Wh / Mile vs Actual electricity draw 50% discrepancy

[mswlogo]

Wh/mi is just a guide tool. It does not need to be absolute. But if for a long trip if my mine is reading lower than yours I’m using less power.

You do need to be careful because it uses voltage to judge capacity.

My personal belief is the meter covers everything when the car is in drive. If it’s in park it does not.

You can kind of tell from the automatic trip meter. As soon as you put it in drive it resets. But if you only put it back in park and then back to drive it does not reset ( still running ). It has a timeout of how long you need to be in park before it resets next when you put it in drive.

If you want to take HVAC out of the equation. Turn it OFF

 

[ajdelange]

Wh/mi is just a guide tool. It does not need to be absolute.

Because this is such an important point I'll reiterate: at any point in a drive it is a better estimator of remaining range or SoC at destination than any other number because it reflects the way you have been driving and the conditions you have been driving in. But is is still only a predictor which cannot account for unpredictable things further along the route.

You do need to be careful because it uses voltage to judge capacity.

Can you amplify on that? Given that the voltage of lithium batteries does not change much with SoC (except near the full and empty points) it is not a good predictor of SoC. OTOH lithium batteries are very coulomb efficient meaning that a coulomb put in can eventually be withdrawn. Given this the way to determine SoC is to account for every coulomnb (1 ampere second) that flows into or out of the battery. Thus one knows, at any given time, how many ampere hours are in the battery. One could, thus, report SoC in percent, as the number of ampere hours in the battery divided by its capacity (in ampere hours). But energy is a different matter. Power is the product of current and voltage and the energy in the battery would be the product of the voltage and current to discharge taking into account the decrease in voltage as the battery discharges. Tesla claims the BMS is extremely sophisticated and I don't doubt that but I don't know whether the SoC% number represents % of full capacity in ampere hours or % of full capacity in kWhrs. I suspect it's the latter as you have the option of displaying it in miles and it takes watts, not amps, to move the car.

My personal belief is the meter covers everything when the car is in drive.

Not much question there.

If it’s in park it does not.

I don't know enough yet to form the basis of a belief. Years of experience have me trained to base beliefs on evidence. The evidence seems to suggest that it does but I don't have enough to support belief yet.

If you want to take HVAC out of the equation. Turn it OFF

What I'm really trying to find out is if the departure tax imposed by running HVAC prior to departure is accounted for in the trip. It should, of course, be (at least I think it should). But is it?

 

[gnuarm]

We may, for whatever reason care about overall efficiency, but in terms of trip planning and progress monitoring (the subject of this thread) we don't care a whit about charger losses, transmission line losses, transformer losses, heat lost at the power plant etc. What we care about is what's in the battery, however it got in there, and the rate at which we will be pulling it out. From this we can get a rough idea as to how far we can go or, more practically, whether remaining range at our planned destination is within out comfort zone.

Why would the manufacturer put displays in the car intended to deceive us? In fact the displays are well thought out and extremely useful. This forum abounds with advice on how to extract useful information from them but you have to know how to interpret them. I'm catching on fast but then I've had 40 years experience working with similar displays and they are pretty much second nature to me. My wife, however, wouldn't have a clue as to what any of them could tell her.

The displayed Wh/mi are not a lie. They represent, at any point in time, the Wh drawn from the battery (simple numerical integral of battery voltage times battery current) divided by the miles driven since the counter was started. These numbers are used to predict range or margin.

You yourself have tried to understand the anomalies in the data. Others have pointed out that the numbers shown do not take into account energy usage when the car isn't moving. In fact, it is hard to be sure just what the car is taking into account. While I don't need to know the losses involved in charging, the car does not accurately take into account all the obvious factors in predicting range. Otherwise I wouldn't see such wide variations in the estimated reserve on reaching a destination or charger. I've been told many times this is the only indication of range I should trust. Unfortunately I can't even trust that.

Because they are based on the driving conditions experienced on the current trip they are better numbers to use in computing destination estimates than the fixed rated Wh/mi number especially as the planners can take into account terrain. But they cannot take into account (until you actually do it) your decision to increase or decrease speed or a change in weather. These numbers are estimates. That word has, to those familiar with estimation theory, many implications attached to it. I wouldn't expect most drivers of these cars to know anything about that sort of thing and so they would rely on their experiences with the trip planners and in car displays to reach a decision as to how "accurate" their estimates are. Many who post here seem to think they are pretty reliable. Tesla seems to have done a good job. Perhaps you haven't done that checking and are thus not aware of this.

Or maybe he can do some useful things.

Evidently it does. Yesterday morning the display showed 900 Whr/mi going down my 0.1 mi driveway at 10 mph. Thus I used 90 Whr. At 15 mpH it would have taken me 24 seconds to do that (0.00666 hour) so the average power consumption would have been 13.5 kW. Sounds about right - there was perhaps an inch of snow - and the car wasn't pre-heated. When I experiment with preheating off the charger my more typical reading at the end of the drive way is 1500 and in one case 7000. These imply power consumptions of from 22.5 to 105 kW. This would either have to be sustained down the whole drieveway or more likely, peak at some point as I accelerated and then decline. Believe me, if the power meter were reading this high in my driveway I would have noticed it. The obvious conclusion is that energy used prior to departure is considered in the first reported consumption number. Common sense says that it should be but many here, such as you, assure me that it isn't. My conclusions are based on observed numbers. I find it interesting that those who disagree never offer numbers to support their position.

I've seen people who dispute your analysis refer to the numbers they read from the car's CAN bus which is a real time indication of everything going on in the car. The fact that you can't explain your readings any other way doesn't mean it proves your rationale.

 

[ajdelange]

You yourself have tried to understand the anomalies in the data. Others have pointed out that the numbers shown do not take into account energy usage when the car isn't moving.

Given the controversy on this subject I am not ready to make an assertion but the evidence keeps mounting. Two runs today confirm that the trip display does indeed include power consumed when the car is in park. I sat in the driveway for about 6 minutes in park with the heater on and set high enough that the power display was off the pin. According to logged ABRP data I should use 45 - 55 wHr in going down my 0.1 mi driveway at 10 - 15 mph. According to the trip meter I used 267. Later at Home Despot I just got in the car and the heater, of course came right on but I didn't sit there more than a minute or two. To go the first 0.1 mile into the street I should have used, per ABRP data, perhaps 40 wHr. I used 188 per the trip meter. Both trips showed energy consumed in park and the energy was proportional to the time the heater was on in park.[/QUOTE]

In fact, it is hard to be sure just what the car is taking into account. While I don't need to know the losses involved in charging, the car does not accurately take into account all the obvious factors in predicting range.

It seems to take into account the factors that it can such as battery drain rates, temperature and elevation. Those it can get data on from its own measurements and it can get terrain and forecast temperature data from the web. It cannot get meaningful forecast data on head wind component which is no doubt the biggest factor in realized range. It cannot get data on whether there will be a traffic jam when you get to a position 100 miles from where you are nor can it determine whether you will decide to go 10 mpH faster at some point because traffic is lighter than you expected it to be.

Otherwise I wouldn't see such wide variations in the estimated reserve on reaching a destination or charger. I've been told many times this is the only indication of range I should trust. Unfortunately I can't even trust that.

The reason you are seeing more variation than you would like is because it's impossible: there are very sigtnificant factors the prediction algorithm can't get data on. None the less it is the best estimate you have available to you (unless you are using another estimator that has access tothe car's data). No, you can't trust the estimate to be accurate. Don't know if you have any experience in aviation but I think even in dealing with passengers the airlines refer to the ETA. That stands for Estimated Time of Arrival. It is not offered as information about when the plane will arrive. It is an estimate of the time the plane will arrive. The airlines have excellent models of the aircraft dynamics and real time data on weather (including head winds). Even so they give you no better than an ETA because even their fancy algorithms can forecast unpredictable events.

There is a large body of art (based on science and math) that goes with these projection algorithms. Were you familiar with any of that you probably wouldn't be so uncomfortable. Apparently many users find the projections quite accurate. Perhaps they have more realistic expectations or a better understanding of the underlying principles. You should gain some perspective over time.

I've seen people who dispute your analysis refer to the numbers they read from the car's CAN bus which is a real time indication of everything going on in the car. The fact that you can't explain your readings any other way doesn't mean it proves your rationale.

Well, energy is conserved. Until someone tells me what the algorithm driving the display is I cannot with 100% certainty say what it is. I can only look at data, based on my observations formulate a hypothesis and then test that hypothesis by getting additional data from the car. Occam's razor is an obvious place to start. From it I have the hypothesis, and am collecting more drives. So far I haven't found anything that contradicts the hypothesis. I keep asking the question "If the extra energy use I see recorded in the first tenth mile isn't the energy I used before I started driving, what it it? No one has answered this (reasonably). The guy that says he has CAN bus data hasn't said: "here are some CAN bus data plots that refute your hypothesis". He's said, in essence "I've see CAN bus data and you are wrong".

If you, or anyone else thinks the hypothesis is wrong (and I am not saying that it is right - only that it seems more and more likely than the null hypothesis as I analyze more trips) then go out and do some experiments like the ones I have done. Getting more data from more drivers will help to resolve this. Just go down your driveway slowly, keep an eye on the power meter, and read the trip meter at the first tenth. Note what you did before you took off.

 

[David99]

My personal belief is the meter covers everything when the car is in drive. If it’s in park it does not.

Your belief is correct. I have tested this extensively. The trip meter will count all energy used as long as you keep the car in drive. If you stop, the trip meter will stop updating. It will count but not show it. This can give the impression that it's not counting. Once you continue to drive, the energy will update and, depending on how much energy was used during the stop, jump up.

When the car is in P none of the trip meter will update nor count, though. The trip meter especially becomes inaccurate if you use the AC or heater while the car is parked.

 

[ajdelange]

I just did two more drives today in which the trip meter did register the energy used in park, Same behaviour that I have witnessed about a dozen times now, Put the car in park. Turn on the heat and play the radio and sit there for a few minutes. Take off down the driveway and record the reading at the first update (tenth mile). Today's display was 1992 Whr/mi. For 0.1 mi that is 199 Whr. At driveway speed the car requires perhaps 450 Whr/mi to move it. For the tenth mile the power required would be 45 Whr. That leaves 154 Whr registered by the meter that you all say cannot be power consumed by the car while I was sitting there. That just doesn't make sense. Energy is conserved. If the 1992 Whr/mi reported for that first tenth does not include any of the energy used in park it would have to be used to move the car. It does not take, under any reasonable set of conditions, 199 Whr/mi to move an X a tenth of a mile. 199 Whr expended over 1/120th of an hour means average,over the whole 30 seconds, power of 24 kW. The power meter never peaks this high let alone stays this high for the whole tenth mile run.

I keep posting data that makes it pretty clear that power consumed in park is accounted for and displayed. Could someone post some data that indicates that it isn't? I'd like to understand this. David99 reports that he has tested this extensively, Could you please post some of your please post some of your test data so I can compare it to what I am seeing.

While sitting in the car with the heater on and radio playing this morning I asked the navigation system to plan a trip to a SC some distance away. The energy display in trip mode showed that I would arrive there with 44% left in the battery. After some time the indicated reserve dropped to 43%. In the other mode the display indicated that I had 273 miles range left in the battery. After sitting there with the heater on and the radio playing for some time the indicated remaining range dropped to 272 miles and after another approximately equal interval it dropped again to 271. This I also take as a pretty solid indication that the displays are accounting for energy used when the car is in park.

 

[mswlogo]

I just did two more drives today in which the trip meter did register the energy used in park, Same behaviour that I have witnessed about a dozen times now, Put the car in park. Turn on the heat and play the radio and sit there for a few minutes. Take off down the driveway and record the reading at the first update (tenth mile). Today's display was 1992 Whr/mi. For 0.1 mi that is 199 Whr. At driveway speed the car requires perhaps 450 Whr/mi to move it. For the tenth mile the power required would be 45 Whr. That leaves 154 Whr registered by the meter that you all say cannot be power consumed by the car while I was sitting there. That just doesn't make sense. Energy is conserved. If the 1992 Whr/mi reported for that first tenth does not include any of the energy used in park it would have to be used to move the car. It does not take, under any reasonable set of conditions, 199 Whr/mi to move an X a tenth of a mile. 199 Whr expended over 1/120th of an hour means average,over the whole 30 seconds, power of 24 kW. The power meter never peaks this high let alone stays this high for the whole tenth mile run.

I keep posting data that makes it pretty clear that power consumed in park is accounted for and displayed. Could someone post some data that indicates that it isn't? I'd like to understand this. David99 reports that he has tested this extensively, Could you please post some of your please post some of your test data so I can compare it to what I am seeing.

While sitting in the car with the heater on and radio playing this morning I asked the navigation system to plan a trip to a SC some distance away. The energy display in trip mode showed that I would arrive there with 44% left in the battery. After some time the indicated reserve dropped to 43%. In the other mode the display indicated that I had 273 miles range left in the battery. After sitting there with the heater on and the radio playing for some time the indicated remaining range dropped to 272 miles and after another approximately equal interval it dropped again to 271. This I also take as a pretty solid indication that the displays are accounting for energy used when the car is in park.

Depends on how long you are in park.

If you watch the automatic trip odometer and put it in park with heat on. And wait a minute then back in drive it will NOT reset the trip odometer and will include the the energy in park. But if you wait a certain amount of time it will when you go back in drive it will consider it a new trip. It won’t log the time between. Nor if you say preheat the car and get in and drive it’s not included.

Basically it tries to guess that you are still in an active trip and tallies the whole trip. If you just stop to drop someone off or pickup. It’s still the same trip.

For all practical purposes it does not track the bulk of being in park. Unless in park for a very short period sandwiched between two drive sessions.

If it did track parking my lifetime wh/mi would be through the roof. It’s at 270 wh/mi for 4000 miles. And a whole lot of working on the car in park and heater running.

 

[mxnym]

BTW the first 10th does occasionally show consumptions as low as 1200 Wh/mi but it is usually 2500 - 3000 and in one case over 7000.

Evidently it does. Yesterday morning the display showed 900 Whr/mi going down my 0.1 mi driveway at 10 mph.

One of these things is not like the other... I provided numbers that could absolutely explain what you're seeing, and you refuted with numbers that were 2-3 times my assumption. Now you're suggesting a number lower than my assumption implies something that the numbers I provided could already easily account for...

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.

Also, regarding the numbers being counted (or not) toward a trip when the car is NOT moving, I have already pointed out that there are multiple states. I am confident that when it says "Car Off" in the IC, the numbers are NOT counted toward trip meters. Another poster has stated that based on CANBUS readings, the numbers are also NOT counted when the vehicle is in Park (which is an option in the "PRND" state). We don't know what testing methodology that tester used, so it is possible the energy drawn in Park is counted sometimes (for instance, after shifting into Park from Reverse, Neutral, or Drive, so long as you shift back into Reverse, Neutral, or Drive before entering the "Car Off" state), but I do know some other things:
1) "PRND" state is not entered until you press on the brake, but you can sit in the vehicle with accessories on without stepping on the brake.
2) The "Since hh:mm" trip meter's time is set when you switch into "PRND" state (further supporting the theory that the draw while in "Car Off" is not included in the "Since hh:mm" trip meter).
3) "PRND" state is exited after you sit in the vehicle in Park for roughly 15 minutes.

Between the numbers that I did, in fact, provide, the three points directly above that involve consistent vehicle behavior, experiments that I have suggested, and experiments that others have suggested, you should be able to prove something using the scientific method, but further discussion revolving around theories is starting to look a bit pointless.

 

[ajdelange]

If you watch the automatic trip odometer and put it in park with heat on. And wait a minute then back in drive it will NOT reset the trip odometer and will include the the energy in park.

That's what I see.

But if you wait a certain amount of time it will when you go back in drive it will consider it a new trip. It won’t log the time between. Nor if you say preheat the car and get in and drive it’s not included.

I'd consider overnight long enough in park to reset the meter. When I unplug the charger, turn on the heat and sit in the car in park for half an hour the energy used is clearly logged or at least the display shows energy used for something other than moving the car the first tenth mile.

Basically it tries to guess that you are still in an active trip and tallies the whole trip. If you just stop to drop someone off or pickup. It’s still the same trip.

Roger that. So that naturally causes us to as the question "Why would Tesla give us accurate data if we stop for 5 minutes to drop someone off but inaccurate data if we go into the mall for an hour thus giving us an incorrect picture of how the car is performing, inaccurate range predictions, inaccurate margins at destinations etc?" If this obvious error is known, why hasn't it been addressed? Hasn't anyone reported it to them?

For all practical purposes it does not track the bulk of being in park. Unless in park for a very short period sandwiched between two drive sessions.

It certainly appears that it does. Can you give some example numbers that would contradict what I am seeing?

If it did track parking my lifetime wh/mi would be through the roof. It’s at 270 wh/mi for 4000 miles. And a whole lot of working on the car in park and heater running.

That's remarkably low for an X under any circumstances. ABRPs real world data shows a minimum of about 321 at the sweet spot (40 mph).

I've only logged about 690 mi at this point (95% of it during an unusually cold January) and showing lifetime utilization of about 350 Whr/mi. I too have spent lots of hours (proportional to a month's ownership) sitting in the car with the heat on reading the manual, experimenting with displays, communing with my new toy and gathering data to help me either support or reject the hypothesis that the car does record in park, whether at McDonanlds window or parked overnight.

It's helpful to look at numbers. 690 mi @ 350 Wh/mi is 241.5 kWh. If my average speed is 45 (reasonable for the kind of driving I've done so far) then I've spent 15.3 hr on the road with the heater on for all of it. Assuming it takes 1 kW for the heater (3412 BTU/h) that would suggest 15.3 kWhr for the heater on the road at a cost of 22 wh/mi. If I sat in the car for an additional 5 hrs with the heater on without moving that would be an additional 5 kWh or 7.2 Wh/mi. The tax for sitting in the car 33% of the time I have actually been on the road in it is pretty small - I might expect 343 wH/mi had I not done that. And the tax for using the heater whilst driving isn't that big either. Thus I don't think your consumption would have been huge if the car accounted for energy use whilst in park.

 

[ajdelange]

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.

One of these things is not like the other... I provided numbers that could absolutely explain what you're seeing, and you refuted with numbers that were 2-3 times my assumption. Now you're suggesting a number lower than my assumption implies something that the numbers I provided could already easily account for...

To travel a tenth of a mile at 15 mph takes, according to ABRP data, 46 Whr. If the trip meter displays 900 Whr/mi for that first tenth then you used 90 Whr to make that trip and 44 Whr were logged for something else. If the trip meter displays 1200 Whr/mi then you used 120 and 74 Whr were logged for something else. If the meter says 7000 then you used 700 and 654 went for something else. If the trip meter says 460 Wh/mi you used 46 and nothing was logged to anything else.

Forgive me, but the numbers you gave explain nothing contrary to what the observations show. They simply illustrate that in an electric vehicle there is a tax for running the heater before you take off and in an ICE vehicle there is a tax for starting the engine, moving big end bearings through buttery oil, extra loading on the alternator because you've just taken a big chunk of charge out of the battery and that the Wh/mi or mpg meters would both reflect this. I've seen numbers above 1000 and below 1000. Usually they are above but that's because I have been running the heater for a long time. It will be interesting to see what happens when the weather warms - supposed to today.

1) "PRND" state is not entered until you press on the brake, but you can sit in the vehicle with accessories on without stepping on the brake.

True

2) The "Since hh:mm" trip meter's time is set when you switch into "PRND" state (further supporting the theory that the draw while in "Car Off" is not included in the "Since hh:mm" trip meter).

Also true but it that does not steer us towards the null hypothesis. The meter reads against distance, not time. There is still some question in my mind as to where the origin is. Presumably the last OD reading to 0.1 mile precision.

3) "PRND" state is exited after you sit in the vehicle in Park for roughly 15 minutes.

Also true

Between the numbers that I did, in fact, provide,

Forgive me again but the only numbers I can find from you in this thread are...

Let's assume your "huge spike" may be 1200Wh/mi vs a highway average of 337.5WH/mi (July2017+ X100D).

337.5/1200=.28

These are hypothesized numbers. I am asking for real numbers read from the meter in your (or anyone else's) car.

...you should be able to prove something using the scientific method, but further discussion revolving around theories is starting to look a bit pointless.

It should be clear that I am, informally, using scientific method. It started with the observation that there was a spike at the beginning of trips that was bigger than the spike in leaving a stop sign. This led to the formation of a hypothesis that the trip meters were accumulating energy usage before departure. That was followed by recording data from trip meter readings on actual trips. All my recent posts on this subject have been reports of what those trips showed and whether they support or refute the hypothesis. So far they are supporting it. It seems that you are the one evoking theories while I am actually going down the scientific method path.

If you are familiar with the scientific method you know that you can prove nothing by its use but only show that the null hypothesis is true with low probablity.

None of this means that your thoughts are not of some value.

 

[mswlogo]

It certainly appears that it does. Can you give some example numbers that would contradict what I am seeing?

I have not timed things down to a stop watch to say. But I will say, no matter how much I preheat the cabin I always get a good spike at the start of a cold morning. But there is no way it included the preheating (the spike is not high enough to account for it). But if I turn heat OFF, just before I put it in drive it will go right to 240 wh/mi (or even less) even with 90% limited regen.

For fun, I've been running with heat OFF. My killer cold battery, no regen short 5 mile commute is about as bad as you can get for efficiency in cold climate.

I got around 230-240 wh/mi every time with heat off. With heat on it will average around 300-330 wh/mi but it might start off at 800 wh/mi for the first 0.5 miles. It does not seem to matter if cabin was preheated or not. But it does matter if heat is on or not.

In other words if it's cold out and heat is on there is some fixed cost at the start and it doesn't seem to be cabin temperature (relative to outdoors) related.

 

[mxnym]

These are hypothesized numbers. I am asking for real numbers read from the meter in your (or anyone else's) car.

Actually, they are numbers I saw every time I filled up for years in a previous ICE compared against numbers I see every morning in my current X100D.

It should be clear that I am, informally, using scientific method. It started with the observation that there was a spike at the beginning of trips that was bigger than the spike in leaving a stop sign. This led to the formation of a hypothesis that the trip meters were accumulating energy usage before departure. That was followed by recording data from trip meter readings on actual trips. All my recent posts on this subject have been reports of what those trips showed and whether they support or refute the hypothesis. So far they are supporting it. It seems that you are the one evoking theories while I am actually going down the scientific method path.

If you are familiar with the scientific method you know that you can prove nothing by its use but only show that the null hypothesis is true with low probablity.

None of this means that your thoughts are not of some value.

The surest way to gather control data would be to quickly reset a relevant meter at a stop sign. You haven't done that and keep brushing similar suggestions from others off as well.

That discussion aside, here are some real numbers from a recent trip I just happened to remember to pay attention for:
Outside temperature: 55 degrees F
Time X100D parked: ~5.25 hours
Regen availability: ~50%
Accessory state: Range Mode OFF (always), Media PAUSED (Local USB), HVAC OFF, ??? ??? (maybe driving lights were on, I don't know, shouldn't really matter in this scenario)

Given the above variables, I got in my X100D and immediately put it in drive to start a trip. I gingerly accelerated down a mild but noticeable incline, up a more mild / less noticeable incline of slightly more length, and then began to coast down a hill to a stop sign. Between the end of this incline and the start of my coasting, my first reading came up:
726 Wh/mi with .1 mi logged
Shortly before I stopped at the stop sign at the end of this short downhill coast, the reading changed:
242 Wh/mi with .1 mi (still) logged
I was fortunate that there was no traffic, and I was able to immediately turn onto the highway and begin accelerating to 55 MPH at a rate that is certainly slower than the average driver (not to mention the average Tesla driver). When I reached 55 MPH, I looked at the meter again and had the following reading:
782 Wh/mi with .3 mi logged
From there as I watched, the meter, this reading slowly decreased (it was down in the 600s while still reading .3 mi).

Perhaps the problem is that you are treating the .1 mi reading as a precise reading in your math even though you have already acknowledged that it is obviously rounded most of the time.

The fact that a 726 Wh/mi reading was followed by a 242 Wh/mi reading while the same tenth of a mile was displayed at the beginning of a drive seems like pretty solid evidence against any "departure tax" accruing during the 5.5 hours I was parked.

The fact that a higher reading was shown after a subsequent acceleration at .3 mi than the first reading at .1 mi also seems like pretty solid evidence against the very same.

The experience to know that if I drove 10 miles and came back to that exact same stop sign and took out the exact same way, the reading would not have jumped on that acceleration seems like pretty good support for the suggestion that the data used and averaged together starts when the trip starts (at hh:mm in "Since hh:mm").

The fact that I have observed average MPG meters in ICE vehicles behaving the exact same way for decades seems like pretty good support for the not-so-hypothetical scenario I previously laid out.

 

[David99]

While sitting in the car with the heater on and radio playing this morning I asked the navigation system to plan a trip to a SC some distance away. The energy display in trip mode showed that I would arrive there with 44% left in the battery. After some time the indicated reserve dropped to 43%. In the other mode the display indicated that I had 273 miles range left in the battery. After sitting there with the heater on and the radio playing for some time the indicated remaining range dropped to 272 miles and after another approximately equal interval it dropped again to 271. This I also take as a pretty solid indication that the displays are accounting for energy used when the car is in park.

We need to distinguish between the different ways the car shows info and different states it is in. The range estimate (percentage or miles) will always show the remaining energy in the batter as range or a percentage. Any energy taken or lost from the battery will be accounted for regardless of what mode, state or condition the car is in. Nothing is every forgotten or lost or not accounted for. The BMS works all the time. That's why range will always be correct.

The trip meters are a different animal. They show energy used, not range. There are different trip meters. The one automatically started when you are done charging. The one automatically started when you start to drive. And the two you can reset on your own. The one started automatically when you start a drive shows time, distance and consumption, but not energy. The one since last charge and the two other show energy and distance and consumption, not time though. So there are different ways to show the data. For my testing I used the two trip meters you can manually reset.

In addition to that I have a CAN bus reader hooked up to my car where I can see energy consumption at all times, any state or condition or mode the car is in. I can see the counter that the BMS uses to ultimately calculate the remaining range. I can see it count all the time in real time.

The test I just did a few days ago is this: Reset trip A in the car. Reset my CAN bus counter. Car is in P. Turn on the heater full blast. Through the CAN bus I can see the car using aprox 6 kW. After aprox 20 min I see the CAN bus counter shows 2 kWh energy used. I see the rated range has dropped 6 miles. I see the trip meter still shows 0 kWh. I turn off the heater, I put the car in D, I start driving. The trip meter does not jump up to 2 kW. After driving for 0.2 miles the energy consumption shows 345 Wh/mile (or something around that number).

If I do the exact same test as just described keeping the car in D (holding the car with the brake), the trip meter will 'catch up' showing the energy used while the car was not moving. I have to drive at least 0.1 or 0.2 miles for the trip meter do so.

This is in my Model S 85, firmware 2018.50.6 4ec03ed (installed 6 days ago). Maybe other cars and other firmwares do it differently.

 

[ajdelange]

I've gotten quite a few more readings in warmer weather and haven't had a chance to look at them yet and mix them in with what you guys have reported (thanks) but I have seen some squirrelly stuff such as the the meter indicating whr/mi numbers before the miles increments. I have no idea how to explain that.

I have always done computations with floating point but am well aware of quantization noise and even suspect that it may be responsible for some of this.

I have not reset a trip meter at a stop sign because ostensibly it isn't necessary. If the meter reads 4.2 mi and 300 wh/mi when you hit the stop sign then you have used 1260 ± 0.6 wh energy (including rounding error) so far on your trip. If the next reading is 4.3 and 309 we conclude that a total of 1363.1 ± 0.62 whr have been used so that in that first tenth from the stop sign 101.1 ± 0.8 wh were consumed which is 71 more than the average up to that point so we assume the extra 41 went to acceleration, the heater, the radio etc. Thus it doesn't appear that
1) Round off error is significant here
2)That you would need to reset a trip counter at a stop sign to get good info

I am most interested in the CAN bus reader. Can you tell me about that? Is it some Fluke thing that is going to cost me half the value of the car or some Arduino shield...?

 

[mxnym]

I've gotten quite a few more readings in warmer weather and haven't had a chance to look at them yet and mix them in with what you guys have reported (thanks) but I have seen some squirrelly stuff such as the the meter indicating whr/mi numbers before the miles increments. I have no idea how to explain that.

I have always done computations with floating point but am well aware of quantization noise and even suspect that it may be responsible for some of this.

I have not reset a trip meter at a stop sign because ostensibly it isn't necessary. If the meter reads 4.2 mi and 300 wh/mi when you hit the stop sign then you have used 1260 ± 0.6 wh energy (including rounding error) so far on your trip. If the next reading is 4.3 and 309 we conclude that a total of 1363.1 ± 0.62 whr have been used so that in that first tenth from the stop sign 101.1 ± 0.8 wh were consumed which is 71 more than the average up to that point so we assume the extra 41 went to acceleration, the heater, the radio etc. Thus it doesn't appear that
1) Round off error is significant here
2)That you would need to reset a trip counter at a stop sign to get good info

I am most interested in the CAN bus reader. Can you tell me about that? Is it some Fluke thing that is going to cost me half the value of the car or some Arduino shield...?

If you've seen energy used at 0.0 miles, based on what I believe to be true from information posted in this thread and the assumption that the trip meters will update in time increments as opposed or in addition to distance increments, that would imply that you have shifted out of Park and moved less than .04 miles over a set amount of time. Have you considered this?

The trip meters are a different animal. They show energy used, not range. There are different trip meters. The one automatically started when you are done charging. The one automatically started when you start to drive. And the two you can reset on your own. The one started automatically when you start a drive shows time, distance and consumption, but not energy. The one since last charge and the two other show energy and distance and consumption, not time though.

If you have the "Since hh:mm" meter and the "Since last charge" meter on the IC, you should be able to unplug the vehicle, do your tests, and see whether or not the kW in the "since last charge" jumps more when you've running max heat for 15 minutes (1.5kW worth of electricity?) after unplugging and then turned it off before you ever turn the car on vs when you start driving with nothing on immediately after unplugging. Especially assuming that the results of those two behaviors are similar, you might be able to take the kW drawn from the "Since last charge" meter to extrapolate the miles driven in the "Since hh:mm" meter to a smaller unit than tenths of a mile from the Wh/mi readings on both meters (that presumably match), while this would be easiest on the trips immediately after unplugging, it might be feasible with a doubled margin of error on other trips if you deduct the "energy used" you started the new trip with.

I'm not sure what you're looking for, but it seems like that would help fine-tune the data and prove or disprove any error you believe you are seeing.

As it is relevant to our discussion and also the OP of this thread that I notice we have segued from, the "Since last charge" meter in my 100D showed roughly 25kW used yesterday when my battery % was reduced by roughly 30%. This is not uncommon, but it is another example of why I don't believe energy used during the "Car Off" state (and apparently in Park when the car has just been moved into the "PRND" state) is accrued on these meters. It is also an example of where some of that 50% discrepancy is coming from. Vampire drain, accessories used while the car is "off / parked" and inefficiencies in charging all contribute to more power coming from the wall than what any Wh/mi meter shows.

 

[fbitz777]

Hi Everyone,

Just reached first 1000 miles so I checked my stats.

I'm averaging about 400Wh/mile so theoretically after 1000 miles, I should be at 400kWh of electricity used.

I have a meter attached to my charging outlet and it's at 601 kWh, about 50% more than expected.

Just wondering if anyone else ever studied their actual electricity draw and if this is within the realm of normal.

You got me doing that test as I was curious too:
did a 1000 mile test and averaged 398wh/mi or 398kwh. My meter used 568kwh so 42 percent more

Note that is was pretty cold here and never got more that 150 range on a full battery. Also lots of vampire drain losses.
I should do much better as the weather warms up.

 

[ajdelange]

Keep in mind that the rectifiers are not 100% efficient. Also note that if you leave the car plugged in the charging system will make up the vampire losses. This vampire losses thus appear on the watt hour meter but do not in the wh/mi calculations. Your numbers show overall efficiency of 70%. The rectifiers/voltage converters are probably 85% efficient so this means vampire losses of about 15%.