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Battery thermal management - does it work when car is unplugged?

Discussion in 'Model S: Battery & Charging' started by johndoe74, Jun 29, 2012.

  1. johndoe74

    johndoe74 Member

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    Does anyone know whether the battery thermal management system will kick in, while the car is parked and unplugged? I am guessing not, as it would mean running the A/C system without plugged in for extended period of time. Here in AZ, the road surface temp can hit 120F+, even my garage hits 110F at night. I am a little worried about the long term effects of this on the battery life.
     
  2. brianman

    brianman Burrito Founder

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    My understanding is that cabin AC and battery thermal management are different systems.
     
  3. Jason S

    Jason S Model S Sig Perf (P85)

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    Different systems and the battery is kept cool enough. I don't know if 110 is too hot or not; it could be that it is cooled to a target temperature above that.

    If parked in your garage the general assumption is that it'll be plugged in. If parked in a hot parking lot the assumption is that you have a few Kwh left to allow the relatively low usage needed to cool the car.
     
  4. donauker

    donauker Member

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    I don't know on the Model S, but the Roadster will use the AC to cool the pack when the car is parked and unplugged if the battery temp gets to around 40C.
     
  5. jomo25

    jomo25 P4398

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  6. dsm363

    dsm363 Roadster + Sig Model S

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    The car is basically always 'on' from what I understand at least. The battery temp is closely monitored at all times and is liquid cooled in the Model S.

    from Model S Specs and Standard Features | Tesla Motors

     
  7. NigelM

    NigelM Recovering Member

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    Yes, it will.
     
  8. NuclearPowered

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    If the ambient temperature is 110f, how long can you park unplugged without the battery management system shutting down due to low power. Assume an 85 kwh pack.

    Sent from my DROID BIONIC using Tapatalk 2
     
  9. jerry33

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

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    I don't believe this is known. The only official word (from the Tesla Blog) is "For example, a Model S battery parked with 50 percent charge would approach full discharge only after about 12 months. Model S batteries also have the ability to protect themselves as they approach very low charge levels by going into a “deep sleep” mode that lowers the loss even further"

    From this I'd estimate four weeks but we won't really know until someone tries it. I expect most owners will be having too much fun driving to do this kind of test anytime soon. Maybe Tesla will release some better numbers.
     
  10. Jason S

    Jason S Model S Sig Perf (P85)

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    They've claimed a month even if you parked it at 'empty'. However I doubt that is at 110 average ambient temp. (110???????!! You parked it on a sand dune in summer in the Sahara?)

    Again it all depends on what temp is too warm for the batteries. If the temp is 160 and it isn't being driven, then the one month claim should still hold.
     
  11. brianman

    brianman Burrito Founder

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    I suspect you're trying to understand the extremes for your climate, rather than nitpick. Assuming that...

    Phoenix Weather by Month - Average Monthly Temperatures in Phoenix AZ - Hottest and Coldest Days in Phoenix
    Warmest ever by month: 1/100, 2/105, 3/113, 4/122, 5/121, 6/116, 7/112, 8/106, 9/96, 10/84, 11/86, 12/92
    For any car, I'd keep it in the shade for at least April through July. Garage would be preferred.

    Leaving it unplugged for four months (worst case starting in April) in direct sun you're just being foolish. And your paint will likely dull too.
     
  12. dsm363

    dsm363 Roadster + Sig Model S

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    If you're going on a really, really long trip anyway, taking a car service or taxi might end up being cheaper than paying airport parking fees so you could leave your car in the garage at home plugged in. For more typical vacations, it won't have a problem sitting unplugged.
     
  13. johndoe74

    johndoe74 Member

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    I think NuclearPower most likely meant how long can the 'self-cooling' battery thermal system kick in, if parked without plugged in for within a 12 hour period? e.g. Leave the house in the morning with 90% SoC, then park at work for 8 hours without plugged in at 60% SoC. Here in AZ summer, even though the ambient temp is 110F, the asphalt can reach 120 to 130F. Will the BMS attempt to keep the battery temp at 85F in this case? It would probably take a huge amount of energy to cool the battery for 8 hours straight without plugged in.
     
  14. jerry33

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

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    That is what I assumed he meant [how long can the 'self-cooling' battery thermal system last]. I'd still think quite a while (weeks) because the battery has a large thermal mass and there isn't any power being used to move the car (and cause the batteries to heat up). The car is shading the parking spot so unless you arrive at work at noon the ground will not be giving off that much extra heat. Setting the a/c to 85F doesn't even trigger the recirculation light in the Prius on an over-100F day in Texas, so I wouldn't expect the Model S to use any more energy than the Prius a/c to keep the battery cool--probably a lot less. It doesn't take a lot of energy to keep things cool. If the system had to bring the battery temperature down to 85F from 130F that would be a different story.
     
  15. surfingslovak

    surfingslovak Member

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    #15 surfingslovak, Jun 30, 2012
    Last edited: Jun 30, 2012
    Right, I would like to know more about that too. I believe that the Volt stops drawing energy from the pack when it reaches 75% SOC. I'm not sure if this is relative or absolute SOC. If it was relative, then the pack would be at about 63% true SOC. If you look at the graph I pulled from a report on generic LiMnO4 cells, then there is a good chance that the processes which degrade the battery have slowed down sufficiently at this SOC. Please keep in mind that the cells Tesla is using are a different chemistry, and this chart might not be entirely accurate.

    There is a similar discussion on the Volt forum, and although the vehicles are designed differently, hopefully some of these observations are relevant to Model S. A Volt owner in Phoenix reports that his TMS turns on periodically every 15 minutes, and he sees a 800 Watt power draw.

    If my math is correct, then this would amount to about 0.2 kWh energy usage per hour. If you consider that ambient temps come down a bit at night, even in Arizona, it might be reasonable to assume that the cooling system consumes somewhere around 2 kWh per day. Even though, the Volt has a much smaller pack, I would be surprised if Model S needed more than 4 or 5 kWh to power the battery cooling system in a 24-hour period. My guess is that it's closer to 3 kWh in locales with extreme weather, and less than that in more moderate places.
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  16. gjunky

    gjunky Waiting for the Model ☰

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    Brian, those temperatures are in the shade. It will be considerably warmer out in the sun (and there is very little shade in Phoenix..). Still good advice to park in the shade if you can of course. I park four levels below ground in Phoenix at my office and even then it gets warm during the summer (but at least it is in the shade :) )
     
  17. Discoducky

    Discoducky Active Member

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    I'd trust what TM says and then we can easily measure the draw trend cycles overtime with varying conditions; I intend to. I'd guess about ~2kWh a day nominal in extreme conditions; very close to surfingslovak's analysis.

    And I'd bet that TM would have the car phone home to HQ if parked unplugged and draining fast or approaching critical on a steep vector as they have a vested interest in keeping batteries healthy.
     
  18. E-Revo

    E-Revo New Member

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    I think this is a great question and still needs some significant expansion. The follow-up posts have been great, but fail to answer the whole picture. I really am curious about the real world effects of the extreme heat here.

    The evening in the garage is certainly an issue, but let's not forget how cooling systems work. They are heat exchangers and typically transfer heat utilizing and air conditioning compressor or via some type of radiator to the surrounding environment. Both require an air exchange to occur with the outside the car environment. Thus keeping the Model S cool in my already 100 degree garage will increase the temperature of the garage, making the whole system work even harder? Also, what about when I am parked outside at work? I have covered parking, but it is still ~110 in the afternoon right now. How much energy will it take to cool/maintain the battery pack for 8-10 hours? Thanks!!
     
  19. dsm363

    dsm363 Roadster + Sig Model S

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    I park my Roadster without plugging it in outside in the Texas summer sometimes for hours and don't notice any significant difference in range when I get back in. The Roadster has a less advanced cooling system as well. I really don't think it will be a problem. When you're home, you should be plugging in so it's a nonissue there.
     
  20. jomo25

    jomo25 P4398

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    Being that the battery is the most expensive, and perhaps the most important part of any EV, I'd say it is worth having details on how the battery is managed. If not for any other reason than the hell that Nissan is going to face due to the essentially failing batteries in the AZ/TX/LV Leafs.

    I'm confident that Tesla's experience with the Roadsters and their overall attention to detail may make this a non-issue in the S. (An example, the Roadster EVSE brick would fault if the ambient temperature was over 105 degrees. Yes, 105.) But still, I'm not the stereotypical general population who knows much less about the potential issues. I think it's something that Tesla should address at some point, and hopefully by end of year. To me, it warrants at least a page on the website on a Model S Engineering sub site (or similar).

    And again, TX heat < AZ heat :)
     

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