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Some practical observations about the range of a 70D in winter

Discussion in 'Model S: Battery & Charging' started by David29, Feb 16, 2016.

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  1. David29

    David29 Member

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    The purpose of this post is to report some practical experience with a Model S 70D in winter. The focus is on energy consumption and real range, not on other aspects of performance.

    When I ordered my 70D last summer (July 2015), the model had only been available for a few months, and no one had experience with one in winter. I had been following Tesla for more than a year, had test driven cars two or three times, and had read a great deal, especially in the TMC and Tesla Motors forums. In addition, I had watched quite a few videos, mainly those created by Bjorn Nyland in Norway. Most of the videos reported experience with the 85 kWh battery models. My judgment from what I had read and heard was that the 70D would be a practical car for me. I was newly retired, and thus have no regular commute. I really did not know how much driving I would do but I did not expect to be driving further than the 70D’s range very often.

    In terms of winter battery range, I think I was influenced in my expectations by Bjorn’s videos. I can recall Bjorn saying that the cold did not have very much effect on his car’s range, and that rain and snow had more effect. What I now realize I did not appreciate was that Bjorn’s videos are mostly about very long trips, not the sort of local travel with multiple short trips that is most of what I do. In retrospect, I also think I was wearing rose-colored glasses to some degree. After all, I was smitten with the Tesla and was going to get one regardless!

    Now that we are a few weeks into winter, I thought I would offer some statistics on my experience with the 70D in winter. I have seen plenty of reports of individual trips in winter by various models, but not of average consumption over a period of time.

    And just to be clear – I am not suggesting that the 70D would perform significantly differently from the other battery configurations. It is just that I have a 70D, and it is the first year for this model.

    Weather -- Here in the Boston area, we had a very mild winter until just recently. December and January both ran well above normal averages. In January there were 4 days with high temperatures in the 50s, and many in the 40s. Daily low temperatures were mostly in the 20s, with only 5 days with a daily low below 20. February has been colder so far, but still somewhat warmer than usual, until this past weekend when we had a severe cold snap. I limited my statistics to January and February (through February 15), because December was so warm it would not be representative.

    In the 6 weeks of January and early February, I drove 1,045 miles. I tracked the kWh added each time I charged, and calculated the average Wh/mi. (In the interests of full disclosure, there were 3 data points for which I failed to record the kWh added by a charge, so I inferred the energy added from the reported change in rated range, using the figure of 292 Wh/mi, which corresponds to the rated range of 240 miles for the 70 kWh battery.)

    On average, my car used 549.7 Wh/mi. This seems quite high, and is equivalent to saying that the effective range I achieved was 127.3 miles, or 53.1% of the rated range of 240 miles.

    The consumption rate (Wh/mi) or effective range varied by date, of course, because of both weather variations and differences in my trips. The highest I saw was 725 Wh/mile for the frigid cold in this past weekend.

    But the cold weather was not the only factor at play here. The other factor, and maybe the most important factor, is that most of my travel is short trips, 5 miles or less, with occasional longer trips. So my energy efficiency is likely much lower than someone who commutes a long distance, for example. Every time I get into my car, it uses energy to heat the cabin, and then that energy is lost while the car sits idle between trips. Thus I probably use a lot more energy than many other owners because of how I use the car. So my statistics may well not be representative of others’ experience.

    One other comment I will offer, especially for people considering a purchase, relates to the effective battery capacity. Tesla refers to the 70D as having a 70 kWh battery, but then recommends that you charge only to 80 or 90% unless you are going on a long trip. In addition, the battery starts to encounter restrictions in performance when its charge level drops to about 20% (or even before). So the consensus among owners seems to be to maintain the battery between 20 and 80% if you can. This means that the effective useable capacity is 60% of 70 kWh, or 42 kWh. When you combine that practice with the higher consumption in winter, you can find yourself quite restricted. E.g., using my average value of 549.7 Wh/mi and 42 kWh, that implies a driving range of only 76.4 miles. And in fact, my average distance traveled between charges was 70 miles, with 111 miles being the longest I drove between charges in this period. (That 111 mile interval included a pair of trips of 20+ miles, so the energy use per mile was reduced.)

    Obviously, you can obtain much higher practical ranges by charging the battery to 90% or more when you need to, and driving until the battery charge is less than 10% if you are certain of where you can charge. And your range will be higher for longer trips – again, my driving pattern may be on the extreme end of inefficient, short trips, and thus unrepresentative.

    My own conclusions from this exercise are:
    1. Short trips are a huge factor in energy consumption in winter, because of the energy spent to heat the cabin, for each trip no matter how short.
    2. The battery limitations at less than 20% charge (on regenerative braking and preheating), combined with the limitations of cold weather (restricted battery reserve and reduced charging rate) are strong incentives to avoid discharging the battery that much if you can avoid it.
    3. By the same token, if the cold is severe, consider charging to 90% or more to ensure you have the range you need.
    4. The advice to “buy the largest battery you can afford” is even more important for people living or travelling in cold climates.

    What I would like to do is to take some longer trips on a cold day and compare the energy use of the 70D with the data reported by other people for models with the 85 Kwh battery. I will try to do that if time and weather permits and report the results.

    The intent of this post is to inform. This is not a criticism of the car – I love my Model S! But I think it is important for people to understand the facts of cold weather effects on range.

    Side note: Each time I charge, I record the data from the Trips screen for “Since last charge.” I found in doing this analysis that that data is sometimes incorrect. I have seen other posts that noted issues with the Trips screen since the version 7.0 software release so I did not use those data in my analysis.
     
  2. AgentWimplo

    AgentWimplo Member

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    I also have the 70D and live in upstate NY so I experience similar weather...

    The problem with your range assessment is that using your energy consumption for short trips and then just applying that to the range you'd expect is a pretty flawed way to calculate the the rated range you would experience. I take some pretty regular longer trips 30-50 miles and my consumption is no where near 547Wh/mi. Even on some single digit temperature days I experienced what I would consider very reasonable consumption 350-400WH/mi. Once you get beyond the high consumption battery warming phase I've found that the consumption drops back down.

    Just yesterday I left the house at 90% charge, drove Ithaca to Syracuse (50mi) in 20degree weather, parked outside for 4hours, and then drove back home with plenty of range remaining.

    My trip was logged on TeslaLog outside temperature was 10-15 degrees Fahrenheit:
    13:19 - 14:32 - Lake Ave, Ithaca, NY - 60.2Miles 397.5Wh/mi - ODO 4252 [​IMG]
    08:31 - 09:36 - Harborside Dr, Syracuse, NY - 57Miles 357.3Wh/mi - ODO 4192

     
  3. AWDtsla

    AWDtsla Active Member

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    #3 AWDtsla, Feb 16, 2016
    Last edited: Feb 16, 2016
    I agree. Bjorn's data is heavily geared towards very long trips that amortizes the cost of startup over the whole trip. But perhaps instead of saying short trip, the number of stops should be considered. i.e. If you have a schedule like commute to work, then commute to the gym after dinner, you have a 4 stop day. Each stop can eat large amounts of power, i.e. several percent.

    I also plan on about 70-75 miles of real range in the cold despite having a larger battery, but it's not as big as you think, since the comparison is more like 70kWh usable vs 83kWh usable.

    edit - I should add that my fueling costs in the winter are higher in the Tesla than they would be in some of my other gas hungry cars. The only mitigation is free charging at work, but I can't see that party lasting long.
     
  4. svp6

    svp6 Member

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    Also remember Bjorn drives mostly on single lane roads, at traffic speed well below highway level. Increasing speed from 65 to 70 is modestly taxing, but from 70 to 75 mph and above is prohibitive in winter time.
     
  5. AWDtsla

    AWDtsla Active Member

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    I'll take 85, thanks.
     
  6. travwill

    travwill Member

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    Yes, very good observations on the more frequent stops and energy usage. I have the 70D also and it usually hasn't been a problem as don't drive too far. Most days I can still charge to say 50% even and be fine but when I do get around the city, burbs, and stop frequently - definitely 90%, and there have now been a couple times I've gotten home with say 15-20 Rate Miles left and have been a little hesitant in traffic. It does seem that when it is really cold too and you get stuck in some bad winter traffic, going slow, that you'll eat up a ton of miles also. In some just yesterday I had about 90 RM left, but projected stated 10-30 at times, so naturally the Rated drop fast and you start to wonder if you really just have 10 left if traffic doesn't improve (thus turn off heating some, etc. hehehe).

    Still a great model for "city folk" as it is pretty efficient most of the time, and best for warmer climates. I think now looking back, that range is king, and that if 90D was available back then I'd snap it up instead, at the extra cost.

    For now, I'll look forward to that 1?? D future upgrade ;-)
     
  7. PA70D

    PA70D Member

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    In general agree with comments about range and battery degradation in the cold. Have taken a number of trips in temperatures in the high teens and low 20s and have found energy usage around 380 or so at 70 mph after fully warmed up. Happy with this car even with cold weather limits. The main reason for this post is to share a blog which found to be very helpful.

    Cold Weather Driving - Blogs - Tesla Motors Club - Enthusiasts & Owners Forum
     
  8. David29

    David29 Member

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    Thanks! I had not seen that.
    And thanks to the others for their comments. And I certainly agree with AgentWimplo that my experience would be better if I had more long trips in my data. I saw that in the Fall when I took my first long road trip to Maine. And i certainly agree that the big factor is the number of stops and thus how many times the car has to be heated up. But I could only report what I had experienced. I will definitely try to update this post if and when I can take some longer trips, with fewer stops, in the cold.
     
  9. sorka

    sorka Active Member

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    • Something is wrong with your Tesla. I've never seen anywhere near that consumption even in 9F weather in the mountains on snow.
    • Climate doesn't factor into the wh / mile reading you see so you're actually getting even worse range than you think.
    • Why aren't you preheating on shore power so you don't take the hit when you first leave?
    • You're number for rated wh / mile is not correct. If the 70D has the same 3.9 KWh anti brick buffer and 5KWh zero mile buffer as the 85, you're wh / mile to reach rated is 258 wh / mile, not 292.
    • Why not charge to 90% every time? It won't really be worse than 80% *especially* if the battery is cold. What's really bad for the cells is charging to 100% *when* it's warm or hot because the anodes expand from being charged and from being warm, but if the battery is really cold, I'd personally charge to 95% under those conditions and then back off to 90% in the spring, summer, and fall.
    • I agree with your conclusion list at the end of your post :)
     
  10. AWDtsla

    AWDtsla Active Member

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    You thought that about mine too. But I can basically get the car's trip meter to report around the values what evtriplanner predicts givens the speeds and circumstances. Of course the trip meter is flawed and underreporting true usage. You get actual usage via metering. His usage seems completely believable to me.
    wha?
    No he is correct, it's 292. 258 would seem right if all the other specs from Tesla were reliable. But it's ~292 Wh/mi and ~70kWh usable for ~240 rated miles
     
  11. sorka

    sorka Active Member

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    Um no. 292 wh / mile is assuming the ENTIRE 70 kWH capacity can be used for driving which of course it can't. The amount of zero mile buffer and anti bricking buffer could vary a little but not by much.

    Climate control does not factor into the meter nor do lights or the sound system.

    As for evtripplanner.com please post a route and specs that come anywhere near close to the the usage the OP is reporting.
     
  12. MP3Mike

    MP3Mike Active Member

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    Are you sure? I thought all power usage was included regardless of where it goes.
     
  13. AWDtsla

    AWDtsla Active Member

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    It's 292. The energy analyzer says it's 292. As for the capacity, see the other gigantic thread about battery capacity... That's what half the uproar over there is about. Looks like it's probably 74kWh battery with a 4kWh buffer.

    That is a huge problem. Heater draws 6+kW at startup and will continue to use a lot of power even after the cabin is warm. That's basically enough power to propel the car a 20mph constant speed. Lights/sound is nearly nothing.

    I've done it probably literally a thousand times already. Like I/we said above the shorter the trip the more inaccurate it is. If you're claiming climate control isn't included _at all_ in the trip meter, well there's your difference.

    - - - Updated - - -

    *something* is definitely missing. Preconditioning is definitely missing, what else, I don't know. Whatever it is, it's stupid.
     
  14. sorka

    sorka Active Member

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    My commute is 130 miles each way. If I drive with the heater or AC or both on, the wh / mile * miles diverges from the percentage of battery used by the time I get to work or home. If I don't use climate, lights off, stereo off (everything off) the wh / mile * miles nearly matches the percentage drop within a 1/2 KWh i.e. the battery is about 1/2 KW lower than it should be based on the wh / mile usage.

    - - - Updated - - -

    I ask again, can you please post the route and conditions used in evtripplannner that have it predicting anything close to what the OP is seeing?

    - - - Updated - - -

    Which energy analyzer? And do you have a link to the other thread?
     
  15. AWDtsla

    AWDtsla Active Member

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    The energy analyzer in the center console. The line it draws for rated miles is the rated Wh/mi for your car. It's 290 for a 70D.

    Tesla's 85 kWh rating needs an asterisk (up to 81 kWh, with up to ~77 kWh usable))


    I don't see how to post a link to from evtripplanner. But it's trivial. Simply drop the outside temp to 10F, then raise the speed multiplier until the trip time or segment speeds are reasonable. Just plotted one trip 426Wh/mi 70D 466Wh/mi P85D, both with 19" wheels.

    Try boston, ma to bretton woods, nh, 1.2x multiplier (gets you speed of normal traffic), 10F, 70D. 464Wh/mi. In a P85D a whopping 517Wh/mi! If there is snow on the ground you're screwed.
     
  16. Max*

    Max* Autopilot != Autonomous

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    Just wanted to pull this out. I agree. On long trips, in the cold, the 70D does fine (about 320-330wh/mi I've seen). On multiple short trips, with no prewarming, no range mode, I've seen 500-600wh/mi.

    - - - Updated - - -

    I think it's much lower than 20%. I've been down below 20% on pretty much every road trip, and I've never been limited in performance (only when I took the car down to single digit range)

    - - - Updated - - -

    This was discussed in several other threads. The 70D is around 288wh/mi rated, maybe 292wh/mi. But it's not 258wh/mi. Look especially at WK's thread comparing the 60 (which has more than 60kwh) and the 85D (which has less than 85kwh).

    The 70D (I speculate, based on what I've seen) is similar to the 60, in the sense that it's under-rated to sell more 85Ds.

    - - - Updated - - -


    This graph:

    20160115_133601.jpg

    From a 70D. Rated is right below 300wh/mi. From my experiments I think it's about 288wh/mi, but 292wh/mi might be right... I don't recall the exact number.

    If you assume that it's 252wh/mi, that would mean the rated line would have to be well below the 300wh/mi line (look at the 328wh/mi line, it's 28wh/mi above the thin gray 300wh/mi. Now if you take that distance and go down 300-28 = 272wh/mi. But it's clear that the solid gray line (rated) is MUCH closer to 300 than the distance between 300 and the average of 328).
     
  17. AWDtsla

    AWDtsla Active Member

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    They're all within about 1%, close enough for estimates. Someone with a CAN logger can probably get very precise values.
     
  18. sorka

    sorka Active Member

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    Ah, the one built into the car. Mine shows 300. So the 70D shows 292 on that line? Did the folks in that thread conclude that this must be proof that the usable capacity is 70 kWH? Did anyone actually drive from a full change to some really low charge like 10% and extrapolate the kWH by percent and show that at 10% battery they'd used 63 kWH? If so, I think I'd take that as proof that there is 70 kWH usable and that the battery must be larger than that although if that's the case they probably left nothing for the 0 mile buffer and lowered the anti bricking buffer to a few kWH. If this was all analyzed to death in the thread below, I apologize for missing the party :)




    I used a multiplier of 1.1 since 1.2 is excessively speeding. I also used a round trip since your example included a significant elevation climb. By only exceeding the speed limit by 10% which most drivers don't exceed and keeping the playing field equal (so to speak) the same example produces 405 wh / mile which seems like the actual worst case usage for the example you posted.

    So I stand by my original assertion that there is a problem with the OPs car. Perhaps alignment?
     
  19. AWDtsla

    AWDtsla Active Member

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    It varies widely by road. You have to either look at the segment mph numbers, or do what I do - do the trip, make the speed multiplier match exactly the trip duration.

    The trip I told you about has a very long stretch on a 70mph road, btw. the multiplier I gave you only gets that to 78 mph, not even the minimum customary 10 over that everyone drives. However around here 80 in 65 is usually acceptable. If I drove that route normally, the speed multiplier would have been higher.

    You're totally missing the part about short trips an warm-up costs, and that I've said repeatedly that evtriplanner does not take warm-up costs into account.

    I just did a 16 hour usage analysis on my car.. I believe the dash is in the 500Wh/mi range. My calculated rate is 936 Wh/mi. So again, his usage is not out of line.
     
  20. Max*

    Max* Autopilot != Autonomous

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    There is no 0 mile buffer on any Tesla. It's been debunked many times over. There is an anti-bricking buffer though.

    To answer your question, no, that thread didn't have a 70D tested. It had a 60 test (which had 61.1kwh with the anti-bricking buffer) and the 85D tested which only had (80.7kwh with the anti-bricking buffer).

    So again, if the 70D is anything like the 60, and I speculate that it is, the math for the rated wh/mi you used is incorrect. And it's much closer to 290wh/mi than it is to 250wh/mi.

    - - - Updated - - -

    A speed multiplied of 1.1 is not exceeding the speed limit by 10%. If you look at the details tab, a 1.1x multiplier is going faster than the average speed on the road by 10%. Not speed limit. Big difference here.
     

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