Here's my efficiency vs temp chart:
May I ask how you pulled that chart? It looks like it's from Stats, but I don't see that graph anywhere ...?
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Here's my efficiency vs temp chart:
May I ask how you pulled that chart? It looks like it's from Stats, but I don't see that graph anywhere ...?
It is from Stats. In the upper right hand corner of the efficiency graph there’s a link to show it this way.
Here’s mine with a bit wider temp range:
One more point, often not well-appreciated. Average speed is not the important metric. Since wind drag is proportional to speed^3, speed excursions above the average speed have an outsized impact on energy consumption. In order to compute the relevant speed average (at highway speeds, you would technically need to take the instantaneous speed, raise to power 3, take the overall average of the "cubed speed" over the trip, then take the cube root. Technically, i suppose this would be a RMC: "root mean cubed". None but the biggest nerds would attempt this, however... Maybe if Sheldon drove an EV...You drove at:
(377rkm-179rkm *130.5Wh/rkm)/ 125km =
207Wh/km (331Wh/mi)
(224rkm-78rkm)*130.5Wh/rkm/ 97km =
196Wh/km (315Wh/mi)
That was your trip meter efficiency on the return assuming your data is good.
You used 198rkm + 146rkm = 344rkm
to travel 222km.
Means you drove a factor of 344/222 above rated efficiency of 130.5Wh/rkm (209Wh/mi)
which means you did on average:
130.5Wh/rkm*344rkm/222km = 202Wh/km
To me this seems a bit high overall for a flat drive even when running heat, at 105km/h. But it is conceivable if it was windy or rainy. I do wonder if you were careful to track all your losses when parked though.
Yes, sort of, there is very little analysis required though, see this post:
Suspicious range numbers
Feel free to post detailed trip meter data and rated miles before and after if you still have questions. It is pretty straightforward though; rated km use is completely deterministic and predictable, except in some rare special cases where something goes wrong.
If the overall picture still does not make sense with the trip data, etc., then maybe there is something wrong. But likely it will make sense if we look at the numbers.
Since wind drag is proportional to speed^3, speed excursions above the average speed have an outsized impact on energy consumption. In order to compute the relevant speed average (at highway speeds, you would technically need to take the instantaneous speed, raise to power 3, take the overall average of the "cubed speed" over the trip, then take the cube root.
Correct thatefficiency drops with v^2. Great explanation of why the math works that way.True that it is proportional to speed cubed, but you get there faster, so the energy required per mile only goes up with the square of velocity. So I think (not thinking about it too carefully) that if your objective is to figure out average Wh/mi, you should take the RMS value as the relevant value. I think. But in any case your point about excursions mattering a lot is definitely relevant even if it's "only" RMS. Of course it's only the aero loss component (which can be quite large) which is scaled by this velocity (squared).
Fully agree. Energy per unit time (power) due to drag is proportional to velocity^3. Energy per unit distance due to drag is proportional to velocity^2. So Wh/km (or Wh/mile) is proportional to velocity^2.True that it is proportional to speed cubed, but you get there faster, so the energy required per mile only goes up with the square of velocity. So I think (not thinking about it too carefully) that if your objective is to figure out average Wh/mi, you should take the RMS value as the relevant value. I think. But in any case your point about excursions mattering a lot is definitely relevant even if it's "only" RMS. Of course it's only the aero loss component (which can be quite large) which is scaled by this velocity (squared).
Thanks for the calculation. This is kind of what I'm getting at..
While there are certainly cars with range loss as referenced in these threads, the OP’s thought that the range loss is “hidden” cannot be supported with available data. Even in these threads, the vehicles with loss of range show a reduced number of available rated miles/km. It is not hidden.
The OP’s issue is (apparently) just an issue of driving above rated consumption due to whatever factors.
That is distinct from range loss. Unless Tesla is being super duper tricky and changing the trip meter Wh/mi scaling. (Which is pretty unlikely.)
Energy monitored going into charger (in between electrical outlet and Tesla charger) shows full 55 kw or whatever the battery capacity is.
If Tesla is using their estimate of the battery charge level based on V measured to determine kWh used, stored, and charged then they effectively defacto DO define what a “kWh” is. I don’t know for sure they are doing this, or if they also have a current meter built into their circuity for a sanity check, but just basing it all around battery V would be by far the easiest and would be inherently internally consistent.This is the only way to know for sure, but do you have comparative historical data?
I do not believe there is any really funny business from Tesla to mask any losses. The losses are right there, obvious to see, in the form of a reduced number of rated miles at a given %.
However, regardless of what I think, documented charging data showing exactly how many kWh it took to add a given number of rated miles, and how this changes over time, is really all that we can look at, to see if Tesla is changing the definition of kWh. I can go back to some of my Chargepoint sessions and look I suppose. Even that is tricky because I have to be sure the session had no "shore power" use where I pre-warmed my car...
6/23/2019: 100% charge (extrapolated): 310 rated miles.
Chargepoint added 32.483kWh. Stats says I added 125 rated miles, 30.68kWh (245Wh/rmi)
Efficiency: 94.4%
Today: 100% charge (extrapolated): 304 rated miles.
Chargepoint added 24.257kWh. Stats says I added 92.5 rated miles, 22.63 kWh (245Wh/rmi)
Efficiency: 93.3%
So efficiencies are very similar (note the charging station was not the same so there may be meter variation)...I could process more data for a long-term average - but no real evidence that the definition of kWh has changed at all with V10 or any other update.
It's better for someone using exactly the same meter to do this comparison.
FYI in the last week Tesla sent me a message on my app that they are refunding me about $26 in SC overcharges. I’d seen some weird, tiny credits showing up on the CC linked to my Tesla account but not yet reaching the $26 total (though I haven’t checked my CC activity in last few days).Furthermore: since Tesla charges for kWh at the Superchargers, they would likely get in trouble if they started changing their definition of what a kWh was (specifically, they would need to make it smaller if they were trying to trick us or hide loss of capacity). It probably has to be reasonably accurate to not get in trouble with the Bureau of Weights & Measures. Those kWh are shown on the charging screen and there is a direct scaling from that to trip meter kWh, and furthermore a direct relationship between that and your available battery capacity (based on your rated miles available at a full charge).
If Tesla is using their estimate of the battery charge level based on V measured to determine kWh used, stored, and charged then they effectively defacto DO define what a “kWh” is. I don’t know for sure they are doing this, or if they also have a current meter built into their circuity for a sanity check, but just basing it all around battery V would be by far the easiest and would be inherently internally consistent.
They (and someone somewhere needs to have something of a clue) aren’t telling there customers wtf is going on, why suddenly this drop that cuts so much across miles driven, build config, and age that it breaks credulity that it could actually be true physical degradation, a change in the chemical/physical state of the cells. That’s by definition “hiding something”.Tons of people are reporting rated range loss anyway, so that's also supportive of the thesis that Tesla is not actually hiding anything.
They (and someone somewhere needs to have something of a clue) aren’t telling there customers wtf is going on, why suddenly this drop that cuts so much across miles driven, build config, and age that it breaks credulity that is actually true physical degradation. That’s by definition “hiding”.
They don’t need to, they just blow it off as “no problem, normal” because the number doesn’t strictly trigger the warranty.That's true. I just meant they aren't hiding the available energy loss, specifically.
This is the only way to know for sure, but do you have comparative historical data?
I do not believe there is any really funny business from Tesla to mask any losses. The losses are right there, obvious to see, in the form of a reduced number of rated miles at a given %.
However, regardless of what I think, documented charging data showing exactly how many kWh it took to add a given number of rated miles, and how this changes over time, is really all that we can look at, to see if Tesla is changing the definition of kWh. I can go back to some of my Chargepoint sessions and look I suppose. Even that is tricky because I have to be sure the session had no "shore power" use where I pre-warmed my car...
6/23/2019: 100% charge (extrapolated): 310 rated miles.
Chargepoint added 32.483kWh. Stats says I added 125 rated miles, 30.68kWh (245Wh/rmi)
Efficiency: 94.4%
Today: 100% charge (extrapolated): 304 rated miles.
Chargepoint added 24.257kWh. Stats says I added 92.5 rated miles, 22.63 kWh (245Wh/rmi)
Efficiency: 93.3%
So efficiencies are very similar (note the charging station was not the same so there may be meter variation)...I could process more data for a long-term average - but no real evidence that the definition of kWh has changed at all with V10 or any other update.
It's better for someone using exactly the same meter to do this comparison.
Furthermore: since Tesla charges for kWh at the Superchargers, they would likely get in trouble if they started changing their definition of what a kWh was (specifically, they would need to make it smaller if they were trying to trick us or hide loss of capacity). It probably has to be reasonably accurate to not get in trouble with the Bureau of Weights & Measures. Those kWh are shown on the charging screen and there is a direct scaling from that to trip meter kWh, and furthermore a direct relationship between that and your available battery capacity (based on your rated miles available at a full charge).
Can you tell just by calculating energy going into the charger and the on screen Tesla numbers? How much of that was diverted to other car processes in disguise?