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Daily Rated charge question

Discussion in 'Model S' started by skboston, Dec 5, 2014.

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  1. skboston

    skboston Member

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    I have a question to all of you that charge your car to it's daily charge level at 90%, I've experienced loss of charge over the last couple of months and would like to get a feedback from you on what's the Rated mileage you get when charging is complete?

    I had my car serviced the other day and the Tesla loaner they provided me charged to 241 miles with Vin #37xxx and about 5500 miles on it.

    My car is #13xxx and has close to 14000 miles on it. The loaner rated mileage immediately drew my attention, as my car would charge to levels between 223 and 230 but never over that. I've done a "tuning" full charge as suggested by Tesla SC a month ago, but no significant difference.

    Here is what Tesla said when I brought the complaint again when my car was in the shop (direct quote from the service invoice):


    "Concern: Customer states daily rated ranger is between 223-229, loaner car is 241. Please advise.


    Corrections: Battery Assembly General Diagnosis


    Overall battery health appears good, there is some diminished capacity over time and environmental conditions will have an effect on overall capacity."

    I live in the Boston area, so I'd like to know what these environmental conditions are and I find it strange to have lost 11+ miles of Rated charge for just 14000 miles on the car. If we assume 300wh/m is the rated formula (for easier math), it's a loss of 3-4kW in the pack, which is significant for 1 year old vehicle.

    What are your experiences and do you think that's normal wear and tear on the battery? I love the car and I'm not concerned so much at the moment, but in 6 months or year, if this continues then I'll have a serious issue on my hands.
     
  2. efusco

    efusco Moderator - Model S & X forums

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    My 90% rated has slowly trended downward. I'm at 44,000 miles and typically see 231-234 miles rated in the morning when I get to my car. Warmer weather it was a tad higher I think.
    If a run the battery low on a long trip then do a full range charge I'll typically see a transient bump in my 90% rated to around the 235-238 range.

    Yours does seem a bit low to me, but it sort of depends when you're charging, how cold it is, and how long you wait after charging to see the level. In other words, are you charging immediately when you plug in then not looking at the rated range until morning? If so, you'd expect some vampire drain over night, particularly if it's fairly cool outside. If 223 is the finished charging rate checked almost immediately, that seems darn low to me for a car with 14,000 miles. But probably not outside of spec.
     
  3. JohnQ

    JohnQ Active Member

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    I'm an Apr 2013 delivery with 25k miles. My 90% charge is 223 every morning (per app notification). Haven't discussed with anyone at Tesla as it could be for a myriad of reasons. 'A' pack battery if that makes any difference. Doesn't matter much if I've done range charge and depleted or not.
     
  4. skboston

    skboston Member

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    Those are all charging levels no more than an hour after car finishes charging, I plug it in at night and I'm well aware of the vampire drains with the cold weather, I usually loose 3-4 miles overnight, which is normal and it does get cold here, usually below 30F at night now.

    It bothers me that ~3-4kW is considered within spec and normal degradation. I've never seen numbers above 230 miles even during the summer, I guess I'm hoping this trend doesn't continue as it is now, if you get 235-238 at 44000 miles, with my rate of loss, I might be in the low 200's when I hit that many miles, which would be in a 1-1.5 years from now with my driving.
     
  5. Todd Burch

    Todd Burch Voltage makes me tingle.

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    My car is less than 1.5 months old, about 3,300 miles, and I show 239 for 90%...so the older and higher mileage loaner you had shows higher than mine. I think that partly goes to show that a lot of this is a calculation issue, not a true battery issue.
     
  6. skboston

    skboston Member

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    It's quite possible to be a calculation issue, but this much of a difference?

    I guess the only way to find out is to do a Range charge and let the battery hit 0, when I'm near my house and see the kW used, rather than going by the mileage. I'd wait until the spring for that, when it warms up around here :)
     
  7. scaesare

    scaesare Well-Known Member

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    I get about 226-227 miles @ 90% charge. This is a May '13 car with ~34K miles on it currently. I only charge to 90% on weekends.

    Have you read THIS?
     
  8. mknox

    mknox Well-Known Member

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    I had been charging to about 70% daily and returning at night at about 30%. I noticed my numbers were dropping, and someone suggested repeated charging to 90%. When I started charging to 90% I was getting about 218 Rated Miles at 90% and now seem to have plateaued at 221 Rated Miles.

    So, I have about 38,000 miles and 18 months of use on the car and get 221 Rated Miles at 90%. This is with an "A" pack battery.
     
  9. AmpedRealtor

    AmpedRealtor Well-Known Member

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    #9 AmpedRealtor, Dec 5, 2014
    Last edited: Dec 5, 2014
    What is your IDEAL range right after completing a 90% charge?

    Ideal range is a much better indication of potential battery degradation because the consensus appears to be that the ideal range algorithm has not changed and simply performs a straight line calculation, while the rated range algorithm has been tweaked several times and takes more factors into consideration. Also, is your range mode turned on or off? If range mode is turned on, it will result in your range estimate going up by a couple of miles.

    Case in point: my rated range has dropped from 265 miles to 257 miles at 100% charge, which is a drop of 8 miles in 15 months and 17,000 miles, while my ideal range estimate has dropped only 3 miles in the same time, from 301 miles at 100% charge to 298 miles. As you can see from my particular case, the two figures don't correlate.

    Rated range appears to drop based upon approximately 285 Wh/mi while ideal range drops at a rate of 250 Wh/mi. If I trust rated range, I've lost approximately 2.0-2.3 kWh. If I trust ideal range, I've only lost about 0.75 kWh. The discrepancy between the two is a factor of almost 3x. Something isn't right with the rated range calculation, in my opinion, and it is therefore exaggerating the appearance of battery degradation.
     
  10. skboston

    skboston Member

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    Ok, so I did as you suggested AR and charged the car to 90% and it shows 265 ideal miles vs 229 Rated ones. I haven't done a 100% charge in more than a month, so can't tell the numbers, but will do one tomorrow morning.

    My range mode is always OFF, I've only used it a couple of times.
     
  11. David99

    David99 Active Member

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    As others have said, the rated range number is a mathematical model, not a 100% accurate measurement of the actual battery capacity. Tesla officially said that the method of how rated rage is calculated has changed over time. So it can't be directly compared to what your car showed half a year ago.

    It will also factor in temperature. So as it gets cooler the range will be less because a cooler batter can't deliver the same capacity as a warm one. The ideal operating temperature is well above 100 degree Fahrenheit.

    The only way to figure out how much capacity is in a battery is to charge it to 100% and then discharge it to (almost) zero. Everything else is just an educated guess.

    Coming back to the daily charging level. 90% is fine if you end up with about 20% left in the battery at the end of the day. If you drive less in one day, only charge as much as you need plus 20%/50 rated miles.
     
  12. AmpedRealtor

    AmpedRealtor Well-Known Member

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    Extrapolating from the 90% charge at 265 ideal miles would get you about 294 ideal miles at 100%. If your 100% charge validates this assumption, then I think your range loss is significantly less than originally thought.
     
  13. aprm1024

    aprm1024 Member

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    I've been seeing something similar, my car is a MS 75D and when first delivered 90% charge equaled 227 miles, lately I see 226 or 225. I wonder if the calculation is based on the past 30 miles of driving
     
  14. David99

    David99 Active Member

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    No, the rated range is a fixed number based on the remaining energy left in the battery divided by the energy consumption established in the EPA test. That's why it is called 'rated range'. It's based on the EPA rating and does not ajust to driving style. 'Ideal miles' also does not adjust with driving style. It's just a number based on a more optimistic energy consumption.

    To get an estimate based on your driving style/conditions, you can look at the consumption in the energy graph and get an average over the last 5, 15 and 30 miles. On the right you will see what range you will get if you keep driving like you have been in the last 5, 15 or 30 miles.
     
  15. aprm1024

    aprm1024 Member

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    Do you know why the mileage would drop from 227 to 226/225?
     
  16. gsteele

    gsteele Member

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    Two causes. One: the first year is the worst for battery degradation, so you lose a few miles due to that. Look up one of the many threads on that topic. Two: this time of year the weather is cooling off. This affects the voltage coming out of the cells a little. My car drops 3 or 4 miles of rated range in the winter, then it goes back up in the summer.
     
  17. David99

    David99 Active Member

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    The battery loses some capacity over time. That's happening to all batteries. Also keep in mind a 1-2 mile difference is less than 1%. Measuring the capacity of a battery can only be done indirectly so the BMS (battery management system) uses a lot of secondary data to make the best guess. Tesla does a great job, but the accuracy has limits thus a variation of less than 1% might as well mean nothing else other than just being at the limit of how accurate the entire system is.
     

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