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Battery thermal management

Discussion in 'Technical' started by apacheguy, Jun 19, 2016.

  1. apacheguy

    apacheguy Sig 255, VIN 320

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    So the past couple days have been pretty warm here in SoCal and my Model S has been conditioning the battery. I hear the fans spin up and this is further confirmed by my diagnostic logs. The DC/DC converter outputs anywhere between 300-600 watts compared to the usual 50 watts while the car is in the wake cycle.

    However, what does not make sense is that the battery temperature actually INCREASES during thermal management. It went up from 35.7 to 38.5 C in just over two hours. What's going on?
     
  2. scaesare

    scaesare Active Member

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    It kept it from going up by 10 degrees instead?
     
    • Informative x 3
  3. apacheguy

    apacheguy Sig 255, VIN 320

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    I guess that's possible. I'm just surprised at how quickly the battery heats up. Everyone has assumed that the battery is such a large thermal mass that it takes much longer to heat up. What I'm seeing indicates that it very closely mimics ambient temperature.
     
  4. apacheguy

    apacheguy Sig 255, VIN 320

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    So I have enough evidence to say this is not what's going on. It appears that Tesla updated the thermal controller firmware to dynamically adjust cooling set points. When driving, the cooling target is lower than when parked. Today we had a high of 95 F. The pack reached 37 C and cooling was not occurring. This is on 2.28.60
     
  5. Electric700

    Electric700 Member

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    Apacheguy, you said earlier that the temperature increased from 35.7 C to 38.5 C, and just now reported that cooling does not occur at 37 C (which is in between). So, what's the cooling start threshold? Also, can you monitor to see what happens when you turn on the AC from the app and leave it on for 15 minutes? Before you turn it on, see what the battery temperature is, then after 15 minutes check the temperature again.
     
  6. bhzmark

    bhzmark Active Member

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    How are you monitoring battery temperature?
     
  7. apacheguy

    apacheguy Sig 255, VIN 320

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    Will try to do more tests. I monitor using a raspberry pi with a CAN shield that is connected to my wifi network.
     

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