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Survey Results: Rated Range

Discussion in 'Model S: Battery & Charging' started by Owner, Jul 30, 2013.

  1. Owner

    Owner Active Member

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    Thanks to the 62 people who filled out my survey trying to understand Rated Range. The long detailed analysis is available here on my blog.

    For purpose of discussion, the executive summary is the following:

    Rated Range Varies for the Majority of Cars in the Following Bands:

    175-195 for 60kWh Batteries
    220-245 for 85kWh Batteries

    The rated range appears to have no correlation between energy used over long periods of travel.
    The rated range appears to have no correlation between miles driven. Since the cars are so new there is unlikely to be much battery degradation yet.

    I have included at the end of this post one of the four charts I created. The 60kWh battery range vs. energy (Wh / mile) has fewer outliers. The 60kWh data set is a third of the size of the 85kWh data set but shows the lack of correlation in a clear manner.

    I think this survey almost asks more questions than it answered. There is clearly not a clear correlation between long term driving habits and rated range. Perhaps immediate short term driving habits? Perhaps the car simply cannot measure the amount of energy in the battery very accurately? How accurate, reliable and useful is this rated range number? Why is there so much variation in the rated range number in the Model S?

    What I would personally like to see is an accurate consisted rated range that I could understand and also a simple energy measurement. I would like to see a gauge that simply said 55kWh left in my battery. I would find this more straightforward. I can do the simple math in my head to convert that to "can I drive to X without recharging"

    I am also wondering if part of the problem with giving these accurate numbers is that historically cars do not give you accurate measurements of remaining fuel. All of the cars I have owned have had crude analog gauges or digital readouts that were stepped scales and not a simple readout "12.1" gallons left.

    I am looking forward to any comments on this survey and if there are any suggestions on other things to look at.


    ratedrangevsenergy60.jpg
     
  2. MichaelS

    MichaelS Member

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    Location:
    Hayward CA
    Hi,
    I'd like to add my data.
    MS 60
    Miles on car 7239
    Lifetime Average 7212 miles, 2059.5 kWh used, 286 Wh/mi.

    One comment I'd like to make. In looking at the spread of range available between the different cars, my experience with other EV's and their BMS systems, I think the level of discharge the car has experienced could make a difference in the rated range.

    When the car is new, there is an approximate value of battery capacity programmed into the BMS as default. The BMS monitors amp hours used and voltage to measure the capacity remaining.

    If the battery has been deeply discharged, I believe the BMS has a better idea of what the actual capacity is, and as such adjusts the range.

    It would be interesting to find out how far people have discharged their cars and plot that against rated range.

    I remember my Leaf which I ran into lower than zero several times, would give me more indicated range afterwards, sometimes as high as 124 miles after a 100% charge.

    I have never driven my car below 40 miles range, So I have never stretched the pack so to speak.
     
  3. Owner

    Owner Active Member

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    The actual survey is here Rated Range and Average Energy Tesla Model S Survey. <not sure if i am going to update any reports though> You didn't include a rated range number.

    286 Wh/mile is quite low. Mine is a lot higher.

    I think I only have driven my car near 50 miles range left and generally rarely get much below 1/3 empty, and I also have a rated range on the low side.
     
  4. MichaelS

    MichaelS Member

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    I knew I forgot to include rated miles.

    Here is the data from TeslTime after just finishing charging:

    "charging_state": "Complete",
    "charge_limit_soc": 90,
    "charge_limit_soc_std": 90,
    "charge_limit_soc_min": 50,
    "charge_limit_soc_max": 100,
    "charge_to_max_range": false,
    "battery_heater_on": null,
    "not_enough_power_to_heat": false,
    "max_range_charge_counter": 0,
    "fast_charger_present": false,
    "battery_range": 180.33,
    "est_battery_range": 211.24,
    "ideal_battery_range": 208.08,
    "battery_level": 90,
    "battery_current": -0.1,

    What was interesting was that when there were 2 minutes left it was indicating 182 then as soon as charging stopped, it dropped to 180 miles.
     
  5. lloyds

    lloyds Member

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    Thanks for setting this up. Very helpful in seeing where I stand
     
  6. SFOTurtle

    SFOTurtle Active Member

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    I just made a similar observation on another thread about reductions in rated miles. Mine seems to do this quite a bit. Today I did a range charge as a first attempt to re-balance the battery after 6 mos and 7200 miles and showed 204 rated range just before charging stopped but then dropped to 201 right after.
     
  7. MichaelS

    MichaelS Member

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    This could be because the BMS is calculating the range at the peak charge voltage, which of course will drop as soon as the charger shuts off. There is no tapering of the charge current at the end if you don't do a range charge.
     
  8. Owner

    Owner Active Member

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    Thanks Lloyds, I think this is probably the useful outcome of the survey. There is a significant variation of rated range but I wouldn't be worried about a car within that range.

     

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