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What's going on with my car's range?

Discussion in 'Model S: Battery & Charging' started by markb1, Mar 10, 2015.

  1. markb1

    markb1 Active Member

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    #1 markb1, Mar 10, 2015
    Last edited: Mar 11, 2015
    So, recently, the remaining range on my car has been decreasing faster than seems appropriate. For instance, last night, my car charged to 151 rated miles and 172 ideal miles. (I have a 60kWh pack, and the charge limit is set to 80%.) By the time I starting driving it this morning, the range was down to 148/169, so I'll use that as the starting point.

    I drove only 35.5 miles today, using 16.9 kWh, for and average of 464 Wh/mile. (All three of those numbers are according to the "since last charge" meter.) My range was down to 77/88, for a decrease of 74/81 miles.

    By my calculations, using 16.9 kWh and the miles from the range meter, that makes a rated mile 238 Wh, and an ideal mile 209 Wh. Those seem very low, and the miles consumed seems very high. I thought a rated mile was based on EPA range, which makes it around 288 Wh/mile for the 60 kWh pack. At 288 Wh/mile, and 16.9 kWh, I should have only consumed 59 rated miles.

    Is it just calculating range incorrectly, or is there something wrong with my battery pack?

    Thanks.
     
  2. Thread Summary

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    #2 Thread Summary, Mar 10, 2015
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    Date Rated Range Consumed Energy Consumed (based on 288 Wh/mi) Energy Consumed (trip meter) % Difference
    3/10/2015 71 20.4 16.9 21%
    3/11/2015 45 13.0 11.1 17%
    3/12/2015 64 18.4 15.4 19%
    3/13/2015 20 5.8 4.4 32%
    3/14/2015 11 3.2 3.2 0%
    19 5.5 5.0 9%
    24 6.9 6.3 10%
    3/15/2015 40 11.5 11.4 1%
    20 5.8 5.3 9%
    17 4.9 4.3 14%
    3/16/2015 51 14.7 11.2 31% 5 miles lost while parked! Not included in calculation.
     
  3. Mario Kadastik

    Mario Kadastik Active Member

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    How was the weather? Did you pre-heat the pack on wall power? There are many questions as such since it seems that Tesla no longer accounts climate and heating usage inside those Wh used in full. I know it from the fact that when last summer I sat in the car waiting for a race checkpoint opportunity for one full hour at +32C with cooling blasting to keep the car at 20C I didn't see anything added to either the Wh/km chart nor to the used kWh when I started driving. There was no spike, there was no jump in kWh or Wh/km.

    Having said that, the 464Wh/km is high and points to high level of pack heating probably and would likely mean you also had heating running in the car. Consuming 70 miles for 35 miles range is basically double usage so if pack heating is accounted for and that explains the 464Wh/km, then the rest of about 140Wh/km could be heating of cabin (including pre-heating). That btw doesn't show up as kWh spent so if you drive with heating on then you'll notice you won't be using the full kWh when you've hit 0 range as some of it went to heating and wasn't accounted for. I don't know how long you used the car for, but an estimate of consuming about a third of the consumed kWh for heating (to compensate for the ~140Wh/km) would be about 5-6kWh. That is not that much. When I've measured the car pre-heating the heating runs at about 6-10kW, when in operation I'd estimate it uses only part of that 2-3kW meaning that probably pre-heating for 30 minutes total + 1h of driving with heating would account for the rest of your missing kWh...
     
  4. dsm363

    dsm363 Roadster + Sig Model S

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    Mario is right. Definitely preheat the car for 30+ min before taking off while plugged in. Could also consider changing to 90% if your range is getting low enough on a normal day that it doesn't leave much buffer.
     
  5. Mnlevin

    Mnlevin Member

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    We have a MS 60, and have always charged to 90% every night. Our car has almost 50k miles, and is almost 2 years old and still charges to between 177-179 at 90%. It will drop quicker if cold outside, we don't have that problem in S Fla. don't think you have a problem
     
  6. markb1

    markb1 Active Member

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    I'm in San Diego. The temperature range that day was 49-68, per Wunderground, and the low was probably closer to 60 in my garage, maybe even higher. Is preheating really necessary at those temperatures? If energy was going into heating the battery, is that accounted for in the trip meter?

    It seems like there must be a lot of energy going somewhere other than to drive the motor, but where?
     
  7. Mnlevin

    Mnlevin Member

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    My guess is the number Wh/mile is what is killing the numbers. And what I have found that effects that number the most is accelerating from a stop. If you have a heavy foot, you will keep that number up there and that will kill the range. Just try a little less acceleration and you may see a big difference. IF that doesn't help, then call your service rep.
     
  8. markb1

    markb1 Active Member

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    I don't think that's it. I mean, yes, I do have a heavy foot, and the 464 number seems about right. But my rated range went down by more than double my actual miles, and 464 is only about 60% more than what I think a rated mile is. It's like my energy consumption is significantly higher than the 464 Wh/mile that the car reports.
     
  9. David99

    David99 Active Member

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    I have a similar experience. I drive exactly at the rated miles level as it shows in the energy graph (which is at 300 Wh/m) yet I never ever get the range that it initially says. In other words even driving at the rated range energy usage, it always ends up lower.

    There are a few possible explanations. The rated range is only driving, not standing and idling. The Model S does not account for energy used while the car is standing in the trip meter. It will of course show up as a lower range on the battery level, but the energy usage in the trip meter is not counting it. So the energy usage looks lower than it really is when there are many stops.

    Temperature change can 'eat' energy. When the battery gets cold, less energy is available. Energy usage won't show that either.
     
  10. Alysashley79

    Alysashley79 Member

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    Do you have your temperature set to predictable? I've noticed my car will try to heat or cool itself at odd times which won't account for miles just idling.

    Ive got got a very heavy foot on my P85 and have been known to hit high speeds but I've never seen my Wh/mi above 400 average. Usually it's around 350 and that's with me climbing over 1500' twice in my day. I'd say your loss is the extremely heavy foot...they base their miles at 300 Wh/mo.
     
  11. markb1

    markb1 Active Member

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    I'm not sure what it means to have the temperature set to predictable. But I would think the HVAC system wouldn't have to work very hard here in the mild climate of San Diego

    My high Wh/mi is probably a combination of my heavy foot and my commute, which is on surface streets, and contains lots of stops and starts. But like I've said, my concern is the not the Wh/mi that the car is reporting. It's the range consumed that seems to be in excess of that energy. I would presumably have had to consume much more than 464 Wh/mi to for my rated range to go down twice as fast as the actual miles I drove. I don't expect to be getting rated range the way I drive; I just expect the range consumption to match the energy use reported, or to understand where the rest of the energy is going.
     
  12. Alysashley79

    Alysashley79 Member

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    Predictable...maybe the wrong wording. Shoot. But there's a setting on the car that monitors when you leave in the am and then go home at night and it'll turn on your hvac to either warm or cool your car for you. My car one day had the AC on for an hour at 10pm at night. And it was 38 outside. Not sure what that was about. But am wondering if that could be why you lost some range of the car was taking its sweet time pre warming or cooking for you during the day?
     
  13. markb1

    markb1 Active Member

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    Oh, I see now. I have that feature off, so it should only be running the HVAC when I'm in the car.
     
  14. kennybobby

    kennybobby Member

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    #14 kennybobby, Mar 12, 2015
    Last edited: Mar 12, 2015
    Do you have a screen shot of the energy consumption chart for the last 15 or 30 miles--do you have large peaks during the acceleration portions with the heavy foot?

    Your energy usage and the reported range miles is nearly right on track. You started at 148 rated * 288 = 42.6 kwh pack available (80% charge). You used 16.9 kwh over 35.5 miles (476 Wh/mile), which left you with 25.7 kwh that is nearly equal to 77 rated *288 = 22.2 kwh, a difference of only 3 kwh.

    A 0-60 acceleration in 4 seconds is about 5400 Wh/mile, and in 10 seconds is about 2200 Wh/mile. Big loads pulling lots of amps will obviously reduce the apparent remaining capacity of a battery pack faster than you might realize--your "pack" size is smaller the faster you draw down.
     
  15. markb1

    markb1 Active Member

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    This is the heart of it. (My driving style really isn't what this is about. That should already be reflected in the trip meter. But if you have reason to think that's not reflected in the trip meter, I'm all ears.)

    3 kWh is still quite a lot, though. (3.5 kWh by my math: 288 Wh/mi * 71 mi = 28.4 kWh. 28.4 kWh - 16.9 kWh = 3.5 kWh.) That's 18-21% on top of 16.9 kWh, depending on whose math we use. Is that normal?

    I wish I had thought to check to how much energy had been used to recharge the battery the next morning. I'm going to try to start keeping track of that.
     
  16. kennybobby

    kennybobby Member

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    The extra 3 to 3.5 kwh may be part of the margin held for reserve (brick prevention). 80% of 60kwh is 48 kwh, whereas the 151 or 148 rated after 80% charge *288 is about 43 kwh, so there is about 5 kwh of difference right off the top.

    The cells contain a certain amount of energy for a given charge, and the useful amount of energy that you can pull decreases at higher current draw (the Peukert Effect, Peukert's law - Wikipedia, the free encyclopedia). What you are seeing appears normal and expected in my opinion based upon the little bit of mathturbation of the numbers.

    If possible try to find a screen that will give you real engineering data such as volts and amps at a given % rather than some secondary calculatus such as rated or ideal miles. The whole idea of miles is like counting the number of bars and turtles on a Leaf.

    Drive it like you stole it and enjoy--get that big ol EV grin!
     
  17. Kipernicus

    Kipernicus Model S Res#P1440

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    That does sound excessive, Mark. Did it happen again today?
     
  18. apacheguy

    apacheguy Sig 255, VIN 320

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    If only we had access to the diagnostic screens

    @mark - if you suspect something wrong with the battery pack then the symptoms would likely include rapid loss of range at a given percentage. ken830 had this issue with his 85 kWh A pack - failed module I believe.
     
  19. markb1

    markb1 Active Member

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    What's the symptom? Range decreases at a normal rate, and then there's a sudden drop at a certain state of charge?

    - - - Updated - - -

    Last two days:

















    Rated Range Consumed Energy Consumed (based on 288 Wh/mi) Energy Consumed (trip meter) % Difference
    45 13.0 11.1 17%
    64 18.4 15.4 19%
    I did check the charge screen this morning, and I saw it added 13 kWh overnight, which matches my calculation based on rated miles for yesterday.

    - - - Updated - - -

    The other thing is that it seems like it started happening recently, but I don't have the records to know for sure.
     
  20. markb1

    markb1 Active Member

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    I'm now keeping track of my observations in the thread summary (second post of this thread).
     

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