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HVAC Fan Runs While Charging

Discussion in 'Model S: Battery & Charging' started by gavine, Dec 6, 2014.

  1. gavine

    gavine Petrol Head turned EV Enthusiast

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    I charge in my garage at 40amps via NEMA 14-50, usually at night while sleeping. A few weeks ago, I charged during the day and noticed that the HVAC fan was running. I didn't think too much of it until the same thing happened today. Now I'm wondering if this happens every night as well.

    Is is it normal for this fan to run while charging?

    if I open the door, the fan stops. I tried the app and it doesn't show the HVAC as running. I know it's the HVAC fan because I can feel air coming out through the door handles.
     
  2. David99

    David99 Active Member

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    Yes I noticed that, too. My understanding is that the charger unit itself creates about 1 kW of heat and it's liquid cooled. So the car has to run the coolant pump and eventually also the fan on the heat exchangers. Why it would turn off when you open the door is odd, but I have noticed the same thing with my car. I just trust Tesla on doing the right thing to keep the car and battery at the right temperature.

    BTW I also noticed when my car is not charging but plugged in, it often turns on the coolant pump and runs it for a little, then shuts off again. I guess this makes sure the battery temperature is even in all areas.
     
  3. gavine

    gavine Petrol Head turned EV Enthusiast

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    I don't think it's the heat exchanger fans. It's the HVAC fan, unless they are the same fan. As I said, I can feel the air coming out through the door handles.
     
  4. andydoty

    andydoty Member

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    Well, it's reasonably cold. Perhaps it's heating the battery?
     
  5. Blu Zap

    Blu Zap Grinning member

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    You guys are on it. The MS will cool or heat the battery as needed to make sure it is at the optimal temperature for charging. This is a combination of the battery coolant pump and the car temperature itself. You may also notice a water puddle under the front passenger side bumper sometimes. This is most likely to occur if the car is being occupied when charging. Tesla stores deal with this all the time as customers are sitting in the cars, playing the stereo and running other accessories while the MS is parked and charging. Condensation from the compressor.
     
  6. gavine

    gavine Petrol Head turned EV Enthusiast

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    I wonder why it stops then, when I open the door.
     
  7. David99

    David99 Active Member

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    I know it doesn't seem to make sense. Here is another one that puzzled me. I was at a Supercharger in Quarzsite and it was pretty hot. The car cooled the battery by running the fan full blast. When I came back, sat down and turned on the AC the fan slowed down! It made no sense as there would now be more demand for cooling, not less. To test it, I turned off the cabin AC and guess what, the AC fan started running up to full speed again.
     
  8. Lloyd

    Lloyd Active Member

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    The difference is passive cooling and active cooling. When you turned on the AC, you started Active cooling, thus the lower need for external fans.
     
  9. David99

    David99 Active Member

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    That's what I was thinking, too, but then, AC or not, it is the same amount of heat that needs to be 'moved' from the battery to the outside so the radiators would need to work just as hard to dissipate the same amount of heat. Maybe I'm thinking wrong?
     
  10. jerry33

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

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    When the A/C is on, the coolant is at a lower temperature, so less need for fans.
     

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