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Battery Temperature Management

Discussion in 'Model 3' started by Frank Schwab, May 24, 2016.

  1. Frank Schwab

    Frank Schwab Member

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    This question is asked out of ignorance - I simply don't know how Tesla manages battery temps.

    I've read in a lot of threads about how much of a range hit we'll get in bitterly cold weather (and, yes, I consider 10F/-12C to be bitterly cold). I've read a lot about how high temperature is bad for battery lifetime (living in Phoenix, this is more my concern). My question is - how hard does Tesla try to keep the battery in a reasonable temperature range?

    1. Does the car try to warm the battery in bitterly cold weather using the heater when it's parked? This would seem to be a bad idea when unplugged, but might be a REALLY GOOD IDEA when plugged in.
    2. Can I heat the battery through the phone app before I go outside? Seems like a few kilowatts expended through the resistive heater might liberate more than that from the warmed battery pack.
    3. Does the car try to warm the battery when driving by using heat from the motor? I believe that both the motor and the battery pack are liquid cooled, so it should be possible to get free battery heating by simply running the coolant in a loop through both.
    4. Does the car try to cool the battery in hot weather? When June/July rolls around and every day is above 110F/45C and the worst ones above 120F/50C, will the car try to actively cool the battery when it's parked? How about parked and plugged in? I can protect the car at home, but not so much at work.

    Thanks for any info you've got.

    /frank
     
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  2. JeffK

    JeffK Active Member

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    Nothing to do with battery "lifetime" but instead think "usable battery capacity".

    1. No, That wouldn't make any sense unless you purposely turned on the heater via the app. If it did it by itself while parked all the time you'd end up with a drained battery
    2. Yes, you can do this. It's best to do this while it's plugged into the wall as to not drain your battery.
    3. They should be on different coolant loops see Patent US20100025006 - Electric vehicle thermal management system
    4. The car will cool the battery when the battery gets hot regardless of outside temp. There's no reason to cool it when parked. The battery is kept cool during charging though as that generates a lot of heat.
     
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  3. Booga

    Booga Member

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    I think I read that the Leaf has a feature to combine points 2 and 4, and I'm guessing Tesla does too. They let you top off the charging at a certain time (1 hour before your commute for example). It benefits you if you wanted that charge and also creates some heat to decrease battery use for heating.
     
  4. Frank Schwab

    Frank Schwab Member

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    Cold temperatures relate to "usable battery capacity". No harm to the battery in cold temperatures, just a reduction in the number of electrons you can coax out of it.

    Hot temperatures, however, do harm the battery. Storage at elevated temperatures (think parked outside at 4:00 PM in Phoenix in June) seriously increases battery degradation. So, in some places it does make sense to cool an idle battery, even when parked. Hmm, an interesting question - if I committed 50 mi/day worth of range to keeping the battery cool when parked, do I have a better battery lifetime than not doing so and leatting the battery get hot?
     
  5. JeffK

    JeffK Active Member

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    The battery is literally in the shade (under the car) and has coolant throughout it. This is very different than the heat generated during operation which I'd be more concerned about. Don't think of it as a baby left in the car on a hot day.
     
  6. gregd

    gregd Member

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    I was very concerned about this - draining the battery while the car sits in the parking lot at work on a sunny day - but as far as I know in the year I've had my Roadster, it's yet to even kick in. It takes a long time to heat up that much mass, and the active cooling that takes place while charging (even if charged in the morning) sucks out enough heat that it never gets warm enough just sitting there.
     
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  7. mkjayakumar

    mkjayakumar Active Member

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    The tarmac under the battery will be several degrees hotter than the ambient air temperature. So if you are driving or parked on a hot day in an open lot on a 110F evening, then expect the tarmac to be at alteast 115F+. Since the pack is so close to the ground, the radiated heat from the tarmac will be very intense that is what the BMS has to counter.
     
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  8. zenmaster

    zenmaster Member

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    Battery temp managment is an area that definitely needs more work by Tesla. Is the energy required to heat it to ideal temp in cold weather actually more than the 1/4 or more kWh lost? Also the car will go into "limp mode" if a certain amount of hard acceleration is attempted in a period of say 5 minutes.
     
  9. int32_t

    int32_t Tesla Spotter

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    Yes, you're right. Hot can cause damage, while cold is only temporary. Without even altering the temperature of the battery, however, there is still a way to mitigate the degradation caused by extremely hot temperatures: store at a lower state of charge. Even at higher temperatures a lower state of charge (say, 40-60%) will improve overall lifetime compared to storing at the same temperature at 100% SoC. This is info from a US study done a couple years ago which I don't feel like finding just now.

    I (am confident I) heard elsewhere on this forum that the Model S won't do any type of temperature control for the battery on 120V because there really isn't enough power there to charge and heat/cool at the same time. If that's the case, I would expect it to keep the battery comfortable if the vehicle is plugged in to something more substantial, be it a Supercharger or Level 2 or something.
     
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  10. SageBrush

    SageBrush Active Member

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  11. JeffK

    JeffK Active Member

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    That's right. (different loops doesn't mean they aren't connected)

    The battery system has loop that connects to the same heat exchanger that the HVAC loop connects to. The drive motor loop is coupled with the HVAC system through flow control valves that allow you to pipe in heat from the motor to HVAC system.

    The patent explains everything in the summary section.
     
  12. scaesare

    scaesare Active Member

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    I'm not so sure this is true. Other EV's , such as the Leaf, had premature batter degradation in hot climates due to lack of thermal management. They subsequently added such to later models precisely for pack longevity reasons.
     
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  13. scaesare

    scaesare Active Member

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    A(nother) picture is worth 1024 words:

    [​IMG]
     
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  14. garsh

    garsh Re Member

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    AFAIK, Nissan added a heater to the battery pack (in 2012) for dealing with sub-zero temperatures, but they did not add any additional cooling capabilities.
     
  15. Kimo

    Kimo Member

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    I wonder what kind of solution the Model 3 will have at its price point. I can't imagine it will have all of the tech from the S, and I am curious if one area of cost savings is in the cooling/heating of the battery.
     
  16. techmaven

    techmaven Active Member

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    Tesla's NCA battery chemistry (nickel cobalt aluminum) is far more heat tolerant than the chemistry in the Nissan Leaf. Matter of fact, the difference in degradation is hard to tell at 50 degrees C versus 25 degrees C. Hence the active cooling target is 55 degrees C, or 131 degrees F. One also gets more energy out of the pack at a higher temperature, hence the ludicrous mode's max battery power setting causes it to heat up the battery. But yes, one of the reasons for much higher vampire drain of Tesla vehicles is the active battery management that will step in to protect the pack.
     
  17. JeffK

    JeffK Active Member

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    On the contrary, I bet it will have the best thermal management possible out of anything in the Tesla lineup so far. I hear about quite a few people with the Model S and coolant problems leading to battery issues including multiple drive battery replacements on the same vehicle. Warranty costs are still high.
    With a higher volume car, Tesla can afford even fewer of such issues. These battery packs need to be made to last.
     
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  18. Kimo

    Kimo Member

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    While I agree to some point, having the best thermal management possible, in my mind, has a high cost which may not be supported in a $35k vehicle. The S, I assume, currently has the best thermal management possible, so in my mind taking what the S has, making it even better, an putting into the model 3 doesn't equate from a cost perspective. I generally see it as taking what the S has, and making it "cheaper", while meeting a specific acceptable thermal management goal.

    I am very curious to learn if other aspects of the 3 will have similar "make it cheaper" aspects, such as not having full time 3G/LTE connectivity (maybe offering it as an option/upgrade/subscription), reducing or eliminating over the air software updates/enhancements and getting them during the yearly service checkups, lower warranty periods (6 year / 100k for the battery), etc. I would love to have an S, as I feel it is a technology playground for the user, having full control and information for just about everything within the vehicle. I really hope the 3 will be similar and not locked down / limited because it is mass produced.

    Thoughts?
     
  19. SageBrush

    SageBrush Active Member

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    That is AWESOME
     
  20. JeffK

    JeffK Active Member

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    These things are nearly negligible costs when compared to how much it'd cost Tesla for warranty related costs on a lower gross margin car.

    The make it cheaper things are fairly straightforward:
    Easier to manufacture
    More steel than aluminum
    Smaller battery.

    those alone will dramatically affect the price. Nickel and diming the features Tesla is known for would be a very bad move.
     
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