon.
One uses money to pay for those gallons and those kWhs.
What it all boils down to is miles per dollar.
I don't think that is right.
The problem appears to be that the range estimate is derived from a complex weighted average of the city and highway tests. From TorqueNews (my bolding):
While the MPGe uses a different weighting of 0.55 city and 0.45 highway
This really comes down to not being able to accurately derive battery usable capacity from EPA data until the actual city and highway MPGe are known; and even then the calc will be an estimate because of the variable constant speed driving in the range test. Voodoo.
I wonder if the EPA publishes the energy required to replete the pack at the end of the range test. THAT would be informative.
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