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Extra miles immediately after max range charging or topping off

Discussion in 'Model S: Battery & Charging' started by balefire, Dec 26, 2015.

  1. balefire

    balefire Member

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    I've noticed this before but never measured.
    I max charged my car at a SC. I spent an additional 15 to 20 min or so hooked up after my max range was achieved and the car said it was still charging very slowly without increasing my range..

    After leaving, I was able to drive 10 miles before my range dropped 1 mile. Anyone else notice this driving immediately after full charge?
     
  2. scaesare

    scaesare Active Member

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    Not terribly uncommon to have additional range beyond what's displayed... particularly after charging to a higher level than "normal", such as a range charge.

    Being able to go 10 miles before the first mile clicks off is a bit more than typical however... usually it's something like 3-5 that I've seen reported, and is what I experience as well.
     
  3. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

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    I've had various numbers, some higher than ten (though I haven't kept any record of them)
     
  4. apacheguy

    apacheguy Sig 255, VIN 320

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    My range counter begins ticking as soon as I leave the driveway. I typically charge to 80%. I allow all my 100% charges to complete, but have never, ever experienced the OPs symptom. Wonder why.
     
  5. HankLloydRight

    HankLloydRight Fluxing

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    This for me.. About 5 miles.
     
  6. taurusking

    taurusking Member

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    For me this morning after range charging was 6 miles.

    - - - Updated - - -

    What you are referring is balancing of pack ....search the forum for pack balancing or balancing the pack .....and you will find ton of info on that.

    BTW What was your miles after range charge?
     
  7. apacheguy

    apacheguy Sig 255, VIN 320

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    Actually, balancing occurs regardless of whether the car is charging or not. In many cases, balancing will take on order several hours. The final hour on a 100% charge where the current rapidly drops is not enough to complete balancing on its own; what is being observed here is instead that the BMS is carefully regulating voltages so as not to exceed a threshold.
     
  8. green1

    green1 Active Member

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    I have had this happen on range charges, I think it's more "calibrating", it's very difficult to calculate how full a battery is, and the only way to really do so is to charge it to full. So when you charge to 90% all the time (or whatever percentage), over time the car loses track of exactly where "full" really is. When you then charge to 100%, it can take a bit to calibrate where that full mark is, so it takes a bit of time after you get there for it to really settle on where "full" was and to know how much energy in total is in the pack. Then you start to drive, but the voltage doesn't necessarily immediately start to drop, so the car doesn't show you using range.

    Basically, knowing how full a gas tank is is easy, you just put a float in it and see how low it sits. Batteries are much harder, you have to calculate exactly how much current has flowed, where the voltages sit, check rate of discharge, and know where both the full and empty marks are while they change over time. I'm actually always amazed at how well Tesla is able to do at guessing how much range you have in there.
     
  9. balefire

    balefire Member

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    My miles after 100% range charge was 251.
    I have 35k on my car.
    Yes I have some degradation, but I'm not freaking out about it because with SC readily available, it is not as big a deal as it used to be.

    Interestingly, it seems that I get more "extra" miles when I
    a) SC 100% charge or HPWC @ 80 amps
    b) leave 15-20 min after max range achieved

    I wonder if the battery likes to be "hot"? I know that was true when I used to race RC cars. I would purposely top off the battery to get it warm for extra performance during races. I'm curious if charging at high amps to max 100% range does the same for our Tesla...

    when I do slow charging in attempts to rebalance the pack or if i leave even 40 min after charge, the extra mile effect disappears or is minimal.
     
  10. scaesare

    scaesare Active Member

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    There is no real way to instantaneously measure the amount of total energy available within the pack at rest. Charging completely, then discharging completely, while tracking energy used is the only practical way to do it.

    The only actual metric available via direct measurement while a battery is stationary is voltage. Based on a model of the battery, and other factors (ambient temp being a big one, age being another), you can infer what amount energy is in the pack.

    Once you start driving, if the actual measured voltage drops at a different rate than the model predicted, then you can end up with either greater or fewer range miles clicking off as physical miles are driven. This tends to be more noticeable at the pack extremes (closer to fully charged or discharged), as the voltage-to-SoC curve is less linear in those regions.

    This also is part of the reason why your rated range can go UP after a charge completes. the voltage can float up due to temp rise, etc... and the model recalculates that there is now more energy available.
     

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