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Texas and battery life

Discussion in 'Texas' started by CGW, Sep 8, 2015.

  1. CGW

    CGW Member

    Joined:
    Jun 13, 2015
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    Location:
    Austin, Texas
    Hi
    I park my beautiful Model S outside each day when I go to work in Austin. These days at 5:30 or 6PM the phone app often reports an internal temperature greater than 110 degrees F. I have seen 126 degrees F. I found the scary clip below on a site called "Battery University". It relates to lithium ion batteries. I wonder if it s really true that the hot Texas summer is damaging my battery and reducing its life by 50%???? Do I need to leave my Model S in an air conditioned garage and ride a bike to work?? That would surely damage me! Are there any electrochemists or battery buffs out there who can assuage my fears?? :confused:

    All batteries achieve optimum service life if used at 20°C (68°F) or slightly below. If, for example, a battery operates at 30°C (86°F) instead of a more moderate room temperature, the cycle life is reduced by 20 percent. At 40°C (104°F), the loss jumps to a whopping 40 percent, and if charged and discharged at 45°C (113°F), the cycle life is only half of what can be expected if used at 20°C (68°F). (See also BU-808: How to Prolong Lithium-based Batteries.)

    CGW
     
  2. JMG

    JMG Member

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    Location:
    NE Texas
    You might get more response to this thread in the battery and charging section, and have you done a search on this site for the same topic? I'm sure it's been covered before.

    The battery monitors and helps cool itself. It supposed to be one of the most advanced batteries in the world, so I wouldn't lose too much sleep over it. I have, however, heard that you don't want to expose it to really high temperatures when its at a very high state of charge. So, I would not park it outside in 100 degree weather with a state of charge of 95% or so.

    Do a search and I bet you find some good info.
     
  3. jerry33

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

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    The graph, which I can't find right now, for the Roadster shows that location vs. degradation is random. I don't believe there is a chart like this yet for the Model S. The liquid cooled batteries are reasonably protected from the heat so it's not really an issue the way it is in some other EVs. What I do is set the charging to start so that it will be finished by the time I start to drive. For me this is 02:30. That lets the car stay at a lower SOC for the majority of the day.
     
  4. LMB

    LMB Member

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    (LMB spouse)

    I find that the internal temperature report can read very high if the car has been parked for a while. I think the sensor location may not sample the cabin temperature very accurately if the fan is off.
     
  5. apacheguy

    apacheguy Sig 255, VIN 320

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    What we need here is a reading from one of the pack sensors. It has multiple. The trouble is that Tesla does not expose their output to the user.
     
  6. Joel

    Joel Active Member

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    Location:
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    Tesla uses thermal battery management to cool the battery.

    Watch this to assuage your fears: Why do Li-ion Batteries die ? and how to improve the situation? - YouTube
     
  7. stopcrazypp

    stopcrazypp Well-Known Member

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    Right, the pack temp and the interior temp may be very different. The interior temp rises rapidly because of the sun heating the air inside through the windows.

    The largest source of heat for the pack would be the ground emitting heat that it absorbed.
     
  8. apacheguy

    apacheguy Sig 255, VIN 320

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    Depends on how well insulated it is from the main cabin. This NREL report points to solar loading on the cabin as big factor in heat stress. Granted, that is for a Prius, but still.

    http://www.nrel.gov/docs/fy12osti/53817.pdf (Fig 3)
     
  9. stopcrazypp

    stopcrazypp Well-Known Member

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    I remember for the Leaf, I read that heat from the asphalt was the biggest source, so I guess given the Model S battery is similarly floor mounted it would be similar.
     

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