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Survey: Rated Range and Average Energy Tesla Model S

In an attempt to answer the question "Is related range related to driving habits?"

We have heard from Tesla employees that there is a correlation, some drivers say no.

Please fill out this four question survey monkey after charging up your car. A summary of the data will be provided to this forum once collected. Thanks.

http://www.surveymonkey.com/s/569L5MJ

sorry for the typo, should have been "is rated range related to driving habits"

Oh, I misread it first as "driving rabits"... oops.

A few weeks ago I posted a similar survey, but it got buried in a different thread, so it only generated about 30 responses so far (most of which I entered myself after looking into various cars at the Menlo Park Coffee and TESLIVE).

Using the Energy App., you can calculate how many kWh the app. believes are available for use (average kWh/mi * projected range, when average selected = total kWh available).

If you divide kWh available by 300 to 309 Wh/mi (it varies from car to car), you will get the EPA rated range number that is displayed on the instrument panel. There is just no apparent correlation with tire size, battery size, Performance/Standard, or driving habits as measured by the trip meter. Why the rated range calculation varies slightly from car to car remains a complete mystery. It would be nice if an engineer at Tesla could explain it.

On theory is that the fixed Wh/mi no. for each car is correlated to all options that affect the weight of the car, such as the pano roof, the twin charger, child seat, etc., but one would think that the battery size and tire size would be far more dominant factors than these other things. Yet there seems to be no correlation whatsoever, so I'd really like to understand how the Model S chooses which fixed number to use to calculated rated range.

Hi Bob,

I never saw your survey. I check out the Tesla Motors Club forum a lot more than this one. I have gotten a reasonable number of responses so far. Perhaps we can merge our data in a week or so? I'd be happy to take your data in for my five questions.

I would love to have a Tesla person from the engineering department answer this question myself. But in the spirit of reverse engineering I'll do this.

I don't expect the options to have much difference as that would be more a minor weight factor. So far I am surprised how consistent the data is for most cars.

I'm "Owner" on the Tesla Motors Club Forum and my blog is teslaowner.wordpress.com

In May, because of lost rated miles after a Standard Charge, I tried to understand if Rated Range was modified for driving style as some have suggested. I took a slightly different approach based on the theory that Ideal Range would likely not be modified for driving style and only reflect the state of charge of the battery. If this is true then Rated Range as a ratio to Ideal Range would vary by car if driving style is a modifier to the calculation of Rated Range. I took a small survey and asked Tesla the question below followed by their response.

Question to Tesla: my rated miles as a ratio of ideal miles has been running 86.8%. Today I had 236 rated and 272 ideal miles. I looked at the cars on the showroom floor, one had exactly the same ratio, but the other car had a ratio of 88.6% with rated miles of 235 and ideal miles of only 265. I am under the impression the calculation of rated miles changes with driving style and temperature conditions. Do you think it might be possible my ideal range, which I never look at has been constant after a charge, and the rated range, which is adjusting based on driving conditions has adjust downwards?

Answer from Tesla Ownership Experience. The most likely reason for the discrepancy between the vehicles in our showroom is slight variations between software versions. Only projected range is designed to adjust based on driving conditions, Rated range does not have a variable that adjusts. I’m not sure why you Model S originally had such a high estimate on a standard charge in rated range initially, but settling to about 235 miles range sounds very normal.

Interesting is that my currently my ratio has gone up to 88.2% and has been consistence at this ratio since I last recorded this information at the end of May. I'm not sure if this is after the software upgrade, but is clearly a difference from May 2 when I drafted the email to Tesla. So, I ask, does this ratio vary and may account for the feeling of lost Rated Range?

Good blog. Lots of material there.

@ TeslaOwnerBlog – Knowing the rated range at the end of a charge cycle is not the same thing as knowing the rated range Wh/M. The rated range at the end of a full non-range mode charge depends on a number or number of things such as:
- What charge level is selected (50% to 100% available in software v4.5)
- How long has it been since the charge cycle completed (vampire load drains miles in software v4.4 and prior, even in software v4.5 I see slight decreases in the rated miles if left plugged in after the charge is complete)
- How new is the battery (batteries lose capacity as they age)
- How close is the battery to a nominal spec battery (manufacturing tolerances likely mean that every battery does not have the identical capacity; through extensive data collection I determined that my Roadster started with a 98% capable battery)

The rated range Wh/M is not dependent on any of those items mentioned above. Bob W’s suggestion for determining the rated range Wh/M is an excellent method. My only addition would be to suggest that the readings be taken while the car is parked. I’ve taken readings while parked and while driving and found the parked readings to be more consistent.

Finally, I think any thread that gathers and presents actual data from vehicles should be a private thread.

@ Bob W – I entered a few data points in your survey. I will enter some more data. I was disappointed that the summary data does not present the calculated Wh/M for each car type. I was unable to use the raw data to make my own calculations since the raw data isn’t correlated to the car type. If what you say about the Wh/M not being correlated to car type, I wonder if the data needs to be tracked by VIN, or some other unique identifier, until we determine what the affecting factor or factors are.

I’m still perplexed that we have essentially the same vehicle and you calculate about 300 Wh/M in your vehicle and I calculate about 308 Wh/M in my vehicle. On the Energy app graph there is a solid gray horizontal line drawn at the rated mile Wh/M. This line is slightly wider than the horizontal grid lines. My rated mile Wh/M line is clearly displayed slightly above the 300 Wh/M grid line. If it were displayed at 300 Wh/M it would overlay the grid line and the only way to know it was there would be to notice that the 300 Wh/M grid line is slightly wider than the other grid lines. Is your rated mile Wh/M line drawn on the Energy app graph at 300 Wh/M or 308 Wh/M?

@Rod and Barbara

I'm curious about "vampire loss" while the car is plugged in. I was under the impression that "shore power" would be used when the car was plugged in. Therefore why would there be any loss at all while plugged?

@Jtod
I'm pretty sure that shore power is only in play if you are actively heating/cooling the MS, or if the battery capacity falls below some threshold.

@Rod and Barbara
We see right around 308 as well for Rated.

Still grinning. ;-)

@ jtodtman – In software v4.4 and previous the Model S “woke up” every 24 hours and topped off the charge if the SOC had dropped 3% or more from it’s previous value. The software v4.5 release notes state: “When Model S is plugged in but not actively charging, it will draw energy from the wall rather than using energy stored in the battery, e.g., when you’ve turned on climate control to cool/ heat the cabin or when you’re sitting in your car and using the touchscreen while it’s parked.” That statement seems a bit ambiguous since both examples described involve the owner demanding electrical usage above and beyond the vampire loss while just sitting idle. Based on some limited empirical testing I believe the wall power handles most of the vampire load but not all of it. For example, during a recent out of town trip I left my Model S plugged in for 8.8 days after the charge was complete. Normally the vampire load would have used about 105 rated miles during this time, but when I got home my Model S had only lost 4 rated miles (231 to 227). In addition, the energy draw from wall power to handle the vampire load is not recorded in the kWh Added display on the charging screen. For this reason, I don’t leave my Model S plugged in after the charge is complete because this behavior hides the power drawn to support the vampire load and I cannot accurately calculate the true cost to drive the car.

@Rod and Barbara

My survey asks folks to fill the rated range after a complete non-range charge, software version. I'm not going to consider vampire load as that would be too hard to ask folks to consider. Batteries don't generate oh so fast, but I do have some indications with folks with heavy mileage numbers. They age more due to use than time.

I don't see why this needs to be a private thread.

I've had my MS60 for a couple of months now and I'm getting about 2/3 of the mileage I'm expecting. I've been driving conservatively and reading about 327Wh/Mi over 750mi. The typical scenario is that I'll drive 20 miles with a couple of stops with no AC during the day, but have the Rated Range displayed on the dash drop by 30mi.

Putting a watt meter on the charger I'm reading for the last 24hrs 40.4mi travelled with the car reporting 12.8kWh consumed. This is with AC on for about 5mi and again during the day. The power consumed by the charger on the other hand is 21.5kWh. The difference is 316Wh/Mi (reported) vs. 532Wh/Mi (measured) which matches the experience driving.

Seems like I have to build in a 66% safety margin on trips, which now makes me wish I had gotten the larger capacity.

The other thing I can't figure out is why the dashboard and main console display different rated ranges (I've set the energy setting to rated and not ideal).

Rod, Barbara, shesmyne2

Thanks for the explanation.

nrb;
check with TM about that; those charging losses seem excessive. Your hookup may be (dangerously) under-wired.

They don't affect your mileage once charged up, though, just your expenses.

rnb:

I agree with Brian H that seems excessive. But 327 is pretty consistent with the "average" in the survey so far. But the data is also showing several folks achieving 250-300 range. Something I have not done myself, or gotten even close to.

Folks, please fill in your survey data, the more I can collect the more useful the data will be.

And thanks to those who have!

BrianH: The Tesla mobile adapter is plugged directly into the meter, so unless the adapter is losing energy there shouldn't be any wiring losses that the meter can see - certainly possible upstream as I'm having to do this on a 110V circuit to use the meter. However, my driving experience is that the car is consuming significantly more power than is actually displayed on the energy display. I wouldn't have thought that the Fan, DRL, Stereo, etc. would have accounted for that much, but its possible that the energy meter is only reporting energy consumed by the power train and not the accessories?

The energy meter can only report what power is flowing while the car is charging. There may by accessory draw at the same time, but it has nothing to do with driving usage once unplugged.

@ nrb – There are two issues at play in the scenarios you describe. The first is the rated miles used during your daily commute. If you average about 327 Wh/M, then you should lose about 23 rated miles for every 20 miles you drive plus about 0.5 rated miles for every hour your car sits idle (vampire load) during the time span you are covering.

The second is the energy draw from the grid to replace those rated miles. The energy draw you describe may be accurate depending on the efficiency factor of the Model S mobile adaptor for a 120V circuit.

I have additional information and data I can provide on these issues if you want to contact me at tesla25@verizon.net or exchange posts via a private thread on the forum.

Finally, I don’t understand your statement, “the dashboard and main console display different rated ranges.” What displays are you referring to? The center instrument panel displays rated range. The Charging screen on the touchscreen displays rated range and I’ve never seen this value not agree with the center instrument panel. The Energy app on the touchscreen displays projected range based on the driving experience over the last 5, 15 or 30 miles. The projected range and rated range are not the same thing unless you happen to be driving at the rated range Wh/M over the last 5, 15 or 30 miles and then the two numbers agree in my experience.

Ok, I'll take some screen shots and notes on driving the next couple of days, although I'm biking into work :)

I have gotten quite a few survey results! Thanks everyone. More data will make the report more statistically correct, so if you haven't filled it out yet, please do so.

Thanks
Tesla Owner

http://teslaowner.wordpress.com/2013/07/21/rated-range-survey/

@ TeslaOwnerBlog
Current results??

1. Rated range is a constant set by the EPA, given its own mixture of driving conditions, patterns, and speed. It is like the sticker stuck on the side window of a new ICE car: it is what the EPA says that car will do, under it's "average" conditions.

2. The EPA Rated Range for an 85 kWh battery is 265 miles. If you divide 265 into 85,000, you will arrive at 320.75471 (that's where my calculator runs out of significant digits) Wh to drive 1 mile. So if you drive in such a way that you use average 320.75471 Wh/mile, starting out with 85kWh in the battery, you can expect to go 265 miles.

3. Of course, it would be dumb to let the battery run down to 0 miles of rated range. I don't know how much reserve the battery pack has but I would not want to depend on it.

4. Each battery pack is slightly different. Each cell is slightly different. They can't be exactly identical. Some of us will be lucky enough to have battery packs with slightly higher capacity and some with slightly lower capacity. If the difference between the worst and best packs could be as much as 1%, that would be a difference of about 2.65 miles.

5. Driving conditions differ from drive to drive. Outside air temperature, hills, etc. Depending on what else the battery pack has to be doing (heating, air conditioning), this will influence the range you get. Not much, from what I've read, but a small amount. If that were as much as another 1%, that could be another +/- 2.65 miles, on the average.

6. There is what is called "vampire drain," which is the current required to keep the electronics in whatever state they're kept. That seems to be about 1/2 mile per hour. What most people don't seem to think about, is that this is going on 24 hours per day. It takes the same current to keep the electronics going, whether the car is on, off, driving, stuck in a traffic jam, going uphill or down, etc. It may be as much as a mile an hour but you don't notice it unless you're not driving the car when your intuition tells you it should be zero.

7. On the trips odometer screen, where it shows figures such as average Wh/mile since you first drove the car, since you set the trip odometer to zero, it is not at all clear to me where this takes into account this vampire drain. It might be that if the car sits still a lot, eating Wh driving the electronics (a small number), that might increase the Wh/mile figure you see, because it is including Wh used while the car is not moving.

8. The car charges and stops charging while it is sitting hooked up and charging. It clearly would be stupid to have it start charging when the charge has dropped by 1 Wh since it stopped charging. So it waits until the charge has dropped by at least 1 kWh (I don't know how much at least). If you catch it the second it stops charging, you'll have a higher number of Rated Miles to drive than if you catch it 3 hours later.

9. Different people drive at different Wh/mile, using different amounts of heating, cooling, media, etc. This all influences things. That more than accounts for day to day variation. Yes, the battery is probably losing capacity, but so slowly you're not going to notice anything on a day to day basis unless something is broken.

10. The decision by Tesla to give distances in Ideal Miles while Rated miles are much more realistic causes great confusion. It may have been a terrible mistake. That's like my wife figuring that since once, at 5 AM on a Sunday morning, it took us 2 hours and 15 minutes to drive to her father's house, that's all the time we need to allow under all conditions.

@NKYTA

I only have a very preliminary idea of the results. Surveymonkey lets me page through the data but I have to pay money for some automation.

I'm going to wait through the weekend before I do the detailed analysis of the data as I figure a few more cars will be reported by then.

@Rod and Barbara wrote:

"On the Energy app graph there is a solid gray horizontal line drawn at the rated mile Wh/M. This line is slightly wider than the horizontal grid lines. My rated mile Wh/M line is clearly displayed slightly above the 300 Wh/M grid line ... Is your rated mile Wh/M line drawn on the Energy app graph at 300 Wh/M or 308 Wh/M?"

On my Energy app, the solid line is drawn at exactly 300 Wh/mi; I see only one wide line in the middle, not a narrow grid line with a wider line above it at 308, like you see. Very interesting! My VIN is 28xx, delivered Dec. 27th, 2012.

Could it be that someone on the assembly line was personally responsible for hand entering the Wh/mi rated range number for each car, so each car got a different number (as shown on the Energy graph)? Could it possibly be geographically based? My car is in No. California.

I've posted the results of my survey responses to date in this public Google spreadsheet, which I've sorted by the last column (calculated Wh/mi used to determine the rated range). The number varies from about 300 to 321, with no apparent correlation to any of the other data collected by the survey.

Note that this is a completely different survey than the one created by the OP, @TeslaOwnerBlog.

@Rod and Barbara wrote:
"Based on some limited empirical testing I believe the wall power handles most of the vampire load but not all of it. For example, during a recent out of town trip I left my Model S plugged in for 8.8 days after the charge was complete. Normally the vampire load would have used about 105 rated miles during this time, but when I got home my Model S had only lost 4 rated miles (231 to 227)."

This is a bit misleading (and off topic, sorry). Obviously your car was waking up and recharging the main battery when it got too low, perhaps the day before you returned. You can verify this by looking at your energy company's web site if you have time-of-use (SmartMeter) data available.

If you car doesn't wake up to charge, the daily vampire drain will be the same, whether you leave the UMC plugged in or not.

Power is only drawn from the wall under three circumstances:

  1. The main battery is charging
  2. The heater or defroster is on
  3. The A/C is on

You can verify this by watching the UMC while you are sitting in the car. Turn on the A/C or heater. After a short delay, the green LEDs on the UMC start to move, because energy is flowing. Turn off the A/C, and wait 30 seconds or so. You'll hear a large relay click near the charge port, disconnecting the charger. If you're outside, you'll also hear a smaller relay inside the UMC click. The green LEDs will stop moving. No energy is flowing. None. Turn on the seat heaters. The UMC LEDs will not light. Wall power is not used to power the seat heaters.

The motor, heater and A/C are powered from the main battery. Everything else including the seat heaters, displays, computers, computer cooling fans, parking brake, relays, headlights, interior lights, door lights, horn, 3G hardware, USB ports, and 12V socket are powered from the 12V battery.

The vampire load (mostly the computers) drain the 12V battery, not the main battery. But whenever the 12V battery's voltage gets too low, the car automatically activates the DC-to-DC converter, and that is when some energy moves from the main battery to recharge the 12V battery. This is what we see as "vampire drain," because we can see that this recharging process reduces our rated range.

It seems to vary a bit from day to day depending on when your 12V battery is getting recharged. We have no control over this timing.

If you put a 12V trickle charger on the 12V battery terminals overnight, but leave the UMC completely unplugged, I predict that you would see almost zero vampire drain, because the 12V battery voltage will never get low enough to require any energy from the main battery.

Despite what the Release notes appear to say, the UMC supplies power to the main battery only, nothing else. If you're sitting in the car running the heater or the A/C, the UMC eventually activates, and the charging display shows 1-6 kW of power being consumed by the car. That power is flowing into the main battery, while the same amount is being drawn out to power the heater or A/C, so the main battery stays at a constant charge level instead of being drained.

Turn off the heater or A/C, and NOTHING will come out of the UMC (after about 30 seconds, the LEDs stop moving and the amps used drops to 0).

The only way the 12V battery can get recharged is by taking energy from the main battery (or an external trickle charger). The UMC has no 12V output. The charger(s) inside the car produce about 400V DC (?) to recharge the main battery. I'm 99% certain they do not also supply 13.8V to the 12V battery. It's a completely separate DC-to-DC converter that recharges the 12V battery.

You can verify this by leaving the car plugged in overnight, but set a charge time to 10 am. Wake up at 9 am and you will see how much vampire drain has occurred overnight. It will not be 0.

@Bob W
Very nice writeup! I'd expect similar detailed descriptions from the manual (if not there, yet).

There is a fourth circumstance when wall power is used that I forgot to mention: if it's very cold and the battery heater gets activated.

@ Bob W – Thanks for the info about the placement of your rated miles Wh/M line on the Energy app graph. Also, thanks for the link to your rated mile Wh/M survey results. I look forward to examining the results. I’m confident that we will eventually unravel the rated mile Wh/M mystery. And, finally another big thank you for a very thorough explanation of the charging behavior and vampire draw mechanization of the Model S. Everything you describe fits charging behavior that I have observed, but not thoroughly analyzed. One thing I am wondering about regarding the charging system is the display of the kWh Added on the Charging screen on the touchscreen. I use this number, adjusted for charging efficiency, to determine the amount of electrical power I draw from the grid to charge my Model S. Based on my recent experience where I left my Model S plugged in while I was out of town for 9 days, 12V battery recharging (required because of the vampire load) is not included in this value as the value did not change over the 9 day period. If I had remotely used the A/C to cool the cabin sometime during this 9 day period after the initial charge cycle was complete, do you know if the value of the kWh Added display would have increased?

@ Bob W – I’ve looked over the data you collected in the Google spreadsheet. Your data collection and calculation method is the most efficient one I am aware of, but even in a single vehicle there is a fair amount of scatter in the calculated Wh/M for the rated mile. For example, 17 data points in your spreadsheet were from my vehicle, and these resulted in Wh/M values of 303 to 310 with a mean of 307. Therefore one needs many data points from any particular configuration in order to determine a statistically significant Wh/M for that configuration. Only the 85 kWh Standard vehicle configuration has enough data points to work with. In an attempt to determine if individual cars may have a different rated mile Wh/M assigned to them I wanted to compare individual 85 kWh Standard vehicles. So I can identify the data points associated with your vehicle, can you post the Projected Range for the data points in the spreadsheet for you vehicle? Are there any other individual 85 kWh Standard vehicles in your spreadsheet with multiple data points that you are aware of?

@Rod and Barbara: Thanks for the kind words.

As far as I can tell, when a charge is complete, the model S displays how many kWh were added by the most recent charge, and only the most recent (when Charging Units is set to Energy rather than the default, Distance).

So, if you leave your car plugged in for a week, and it starts a charge cycle three different times, I think the display will only show you the results of charging for that third cycle, not a cumulative sum. And of course the power taken from the wall will be about 15% more than what the Tesla displays.

I'll do a test tonight with my Kill-A-Watt meter and 117V charging to see what it reports, that is, the difference in kWh used vs. kWh charged as displayed by the Model S.

I agree that even in a single vehicle there does seem to be some variation, but I've only seen it range from 300 to 302 in my own car, never more, so I haven't bothered to enter it more than once.

For all the data points you entered for your car, did you remember to press Average in the Energy App. before writing down the numbers? Did you ever record the numbers while the Model S was plugged in and the A/C was running? It's best to do it when not plugged in or not using A/C, otherwise the rated range number can jump around a bit.

For the loaner P85 I have tonight (thank you Tesla Fremont) I'm seeing 301.9 Wh/mi for rated range, and I can just barely see a hint of a thin 300 Wh/mi grid line just below the thicker rated range line in the Energy App, so it does indeed show you (in obscure fashion) what number your particular Model S is currently using to calculate rated range, a great observation.

As to the cause of the variation from day to day, perhaps it uses one number when your battery is nearly full, and another when nearly empty? The discharge curve may not be a perfect straight line, so perhaps the algorithm tries to compensate for this by adjusting the Wh/mi number to different values at different points in the discharge cycle. Except I see no obvious pattern when I sort the survey results by projected or rated range, so I guess that theory is not correct either.


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