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Actual rated wh/mi
- Thread starter Teefal
- Start date
Also, teslafi has a preference ...
Three Phase Correction:
If the kWh used is incorrect on home charges using three phase you can select to correct the calculation and enter a factor to adjust it.
It's currently 1.0. If I wanted to eliminate the B-S and have yesterday's drive be 100%, what's the factor?
Three Phase Correction:
If the kWh used is incorrect on home charges using three phase you can select to correct the calculation and enter a factor to adjust it.
It's currently 1.0. If I wanted to eliminate the B-S and have yesterday's drive be 100%, what's the factor?
So you're saying the 280 Wh/mi number and the 316 number are not related to each other, from an EPA standpoint.
This is my car, and the answer. Last night I looked at the energy consumption graph and guesstimated exactly 246 Wh/mi rated. First graph shows dotted line above solid line. Next chart shows dotted line on top of solid line, and the number is 246.
TomServo
Active Member
Fascinating discussion. With all these numbers being bantered about and all could be considered correct or incorrect based on your point of view, I can see why EV buyers are confused. An example is how Ford rated the MME for 270 miles and many new owners report they get 270 at freeway speeds, yet Tesla rates the Y at 326 miles and on a good day might get close to 260 miles at freeway speeds (all else being equal). So in that context, it appears Ford is more HONEST and Tesla is LESS HONEST in their ratings (GOOD PR vs BAD PR) but many never mention the huge difference in battery capacity, all that matters is Ford is MORE honest.
All I know is if I drive and get the dotted line to merge with the solid RATED line in the Energy app, it display 245 to 247 wh/mi. To maintain that and get the EPA RATED 316 miles I'd need to maintain about 50 mph. Not very practical.
But here in "flatland" USA (southern IL) I average about 280 to 290 wh/mi at "freeway speeds with the HVAC set to AUTO and 72 degrees and tires pumped up to 44 PSI COLD. Any other conditions and all best are off.
All I know is if I drive and get the dotted line to merge with the solid RATED line in the Energy app, it display 245 to 247 wh/mi. To maintain that and get the EPA RATED 316 miles I'd need to maintain about 50 mph. Not very practical.
But here in "flatland" USA (southern IL) I average about 280 to 290 wh/mi at "freeway speeds with the HVAC set to AUTO and 72 degrees and tires pumped up to 44 PSI COLD. Any other conditions and all best are off.
Can't speak to "honesty", but personally I'm fine with 200 miles between supercharging. It matches with when I want a break and usually takes 20-30 minutes, which is enough of a break.
That 200 is the magic number between 85% SOC and 20% SOC (in practice). Gives me a 20% buffer and doesn't overcharge so the battery stays healthy.
I just wanted to know what the solid line meant
That 200 is the magic number between 85% SOC and 20% SOC (in practice). Gives me a 20% buffer and doesn't overcharge so the battery stays healthy.
I just wanted to know what the solid line meant
AlanSubie4Life
Efficiency Obsessed Member
The EPA numbers are wall-to-wheel and include charging losses. It will never match the rated line in the car.Getting closer, I think
Wouldn't that mean the battery needed to hold 88.4 kWh?
What TeslaFi calculates as efficiency I am not sure but you could work it out and they probably have a FAQ.
If you have questions about the rated line and constant you can provide a picture of the energy screen (in distance display mode) and then I can calculate it for your particular Model Y, and explain your results. You don’t have to “drive to the line” or anything like that. Just the picture with the three key numbers (rated remaining, projected range, and recent AVG efficiency).
It is all 100% deterministic, pretty much. No mysteries here. Just have to know the base numbers and do the math. But it takes some basic knowledge of how it works to calculate. Happy to do it with a well documented example from you.
AlanSubie4Life
Efficiency Obsessed Member
Catching up on posts. So likely this means the actual rated constant used by the car is about 240Wh/mi (5Wh/mi lower). If you take another picture and include your rated miles at the same time that can be determined with certainty.
For whatever reason the line position is 5Wh/mi higher than the charge constant, at least on Model 3. A picture from Model Y would confirm that though I expect it behaves the same.
So this means you need to drive at 95.5% of that, or ~230Wh/mi, for parity, mile-for-mile rolloff. However, please do not take this number as a given. Need more info to be sure the number is correct.
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whisperingshad
Active Member
FloridaSun
Member
Tried to drive with a light foot, no AC (in 90 degree weather) and minimal use of autopilot around town and averaged 195 Wh/mile. That's 5.13 mi/kwh which is very good.. I'll get the front windows tinted and the sunshade to see if I can reduce consumption from the AC that way..
AlanSubie4Life
Efficiency Obsessed Member
Just another note for the Model Y Non-Performance: It has a 77.8kWh battery when new (about- need SMT capture to make sure this value is exactly correct; I am using Model 3 value). From the capture above (195*260/0.64 = 79kWh) it looks like for Model Y it might be 79kWh - there is some flexibility on this from Tesla. And this could be as low as 78.6kWh. I'll just use that number here but more precision is needed.
So the constant is likely 78.6kWh/326mi = ~241Wh/mi. (So matches the 240Wh/mi number above, about 5Wh/mi lower than the rated line as expected.)
So your max available energy going forward is your (Rated Miles @ 100%) * ~241Wh/mi (So this will go down with time as you lose rated miles.)
This number when new is 78.6kWh, but the Model Y (I think) has a 4.5% buffer like the Model 3 (needs confirmation of the % but let's assume so).
So only 95.5% of it is available from max rated miles to 0 rated miles. So that would be: 75kWh.
So that's why you end up with 75kWh/326mi = ~230Wh/mi for parity (I said 230Wh/mi above).
In reality due to "heat losses and missing energy" from the trip meter, you probably need to get about 99% of this, or 227Wh/mi.
So you can just drive around and confirm this - just do the math. Just remember that the trip meter does not count energy use while in Park. So if you're doing any experiment you need to be careful.
It's great because there's really no guessing about how much energy you have at any time. How you use it is up to you.
And it all aligns with the EPA numbers, which should reflect about 88.5% charging efficiency (270Wh/mi or so).
I'm using the 2021 numbers here (326 miles rather than 315 miles). However, if 2020 vehicles received a range increase they'd all be the same constant (I don't keep track of this for Model Y). It's just a different constant and doesn't really change anything. (But would explain the 270Wh/mi vs. 279Wh/mi EPA numbers or whatever the difference is - I haven't checked the EPA data for Model Y.).
Anyway it's all knowable, there's very little ambiguity. Just look at the energy screen and it will tell you everything you need to know about your approximate battery capacity, charging constant, etc.
So the constant is likely 78.6kWh/326mi = ~241Wh/mi. (So matches the 240Wh/mi number above, about 5Wh/mi lower than the rated line as expected.)
So your max available energy going forward is your (Rated Miles @ 100%) * ~241Wh/mi (So this will go down with time as you lose rated miles.)
This number when new is 78.6kWh, but the Model Y (I think) has a 4.5% buffer like the Model 3 (needs confirmation of the % but let's assume so).
So only 95.5% of it is available from max rated miles to 0 rated miles. So that would be: 75kWh.
So that's why you end up with 75kWh/326mi = ~230Wh/mi for parity (I said 230Wh/mi above).
In reality due to "heat losses and missing energy" from the trip meter, you probably need to get about 99% of this, or 227Wh/mi.
So you can just drive around and confirm this - just do the math. Just remember that the trip meter does not count energy use while in Park. So if you're doing any experiment you need to be careful.
It's great because there's really no guessing about how much energy you have at any time. How you use it is up to you.
And it all aligns with the EPA numbers, which should reflect about 88.5% charging efficiency (270Wh/mi or so).
I'm using the 2021 numbers here (326 miles rather than 315 miles). However, if 2020 vehicles received a range increase they'd all be the same constant (I don't keep track of this for Model Y). It's just a different constant and doesn't really change anything. (But would explain the 270Wh/mi vs. 279Wh/mi EPA numbers or whatever the difference is - I haven't checked the EPA data for Model Y.).
Anyway it's all knowable, there's very little ambiguity. Just look at the energy screen and it will tell you everything you need to know about your approximate battery capacity, charging constant, etc.
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FloridaSun
Member
I did a little research on the subject and I can't figure out how the Model Y got the 326 mile range??? The EPA efficiency rating for the Model Y is 125 mpge combined, highway and city. 125 mpge translates to 3.71 miles/kwh. Now, if I multiply 3.71 with the battery size (about 78 kwh useable space), I'm only getting 289 mile range??? Where am I going wrong here? How is the 326 mile range determined??
This is definitely a rabbit hole. Here is a starter: The Secret Adjustment Factor Tesla Uses to Get Its Big EPA Range Numbers
The EPA understands that their range test results in no way correlate to real world driving. The EPA applies a 30% reduction to the Dyno range test result however manufacturers are permitted to further tweak the adjustment factor by providing additional test data. (Tesla did this with the Performance Model Y and applies a 24.4% reduction factor instead of the standard 30% range reduction factor.)
Also, Tesla's vehicles tend to have more reserve range when displaying 0 miles than other EVs. Tesla saves more range at 0% than other EVs, test finds
The EPA understands that their range test results in no way correlate to real world driving. The EPA applies a 30% reduction to the Dyno range test result however manufacturers are permitted to further tweak the adjustment factor by providing additional test data. (Tesla did this with the Performance Model Y and applies a 24.4% reduction factor instead of the standard 30% range reduction factor.)
Also, Tesla's vehicles tend to have more reserve range when displaying 0 miles than other EVs. Tesla saves more range at 0% than other EVs, test finds
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Here is the data that Tesla submitted to the EPA for the Long Range Model Y, Performance Model Y. https://iaspub.epa.gov/otaqpub/display_file.jsp?docid=49398&flag=1
This thread shows the relative efficiency of the Model Y when fitted with the 19" Gemini wheels/tires; 20" Induction wheels and 21" Uberturbine wheels.
Range loss with the different wheel options
This thread shows the relative efficiency of the Model Y when fitted with the 19" Gemini wheels/tires; 20" Induction wheels and 21" Uberturbine wheels.
Range loss with the different wheel options
AlanSubie4Life
Efficiency Obsessed Member
Charging losses. It's explained above. 1/3.71mi/kWh = 269.5Wh/mi. That's 269Wh/mi (AC) *0.885 = 238.5Wh (DC) /mi
77.8kWh/238.5Wh/mi = 326 miles
The charging losses are clearly provided in the EPA document provided by @jcanoe above. Just look at the AC recharge relative to the discharge energy measured. It's always around that 88.5% - except for the 2021 Model 3 Performance for some reason which is way off. (It varies a little from vehicle to vehicle.)
That's the simple explanation - there are pesky little details but mostly they don't matter. In the end, the equation above is where the range comes from. To be precise, it's actually not calculated exactly that way above - instead, they do the 55/45% weighting of city and highway ranges and scale by the 0.756 factor (I don't know what exactly it is for the LR Model Y - but it's close - and you can get it from the EPA documents - specifically the EPA datafile implicitly provides it). That gives you the range. And then for the AC efficiency they take the AC recharge energy and divide by that range. But it ends up being equivalent - just details of the derivation and basically by starting from the MGPe rating you're working backwards.
The scaling factor is based on the results of the 5-cycle tests (via a HIGHLY inscrutable formula which I haven't ever dug into to see if I can calculate the scalar), so the two-cycle rating is actually implicitly including all 5-cycles, since Tesla chooses not to use the 0.7 factor like most other manufacturers currently do.
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FloridaSun
Member
Interesting.. I never knew that charging losses are part of the calculation as they vary based on what kind of charger you are using.. Level 2 losses are different from DC Fast or Supercharging losses.. Tesla losses may be higher compared to other brands when fast charging as Teslas pre-heat the battery which also uses energy.. So, with a battery fully charged at about 78kw, the car would need to average 4.2 miles/kwh to achieve rated range. I would say that this is very possible with the AC being OFF unless of course the car is tested in a moderate climate. Here in Florida, you can't even come close to rated range in summer but the good thing is that we don't need the heater in winter, so efficiency in winter is pretty good even though when the battery is cold, it will also affect range.
AlanSubie4Life
Efficiency Obsessed Member
Yeah, if you look at the charge time above in the link provided, it looks like they might have been using 11.5kW (48A) charging, since the average charge wattage was 11kW (took 8 hours). That's actually surprising to me (I think using 32A would be more fair since that is the equipment provided), though it does make their numbers look the best. It's actually the first time I've seen this info in the EPA document and it's good to see that they are using 11.5kW charging to get ~87% efficiency (in that case).
Yes, they're different for DC chargers (the conversion losses are on the charger side, not the car side, and the much higher currents lead to a different distribution of losses). In the end you still pay for them, in the rate charged, though. (If they didn't exist the cost would be lower.)
Yes, you'd need to do about 1/4.2mi/kWh = 239Wh/mi (indicated as 236Wh/mi on the trip meter) AND ( this is key) you'd need to drive all the way through the 4.5% buffer below 0, until the car stops dead on the road and shuts down. If you only want to drive to 0%, then you need to do 228Wh/mi (indicated as 225Wh/mi) to get the rated range. 4.5% lower since there's 4.5% less energy to work with.
Your line on your energy screen is likely right around 244Wh/mi or so (5Wh/mi higher than 239Wh/mi). What the exact value is depends on whether 77.8kWh is the right value, or Tesla is using something slightly different. But it's right in the ballpark.
FloridaSun
Member
Isn't the buffer the 4.2 kwh between 77.8 and 82kwh or is there an additional bottom end buffer? I assume that the extra 4.2kwh are top end buffer..
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