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Insulate the battery in cold weather?

Discussion in 'Model S: Driving Dynamics' started by billarnett, Feb 3, 2015.

  1. billarnett

    billarnett Member

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    Given that the Model S uses much more energy in cold weather I have to assume that it's continuously heating the battery to keep it up to an acceptable temperature. But it would take less (a lot less?) energy to do so if there was some insulation between the battery and the cold air blowing underneath the car. A few mm of closed cell foam covered by a thin water-proof film ought to do the trick. Maybe just glue it on in fall and scrap it off again in spring?
     
  2. scaesare

    scaesare Active Member

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    I've thought about this some.

    The leading edges especially would need attention to avoid catching the air at high speeds.

    I've mulled over some fastening ideas that might utilize the box-channel that runs longitudinally down the pack...
     
  3. Zextraterrestrial

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    I have always though that looked like it was made for a neoprene sheet but not sure what that would actually do since there is still a lot of exposed metal
     
  4. scottm

    scottm Active Member

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    It's good to see I'm not the only one who thinks of stuff like this.

    Whatever goes on, has to have a good skin - taut, smooth, non-porous.
    R-factor matters. What is the BEST R-factor material per inch of thickness?
    I'm thinking maybe you get to add an inch overall thickness before it just starts hitting to many things or gets dings from road hazards (speed bumps?)
    The car is pretty aerodynamic. Anything added will change drag, which could outweighs the benefit of retaining heat.
    More / lower front air dam?
    Whatever goes on, will get damaged. It should be cheap and easily repairable (filling in a section).
    I can't see taking it off in summer... does a battery get too HOT then?

    I was also thinking of at "at rest" solution, only.
    Something that seals the area under the car to trap the air there while parked.
    Maybe a deployable inflatable doughnut curtain around the edge of the car, using the road as the other sealing surface.

    Crazy hey?
     
  5. scottm

    scottm Active Member

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    #5 scottm, Feb 3, 2015
    Last edited: Feb 3, 2015
    This thread will probably get moved from driving and dynamics, to batteries and charging.

    Depending on whether the insulative idea is a moving one, or a fixed one.

    Hey, I like what this person had to say over in Doug's blog on cold weather driving:

    What if like a chicken, tesla roosted on a bed of SM insulation when parked in my carport (using air susp to ride in and lower onto?)​
    Updated 2015-01-15 at 04:01 PM by andyro

    I love that idea!

     
  6. scaesare

    scaesare Active Member

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    #6 scaesare, Feb 3, 2015
    Last edited: Feb 3, 2015
    The Track of a Model S is ~5.5' and the wheelbase nearly 10'. From my observation of how far the pack extends, I'd estimate it to be roughly 4.5' x 8'. That's ~36 ft^2 of non-insulated of surface area made of heat-conducting aluminum on the exposed bottom of the vehicle.

    I believe the channels are probably 3/8" thick or so:

    2013_tesla_model-s_det_lt_11071301_600.jpg

    fe_9171226_600.jpg

    I'd expect even 1/4 - 3/8" sheets of high density polystyrene or other dense insulating foam between the channels would make a significant difference. Even a 1/8" styrofoam cup allows you to hold 200 degree coffee comfortably in your hand... likely a 100 degree delta.

    A cover of tough laminate-style material could be affixed over it, with "button-style" anchors that could be slid in to the box channel to help support it. The front and side edges could be affixed with removable adhesive to keep the wind from ripping it off the bottom.

    I'd suspect a huge amount of thermal conductivity could be eliminated this way, with the overall solution protruding almost no lower on the bottom of the pack than the channels already do.
     
  7. RiverBrick

    RiverBrick Active Member

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    I like most of these insulating ideas. Even when parked, the battery can cool off quite quickly, leading to loss of regen, slower charging, and energy lost to reheat the pack.
     
  8. Evbwcaer

    Evbwcaer Member

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    I had also looked into this. The channels that run the length of the battery have edges and I thought you could slide strips of corrugated plastic, like the stuff that political yard signs are made of, into. While the stuff does not have a great R factor, it would block all the wind and moisture, is cheap and tough, and would be easy to install. It would make a huge difference in how much heat would be pulled off the battery at highway speed.

    Does the battery have any insulation at all?

    My concern would mainly be with heat generated while supercharging, but I have never supercharged and these strips could be removed easy enough.
     
  9. Jaff

    Jaff Active Member

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    I'm no battery expert, but I think this battery insulation would absolutely have to be removed...you'd cook the battery in the summer...

    That said, a removable insulation blanket might be a very good idea if it can be done in an economic manner...

     
  10. Evbwcaer

    Evbwcaer Member

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    Agreed. It would have to be removed in warm weather, probably even cold weather while Supercharging.
     
  11. AudubonB

    AudubonB Mild-mannered Moderator Lord Vetinari*

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    You guys on this thread are stealing some of the thunder (albeit one of the minor ones) from my basket of TeslaTruck ideas...... :cursing: :biggrin: :cursing: :biggrin: :cursing: :biggrin:

    Long-haul truckers, and some with leetle thangs like pickup trucks, consistently insulate their fuel tanks and lines on a seasonal basis to keep even diesel #1 from turning to snot during winter along the Alaska's Haul Road and other science-fiction-like WinterWeatherWonderways. There is no analogous reason the "fuel tank" - ie, the battery pack - on an EV also not be so protected against what hurts it the most.

    Retrofitting the Model S pack would be less elegant than a solution that was designed at time of conception. Moreover, so long as those in charge of making these decisions are more influenced by environmental factors like central and southern California weather, and the present-day distribution of TM vehicles, then we may not see any progress in this direction. Too bad, but I think I'll leave that provocative statement as the challenge that I meant it to be.
     
  12. arg

    arg Member

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    My previous thinking was that insulation while parked was the more practical and useful place to start.

    That's partly because I live in a relatively temperate climate, but even people in Canada seem to report that only the most extreme weather requires continued battery heat during a long journey (ie. after everything is warmed up, waste heat is usually sufficient to keep it there) - so reducing the need to heat after starting off in the cold (and avoiding limited regen) seems like the big win.

    There's two aspects to it: trying to keep the heat in after you've arrived home with a warm battery so that it's not as cold as ambient when you come to use the car again; and improving the efficiency when you are explicitly heating the battery (charging, pre-heating) by reducing the heat leaking out - hopefully reducing the warm-up time and directing a greater proportion of your charge energy to actual charging rather than heating.
     
  13. Saghost

    Saghost Active Member

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    Why? The Model S has a full range TMS and liquid cooling for the battery, including the ability to hold the pack below ambient at high outside air temperatures. There is probably a range of outside temperature in the middle where passive cooling is more efficient, but the car's systems can clearly handle more heating or cooling load than that - and in that limited temperature band the car would just be passing more heat to the radiator through the cooling pumps it is running anyway if you insulate the pack. By the time you get to temperatures where the insulated pack needs air conditioning, the uninsulated one will too - and you'll reduce the required air conditioning load by having the insulation.As far as I can see the only downsides to the insulation are the cost, weight, and aerodynamic impacts, along with any effect it has on accessibility/serviceability - a well designed installation should have minimal impact to all of these, and will reduce both heating and cooling losses substantially I would think.Walter
     
  14. 46&2

    46&2 Member

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    Are you sure about the assumptions?


    correct, obviously.


    Assumed, but correct I think. But take into consideration: Once the motor has reached a certain temperature, the heat generated from the driving unit is used to keep the battery warm - so the energy taken from the battery to keep itself warm is not that big anymore.
    Do you know this is that much LESS than the energy used to cool it in summer? I'm not...

    So, even though
    is correct, that does NOT necessarily mean that this, the second part of your sentence, is the (only/main) reason the range drops in cold weather (first part of the statement)! It's not a mandatory, logic conclusion, as such.

    As posted by Mr. Straubel lately, the density of the air has to be taken into consideration - cold means much more resistance! Plus, of course, water/snow on the surface you drive. So battery heating might not be such an issue, maybe, quantity wise, plus the isolation might make for a bigger air resistance.
     
  15. wycolo

    wycolo Active Member

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    Cold weather commuters could try insulating the battery from underneath while parked in a cold garage overnight. But don't use old urethane foam pieces, as I have previously suggested, as that stuff is *highly* flammable!! :scared:

    If they have air suspension they could use several moving blankets laid over a plywood base to lower the car onto. The energy savings should be sizable and easily measurable.
    --
     
  16. scaesare

    scaesare Active Member

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    My gut feeling is that this is correct.

    A quick glance at that spec sheet for the Panasonic NCR18650B says that the upper temp limit for charging is 45deg. C (113 F). I expect that is the worst case scenario for the high-temp situation... sa discharging doesn't generate as much heat as charging, and the battery can withstand temps up to 60deg C (140F). (I understand this is not the same battery, but likely close)

    Ambient temps on a hot summer day can easily reach or exceed that in many circumstances... the insulation might actually help the thermal mgm't system keep the pack cool during supercharging without having hot asphalt radiating heat up in to the belly of the pack...
     
  17. scottm

    scottm Active Member

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    Someone with a thermal imager and a lift please take pictures of a pack from underneath, coming in from driving in the cold.

    Then, let the car soak in the cold overnight or something, and drive it onto the lift again and take more images as the car is pre-warming.

    A picture would say a lot about where insulation might help the most. Maybe the whole pan doesn't need it.

    Such tools are used here to scan housing insulation from inside the house, on a cold day. You can literally see a missing section of insulation, big blue and purple area in a field of yellow orange.

    Thanks
     
  18. scaesare

    scaesare Active Member

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    Actually, I was going to add that to my last post, but forgot... you reminded my I was going to try and aim my IR thermometer at the pack in my garage and maybe take it with me next time I'm supercharging...
     
  19. deonb

    deonb Active Member

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    Just a thought...

    Tesla has obviously engineered the battery in a certain way, with coolant working a certain way, relying on among other things, the baseplate to dissipate heat etc.

    So they have sensors all over the place to measure temperature - but of course you can't have a sensor on every square inch - a lot of it will be derived based on a combination of various sensor measurements. So during design and testing, the Engineering team must have used IR Cameras and other tools to get a true profile of the overall pack, then decided where they most efficiently can put the least amount of sensors to give a approximation of what the IR Camera was truly measuring.

    However, if you now go and stick a piece of insulation over the biggest heatsink in the car, the heat dissipation will behave differently, and you'd have no idea which derived measurement will be wrong as a result, and bad stuff can happen - including voiding the warranty (This counts as altering).

    2c's.
     
  20. ThosEM

    ThosEM Space Weatherman

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    What makes y'all think the pack is uninsulated? Is there evidence of that or are you just assuming it to be the case? It seems to me that I've seen elsewhere assertions that the pack is insulated, but looking for them I don't find anything definitive from Tesla or someone who has deconstructed the battery.
     

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