I'm afraid I don't understand that. I did digital signal processing for 40 years and that doesn't tell me anything I can comprehend in terms of that experience. Could you expand on that thought a bit?. Are you saying that this is aliasing error?
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Wh / Mile vs Actual electricity draw 50% discrepancy
- Thread starter muncheroo
- Start date
Another question: when you are at a Supercharger does Tesla charge you for energy put in the battery or the actual electrical consumption on the grid?
I have free supercharging so I never see a bill and an account of that. However the app "STAT" only seem to count the KWH taken in by the battery.
I would assume a 10% or so difference?
I think they are charging for what you take in and I imagine the cost of what they pay the utility is factored into the price. It wouldn't be very fair to charge you extra because one or more of their rectifier modules becomes less effective or because they are saturating a transformer due to heavy load.
Also I think you are probably right about the efficiency being approximately 90%. The superchargers use arrays of the chargers they build for vehicles (at least they used to) and those run about 90% efficient. Plus this is around state of the art.
BTW, even though you are getting free charging the display in your car still shows what the cost of the charge is. But you never get billed and after disconnecting the cost field resets to $0.00.
Also I think you are probably right about the efficiency being approximately 90%. The superchargers use arrays of the chargers they build for vehicles (at least they used to) and those run about 90% efficient. Plus this is around state of the art.
BTW, even though you are getting free charging the display in your car still shows what the cost of the charge is. But you never get billed and after disconnecting the cost field resets to $0.00.
DC supercharging is probably very efficient as compared to L1/L2 as it does not involve converting AC to DC
never seen that $$ display on my X
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The Grid is AC so it needs to be converted, but that conversion is pretty efficient.
If you are driving 1/3 of a mile but the trip meter takes a sample for distance only every 0.2 miles and energy only every 20 seconds (I don't know the exact numbers but looking how the numbers update that's my estimate) then you are getting useless 'averages' if you look at it after 1/3 of a mile. Does that make sense?
From the POV of the car it is. Over 99%. From the POV of the SC it isn't as it has to sustain the losses of the transformer that feeds the rectifier modules and the losses of the rectifier modules themselves. OP opined that those losses were probably about 10% and as the losses of the rectifier modules are about 10% I think he's probably right.
It's in the loer RH corner of the charging window. First time I used an SC I was horrified to see the $ mounting up during the charge as I had been promised free supercharging for 6 months. When I got home I noted that the name of the SC I had visited was still on the display but that the charges were listed as $0.00.
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It would if those were the numbers but it is clear that the car updates the displays (graph and trip meters) every tenth of a mile and I would expect that it samples more often than that. Note that I reported the car went a couple of hundred feet and that the trip meters updated. A tenth of a (statute) mile is 528 feet and 200 - 300 feet is less than that. Thus it appears that dist mod 0.1 was equal to about 0.05 when I started off and after another 0.05 mile the distance was an integral number of tenth mile so the display updated.
By recording the numbers on the "Since hh:mm" display you can get the wHr recorded at each 0.1 mile. From that data it is clear that a lot more energy is being used in the first tenth mile. The plot below shows what the screen graph would show when data from a recent drive is smoothed by a half mile window (red - this is clearly what the 5 mi resolution display uses and by a 1 mile window (blue - the 15 and 30 mile displays clearly use a longer window but I can't tell how long or whether it is the same for 30 and 15).
Note that the vertical axis should be labeled watt hours per mile and that distance driven increases towards the right (opposite of the way it is in the car). The smoothed spike from the departure tax is clearly visible especially in the higher resolution window. There is something causing the first 10th of a mile to register consumption that is substantially greater than the consumption normally associated with the gradual acceleration and low speed associated with going down my driveway and getting onto the local road which is 200 - 400 Wh/mi as opposed to the 800 indicated by the graph. The earliest part or the trip shows energy demand more like that where I goosed it going up hill at around 3 miles. As I can think of no other sink for that energy I have assumed it is the energy used to warm the car prior to my departure.
Evidently some here feel pretty passionately that this is wrong. I welcome any altrernative explanation as to where this energy drain came from. I just want to get to the bottom this. Until one comes along I am forced to assume that this energy was used to warm the car while it was parked.
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I know but my X shows in that field when I am plugged in at SC (Current Session):
No Recent Supercharging
Note I have Unlimited Free Supercharging
Sorry to barge in here, but it sounds like you can clarify something for me. I assumed that it was not calculating when the car was in "Car Off" state, but was calculating while in Park. This assumption is based on the fact that the " Since hh:mm" trip meter starts when you switch from Car Off to PRND whether you shift out of Park or not. Do your CAN readings directly contradict that?
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I just tested this. The car will not count energy when in P. If you are in D, it will count energy but only update after you start driving again. So when you get in the car, put it in D but don't start driving right away, the energy will be counted but will cause a spike in 'consumption' once you start driving.
If I put the car outside in park with the doors open on a cold day, jump in shut the doors, put on my seatbelt, wait for the seat to position, turn the heat down, pop it into D and drive off immediately there is a huge spike as soon as enough distance has been accumulated to get the OD to tick up to the next tenth mile (this can be appreciably less than 0.1 mile depending on what the OD read when you stopped last). How do we explain that? When was that energy accumulated?
Thanks for this. I know it also measures in N while driving, so I'm guessing it measures in R, and I'm guessing it measures in all of those while at a standstill as well. Personally, I'm glad it doesn't measure in P, because there is no way to quickly switch to "Car Off" without getting out of the car.
Let's assume your "huge spike" may be 1200Wh/mi vs a highway average of 337.5WH/mi (July2017+ X100D).
337.5/1200=.28
Let's assume you have an ICE vehicle with a 2008+ EPA highway rating of 28 MPG.
28*.28=7.84
How would YOU explain it when you get in that ICE, reset the fuel economy meter, start the car, and immediately start driving it the exact same way you would drive the X100D only to see an average MPG reading of 2 - 8?
I'd recommend using the exact same explanation to cover what you're seeing in the X100D.
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Never seen $$ on my FUSC Model 3 either.
But I will soon now that I canceled it for $5k
You’re still using a ton of heat in those first few miles, warming up stiff tires, softening up grease in bearings, oil in motors. A cold vehicle is harder to push, regardless of how much you preheat cabin.
First couple readings might not be super accurate either.
I bet if you got in and going quickly the numbers wouldn’t be that different. Or if you let it pre heat for 20 minutes you see 20,000 wh/mi if the meter was running while parked according to your logic. Meter is not running. It is running if it’s in Drive though.
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