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Rated Miles, Projected Miles, and Actual Miles

We took a drive yesterday from Seattle to Bellingham and back. The display showed 230 rated miles when we left, and 30 rated miles when we returned. The projected miles jumped around some, but because I was driving conservatively, projected miles generally tracked within about five miles of rated miles. In any event, I returned with about 30 projected miles left also. However, the odometer showed that we had traveled 180 miles, not 200 miles. So what do people use to determine how many "actual" miles they may have left? Clearly both the rated and the projected numbers were overly optimistic.

@ DouglasR and CnJsSigP - I'm pretty sure kWh lost while sitting are not reflected in the trip kWh and Wh/M calculations. In the 7 months we've had our S, we driven 6668.6 miles, consuming 2115.4 kWh and averaging 317 Wh/M as displayed in the Trip B data display. During this time frame, our Model S has stored 2847 kWh into the Battery as recorded at the end of each charge cycle. The difference between the two kWh numbers are the kWh consumed by the car when it is not being driven. In our case this works out to about 110 Wh/M. In addition to this energy loss, there are losses of about 10% during the charging process. So in our case, although our average Wh/M to propel the car is 317 our actual cost to drive the car is about 474 Wh/M. When Tesla implements the sleep mode to reduce the energy consumed when the car is not being driven, this number should decrease significantly, to perhaps 375 Wh/M.

I agree with Rod and Barbara regarding trip kWh, but the 110 wh/m is much higher than my experience. My detailed findings were posted under where did the 19% or 23% go? I thought 23% more electricity use than stated by Model S was bad enough.

Good stuff R&B. I agree with that, but think that the sitting usage and moving usage numbers might splay more if the car is left unplugged. I haven't tried this yet, but does that total number of kW recovered slowly increase as it sits plugged in, vs. leaving it un plugged and having to charge up after 3 or 4 days and recovering 30 or so miles?
Theoretically that recovered charge number should increase about 3kW/day using 10 mile loss at 300Wh/mi formula.
Hmmm...

So it was a breeze trip. I charged to standard which was 276 miles and then added 9 more miles while I made my latte and breakfast and preheated. All my discussion for now is with ideal and standard.

83.2 miles at 23 degrees F used 26.2 Kw and at the end of the first leg displayed 183 miles remaining.Projected range only goes as far as the last 30 miles so it was at 196. My toes were frozen but I wanted to be fair to the car and I am a very empirical guy. I did use the heat for 40 seconds but worried so turned it off and thought about how to explain it to the Forum. I did have about 45 minutes of phone calls. Oh, by the way, the first 8 miles were stop-n-go city as were the last 4 miles. Tail Wind was about 4mph.Set cruise at 56mph.Seat heat1-3.

The S sat for about 75 minutes before I could get a spot at the 110v outlet. Plugged in then and it started a 3mph but went to 4mph in about 30 minutes or so. At that 75 minute mark the display showed 175 miles remaining. At 3 hours after arrival (1 hr 45 min plugged in) the display dropped to 171. After 6 hours it rose to 180.

The 2nd leg of the trip was a blast. Heat seat 1-3. It was starting to snow and it was 30F. Quartering left tail wind for miles 10 thru 20 and then headwind the last 60ish miles of 7-14mph. Cruise was set at 55 but that went to 65 at about mile 35 and heat went to High on both sides. I used Slacker/an accessory Sirius radio and 20 minutes of phone. A little Web and GPS by accident but I don't know if that uses measurable power. I was clearly in the clear and punched it a few times to pass, avoided drafting because I don't want freckled paint, and there were a lot of trucks. So inpassant drafting was both positive and negative depending on the wind and the truck. Rubber necking was hazardous as people swerved to look at the S, very long semi's included.
This leg was 81.3 miles 29.6Kw and Average Energy 364Wh/mile
81 miles ideal range remaining, 58 Projected but that's kind of meaningless. The Rated Miles ended up at 71 miles remaining.

I hope this is useful to someone, sorry to the rest.

@Rod and Barbara

I just drove the car a short distance, and it appears you are right. At its maximum last night, I believe the car had about 244 rated miles (I saw it at 243, but it had already completed charging by then). When I took it out of the garage this afternoon, it had 237 rated miles. The seven mile drop should have consumed roughly 2 kWh. When I took it out of the garage, the trip meters showed 0 miles and 0 kWh since the last charge. Had my theory been correct, I would have seen the car "consume" 2 kWh in the first few minutes.

Instead, what happened was this: the same moment the meter clicked over to 0.1 miles. it also clicked over to 0.1 kWh. Now that is a rate of 1,000 w-h/mile, but I think it was high simply because of rounding (I was driving on a flat surface at around 20 mph). For the next few tenths of a mile, the kWh counter stayed at 0.1. It then gradually increased, with the average w-h/m settling around what I expected, 250-350.

So I agree that the trip meter records energy usage only while the car is moving. When I returned the car to the garage, rated miles were 234, somewhat less than what I would have expected from the recorded energy consumption of 0.3 kWh, but again, this discrepancy could have been due to rounding.

@drp very good-- glad your enjoying the ride.

Great info, @drp. So you lost a total of 3 miles with the car plugged in to 110v for six hours? Clearly worth doing if it means you can stay warm and enjoy your ride.

Douglas

I think the batteries started to cool quickly and the 110v took a while to get them going again before it could give back. Like Tesla says, Plug in when you can!!!! No matter how little the v's.

John

@R&B thanks for the post. I assumed that was the case. Thanks for the confirmation.

@ CnJsSigP – I don’t think it should make any difference if I charge the car one hour every night for three nights or just charge it for three hours on the third night. What does make a difference is how many miles are driven over the three-day period. If I drive 300 miles then the kWh lost while sitting idle are spread over 300 miles. If I only drive 100 miles then the same kWh lost while sitting idle are only spread over 100 miles and the Wh/M efficiency will be much worse. For example, if I had driven 10,000 miles over the last 7 months instead of 6,669 miles, then the energy lost while the car was not being driven would have been 73 Wh/M vice my actual experience of 110 Wh/M. By the way, I consider this level of energy loss while sitting idle very excessive and look forward to Tesla implementing a sleep mode that works. After 4+ years with my Roadster the energy loss while sitting idle is 17 Wh/M and I only average about 560 miles/month in my Roadster while I average about 950 miles/month in my Model S.

These are the reasons I can think of for plugging in every night:

* there is some "storage" charge level that optimizes battery life - I think it is around 60-70% of max voltage

* TM doesn't want you stressing (or complaining) about .5 mph loss when parked/unplugged (more if it is real cold out)

* just a good habit...less likely you'll get caught undercharged

@Rod and Barbara - your explanation matches my understanding after driving about 3400 miles in my S. Basically I've found that its not hard at all to meet the EPA (about 310 kh/mi) energy 'budget' if you do three things" (1) watch your average over 30 miles and attempt to 'beat' that target, (2) are smooth on acceleration as much as possible and (3) use Cruise control when possible possible because it really does reduce energy usage.

I'm coming to rely on my "Rated Range Remaining" display and as long as its greater then my navigation's distance remaining number (plus about 20 for my personal reserve) there is no range anxiety.

Bottom line: plan trips under 180 miles (starting out with a Range charge) and you can ALWAYS make it even in cold weather. Gradually work up to 200+ mile trips and you will see you can easily make those as well in most cases, especially as Spring starts to release us from sub-freezing temperatures.

I'm no longer obsessing over the "Energy" app and its 'instant' calculation and learning to love and appreciate the incredible accuracy of the Rated Range display.

Traveling (IMO) does not have to be so hard!

Pilot,
I second your motion about obsessing over the energy app and trusting the rated range. I pretty much nail the rated range. Now that I know the rated mileage display is my standard, I can take it easy on a longer trip and exceed that number, or let all hang out on a shorter trip and show those rubberneckers what an S is capable of!

When I'm on longer trips, I plan my stops ahead of time, and I leave lots of cushion for emergencies, so I am never worried about running out of charge or how much range I have left. I do pay attention, however, to the "average-consumption-since-the-last-charge" meter. That tells me whether or not my energy use is in line with my expectations for that segment of the trip -- i.e., whether it is significantly better or significantly worse than what I had planned, given the temperature, terrain, time of day, etc. If it is worse, I can adjust my speed and the climate control accordingly. If it is better, I can drive like CnJsSigP. ;)

I drove my model S from Seattle to Bellingham a couple weeks ago. According to the nav, 75 miles. (Actually Fairhaven). Plus I went to Green Highway charger (free!) and used a level 2 for an hour while I ate Added 15 miles rated range).

60 kWh car, started with range charge (showed 197 miles to start). Added 15 miles rated range. Drove 160 miles. Arrived home with 9 miles remaining.

197-160-9+15= 44 miles of range that I didn't actually get.

I drove at 65 and 75 on the way up, and at the speed limit on the way home. It was about 38 degrees outside.

The thing I find difficult to figure out is why I leave home with 184 miles of rated range, drive 22 miles to arrive with 150 miles rated (about 335 Wh/mi on the log) and when I go home it is down to 140, usually. I drive the car pretty gently, generally; there's traffic anyway.

Seems like even the rated (supposedly conservative) range overstates practical daily range pretty significantly especially if I go over to the other worksite during the day. Each 3 mile round trip seems to eat 7 or 8 miles of rated range. Yesterday I drove about 55 miles and used 85 miles of rated range.

I am going to ask about it at the service center... the car is only three weeks old.

Other than that it is great but if it can't really go a reliable 150-160 highway miles even superchargers won't help. Washington has lots of ChaDemo on the 'green highway' but we can't use those.

I really like the car, otherwise, but this concerns me.

Oh and by the way, once the car charges, it doesnt top off even if plugged in. Mine is usually fully charged- 190 miles- by bedtime, and in the morning (6 AM) is down 6-8 miles. The car is in a garage with a temperature of about 50-55 degrees.

@DTesa - I certainly share your observation and concern. This may be a too simplistic answer, but what I try to keep in mind is to achieve Rated (EPA) miles your energy budget is about 300 Wh/mi.

I still feel good about my driving when I am under 350, but thats gonna cause a 15% reduction in range. So to relax I just assume I'll achieve 10-15% less range plus require I end the trip with at least 20 Rated remaining (for reserve and mental comfort).

Bottom line: I think the Rated Remaining is actually very accurate you just need to understand that unless you are driving under ideal conditions and for quite a long time (road trip) you will be 'over budget'.

And the answer to over budget is to watch the average Wh/mi since last charge on the TRIPS app and adjust your driving to achieve 300'ish –or– know you have a charge stop like you did and make up your 'over budget' energy that way.

Its complicated, but not too complicated IMO.

@ DTesa - I agree with pilotSteve's comments about Rated Range. The actual Rated Range efficiency is about 307 Wh/M. With respect to topping off while plugged in, the car will only check its state of charge every 24 hours. If the state of charge has dropped more than 3%, the car will restart charging and top itself up. If it hasn't lost more than 3% in that 24 hour period, nothing will happen.

@ DTesa "Oh and by the way, once the car charges, it doesnt top off even if plugged in."

I talked to TM about the issue you described (it happend to us both at home at at the Folson & Gilroy Superchargers) and they pushed a software fix to my car and I haven't had it happen since. Might be worth a call to them.

I've made a couple long trips including 320mi RT to Boston. For max range I warm up battery and cabin to 70 degrees before leaving, set car to range model, set cruise control to a speed that puts 5mi avg watt line on top of rated line (i.e. a little over 300 Wh/mi) and then with some margin of error at 30-40 degrees temp outside and little net altitude change or headwind that actual GPS miles = rated miles = projected miles over long distances (100mi+). Makes the math pretty simple if you need to reach for range. Cruise control speed to do this is about 68-69mph on mine.

One more observation during a new test... maybe R&B can confirm this.
I have revised my thinking and I totally agree that the real world rated range comes in at 308Wh/mi. Simple test was to get my 30 mile avg to 308 and look at projected range vs the rated range on the dash and at at 308, both numbers match.
So I did an all day outing in the S this weekend. And I still fell behind the rated range by a few miles even though my Wh/mi avg for the entire trip was 294.
I left the house with 239 range. Drove a total of 174 miles and came home with 56 remaining. I think what the accounts for the 'lost' mileage is the fact that this trip started at 9am, and didn't end until 10pm. So I have documented that my S uses about 12-13 mile a day, sitting. So while a point to point 174 mike trip would have put me on top, the fact that it was an all day event, going from here to there and all around, all day, my range slipped a bit due to parasitic losses over time.
So if you are pushing the range for a trip, factor in overall time as well.

@ CnJsSigP - I agree with you on both counts. The test you describe is a good way to see real time data linking rated miles and rated range efficiency. I find a bit of scatter in the data, but over time the average number I have observed is about 308 Wh/M. As you describe, any trip that includes stops must account for both energy used to propel the car and energy used while sitting idle.

3 months and 3800 miles later, I have done lots of calculations from Wh/mile to electricity PG&E delivered to me compared to what the Model S instrument panel claims that I used. Now I have the following rule of thumb.

I consider myself average in driving aggressiveness. My longest trips have been 250 miles in one day and 470 miles over 32 hours.

Realistic real world range on max charge is 200 miles, which works out to 75% of 268 miles. Reasonable driving, not more than 70 m/hr, I can get 80% of 268. More aggressive driving, plus some waiting, then 70% of 268 is what I get.

On my 470 mile trip, averaged 350 Wh/mile. Of course, the Model S used more than 350 Wh/mile, as the instrument panel does not report losses while sitting. 350 Wh/mile is also my Model S lifetime average.

It may have been mentioned in this thread earlier, but I see that there is a line drawn on the "Energy" app graph to represent Rated usage, at about 300wH/hr. If you change the display "Setting" to Ideal miles, the line appears to be at about 280wH/hr. Would seem this would be a good visual method of tracking to a range while driving.

I have a 226 mile leg I'm planning in May from Tucson to Yuma. My previous record is 214 actual miles, indicated 272 - 30 = 242 miles. There was a 600 ft increase in elevation, with average speed of about 60mph. The Tuc/Yuma leg has a 2,400 ft drop in elevation and would be plenty warm. I'm trying to figure what speed/wh/hr I will need to average to make it with 20 miles of rated range left. Basic geography should tell you that there are very limited charging options until Yuma. I'm thinking 55mph average. On an interstate with a 75mph speed limit!

As I had mentioned earlier in the thread, I've been working on a "Route Energy Planner" that estimates the energy usage for a specific route accounting for speed, hills, temperature. Currently, I think it is within 5-7% and we're working on tuning the calculations and integrating with weather for wind/temperature. It is "alpha test" level if you want to try it at http://evtripplanner.com/planner/ - please let me know how accurate it seems for your trips and provide any feedback! Besides the calculator, I have other reference charts/spreadsheets posted at http://EVTripPlanner.com/

@cliff - I'm delighted to see this tool is up and working (albeit alpha). Can't wait to test it out!

William9;
Have you checked non-superhighway routes, and the location of KOA sites?

Brian H: You ever looked at a map of Arizona? Tucson to Yuma is a bunch of cactus and roadrunners. There is one RV park in Gila Bend a little less that half-way. But that's it. I have heard well-founded rumors that Yuma is the site of a future Supercharger for the Phoenix to San Diego crowd.

William9 - I too just completed the Barstow-Kingman and back route the past week - 216 miles actual (thanks for your logs BTW). Used 218 rated on the way to Kingman (292 Wh/mi) and 212 on the way back West (282 Wh/mi) - so nominally ran right around the EPA range. About half the run was between 55-60 running with empty trucks who could go up the hills as easily as down. When we hit AZ border, everything increased due to the speed change - and ran closer to 65+. Did a Range charge both times so had approx 50 miles in the tank at the end. Return trip was a bit faster as I was more confident and it was day time instead of night when I was heading east.

And to put this in context - most of I5 from Bay Area to Barstow was between 350 - 390 Wh/mi - but that was w/ CC set well into the 80's, but with the Supercharger spacing there, the trip was to enjoy driving the car on the open road.

So my take-away from my first road trip (2000 miles in 7 days) was that I really enjoy driving the legs <200, but that 230 or so would be my comfort level if I had to stretch it (and keep 30+ miles for the unexpected). And before I get shouted down, yes elevation change and ambient temp need to be factored in when pushing things a bit - both sound ok for your trek.

That's turning out to be one of the real attractions of the SCs: they allow uninhibited car-fun. Easy irresponsible driving! ;)


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