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3 tips to significantly increase range in winter and message for Tesla

Discussion in 'Model X' started by ML_X60D_Canada, Jan 26, 2018.

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  1. Snowstorm

    Snowstorm Member

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    Great post and informative. The only thing I would question is the energy required to warm the battery. I have a 6kw charger at home and can say that after 30 minutes, I can get the cabin to 18c and battery to at least 8c with some regen from both cold soaked at 0c. Where do you get the heat capacity of the battery from?

    Also, it isn’t necessary to heat the battery to 15c, we get around 30kw of regen at 8c and further hearing can be done with just internal resistance on driving.

    I would preheat cabin and battery, but only about 30 min for 3-4kwh worth.
     
    • Informative x 1
  2. Allanf

    Allanf Supporting Member

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    Regarding the App, a little work on it would go a long ways. We are told Range Mode must be turned off to preheat the battery when you are preheating the cabin. There should be at least a separate option to preheat the battery that, if selected, automatically turns off Range Mode. When you start your trip a pop-up message could inform you that Range Mode is off. As suggested in this thread a further refinement would ask for estimated departure time and have the battery temp optimal and cabin at desired temp at departure time. There is terrific information in this thread but engineering at Tesla has a lot more information than we would have on things like optimum battery temp at departure and the other variables affecting range.

    It looks like there are two concerns expresses in this thread - one being saving on energy usage as a cost and environmental concern and the other is increasing range. Mine is getting maximum range to avoid stopping at superchargers when i have colleagues from work in the car who want to get home. lol.
     
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  3. CHGolferJim

    CHGolferJim Member

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    Another: Turn car heater on 80*F continuously when supercharging, then turn it off and use seat warmers as long as you can stand it.
     
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  4. Joel 3

    Joel 3 New Member

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    If you have the ability to put your car in a warmed garage, do it for the battery. Will help on daily range a ton.
     
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  5. sule

    sule Member

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    I'm a long time Model S owner but...

    Drag (force) is. But power to fight it is not - it is proportional to the cube of the velocity. However, because at that power you're traveling faster, when you divide that by velocity to figure out how much energy you need per distance you get back to the square.

    After essentially five winters (March 2014 delivery but in COLD Canada) and 115,000 km and a lot of science... yes, the OP suggestions are correct but not all need to be taken entirely, such as hours of preheating. I am not saying OP is wrong. Not at all, but you reach the point of diminishing returns and really need to do this only in extreme cases. Specifically on the point of (pre)heating, it is not just about lowering the internal battery resistance but also about storing heat inside the body of the car so that less heating of the cabin is needed during the drive. If you just prewarm the air of the cabin but panels remain cold, for example, some of that air heat will dissipate more quickly than if the panels were warm too.

    So, if you want to maximize the range:

    • As the OP says, do preheat the cabin and the car so that less heating is needed during the drive. Energy efficiency aside, you may want to warm the cabin to a higher temperature than you normally would like, such as the maximum comfortable one, as that will heat the rest of the car quicker too. This will cool quickly during the drive. Do note that the remote heating may stop when it reaches the desired temperature.
    • Preheat the battery. This used to be done best by charging at maximum rate possible just before the drive and/or doing what Bjorn did. If you charge just before you leave make sure it isn't for a few seconds - it needs to last enough to warm the battery - so leave enough room in the battery to do so. You may do what Bjorn did then come back to recharge as well. Now, I haven't followed the forums in a LONG while, but recently the Tesla mobile app was updated to include something re battery heating and there was a note on heating the battery specifically while on shore power.

    • Note on the two above - cabin heating at max power can take 30A by itself (with no charging going on). 80A HPWC really helps here.

    • Drive slower. Aside from elevation (gravitational potential energy) differences, energy needed for the trip is there ONLY to fight various forms of resistance and drag. Energy needed just to fight air drag is proportional to the square of the velocity. Half the speed means quarter the energy needed (or twice the speed = four times the energy). Rolling resistance is also non-linear and worse at higher speeds. Additionally, even though the difference will be small at significant speed, slower driving will preserve more of a surface layer/effect so your car will be less cooled by the outer air than at higher speeds.

    • Do not drive too slowly. At some point the benefits of less drag will be overcome by the need to keep you and the battery warm longer. I cannot give you the exact best speed as it depends on many factors.

    • Reduce the cabin temperature - but not immediately, as you don't want the car to bring cold air to intentionally cool the cabin. This will reduce the temperature difference between the inside and outside air and, thus, reduce the heat loss.

    • Keep your climate system on full auto. Do not set custom fan speeds or otherwise. It seems to be optimized for this case. Whenever I tried to mess with it I got worse efficiency. I do NOT have a good/better explanation.

    • If you can use seat heaters instead of the cabin heat, use that. This does not work well for me, comfort wise so I don't do this ... and I haven't had success using both (with lower cabin heat - I really need my cabin heat). If you don't need cabin heat at all (snow pants?), turn it off :)

    • Drive gently. Accelerating fast will cause more slipping which wastes energy. Decelerate slower as well - avoid using breaks (complete waste of energy) and know that regen is not 100% efficient, you lose some energy. Try to remain at one speed for as long as possible. Letting the velocity reduce as you climb uphill or go up a bit as you go down may help as well - less slipping both ways.

    • Drive with traffic, especially on roads not cleared from snow/ice. Do not try to cut your own tracks in snow - use those made before you came. Additionally, air drag will be reduced for a closely spaced group of vehicles traveling at the same speed. While the closer you are the more energy efficient you will be I do NOT advise this as you risk accidents and damage from debris.

    • Use winter tires. Less slipping even though the rolling resistance may be worse. They are also incomparably safer and they do not cost extra (you're saving the other set while using winters, you're saving energy and you're reducing risks of trouble)

    • If you have a glass roof (I have the original pano roof) you may consider insulating/padding it from the inside. Bjorn did this. I did not find it necessary.

    • Attachments, such as roof racks (and whatever goes on them) or those rear racks on X increase air drag. If you don't need them, take them off.

    • Model X / wing doors special: don't use your wing doors. They let the hot cabin air out very quickly and they are slow so they do it well. Get into the car quickly to preserve as much heat as possible.

    • Fun one - have live passengers instead of the luggage :). Passengers replace air that needs to be heated with their bodies that act as heaters.
     
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  6. sule

    sule Member

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    Oh ... and range mode is useless from my experience. Accomplishes nothing but a colder cabin, which I can better achieve otherwise.
     
    • Informative x 1
  7. Cfinck

    Cfinck Member

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    Excellent post! I have a 70 and do 350mi trips every weekend. With the cold weather and increase in elevation to the mountains range becomes a huge factor!
     
  8. Graffi

    Graffi Member

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    Fortunately living in San Diego this is not needed, but I was thinking that in very cold areas someone could just build a 2 X 2 frame and cover with a very thick plastic sheeting to build a tent that could be lowered to cover your Tesla in your garage. This way you only need to heat the volume inside the tent, not your whole garage. Almost like a double insulation. This may even work for those without a garage if you have room to build it. Just a thought ....

     
  9. DataMN

    DataMN Member

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    #29 DataMN, Jan 28, 2018
    Last edited: Jan 28, 2018
    He's using 6 K W charger which takes much longer. Much less time with higher powered charging. Can't give exact numbers. Just know it does.
    Definitely need option in phone app to turn Range Mode on and off. Automatically even. Also need timer option to turn cabin heater on (and off) at preset time.
    Elon / Tesla?
     
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  10. thefortunes

    thefortunes Member

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    Actually the 6kW is referring to the max usage by the battery heater, not what charger he is using.

    I agree it would be nice to turn range mode on/off in the app, although I personally do not see a need to turn it off unless I am in the car and want to improve HVAC performance. I'm not even sure when I last had it off, to be honest, and we've had temps down to -20F recently.

    There already are options for cabin preheat timing - the built-in "smart" pre-conditioning (lol), a choice of 3rd party apps (I use TeslaFI) or your Echo or Home programming.
     
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  11. DataMN

    DataMN Member

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    Hmmm, guess his "If you have a 6 KW charger, you will need 4 hours to to generate 24 kWh..." has some other meaning. "Smart" preconditioning doesn't do any good when your are retired, have no routine and take long cold trips 'every-now-and-then'. And much prefer smart functionality over yet another app.
    Thanks for the input.
     
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  12. hacer

    hacer Member

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    Considering the effects of air-drag (the most significant loss absent elevation change at highway speeds): The second point quoted above neglects the inefficiency of converting energy stored in the battery into power to drive the wheels. As you acknowledge in the first point, power is proportional to velocity cubed. Energy lost in electrical resistance is proportional to power squared at constant voltage which is true for the battery and approximately true for the DC/AC converter system. So power lost in the battery/converter system is approximately proportional to velocity to the sixth power. Dividing by the time to get to the destination brings it down to the 5th power for energy consumption. In the motor and connections to it, the electrical power loss is proportional to velocity to the 4th power, so energy loss in that part is proportional to velocity cubed. These resistive system losses are non-trivial and even more sensitive to speed, so slowing down is a really good idea to save energy.

    I was surprised that the OP didn't mention drafting behind another vehicle because this can dramatically reduce energy consumption at higher speeds, even with 4 or more car-lengths behind a large vehicle.
     
  13. thefortunes

    thefortunes Member

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    Lol. If you "take long cold trips every-now-and-then" but don't have a routine that smart conditioning or an app can follow, what do you want? Do you want the car to just guess when you will do this?

    The native Tesla app (or Echo, or Home) already allows you to preheat/precool upon tap/command. 3rd party apps (for those people reading this who want to know options) can even do this on a schedule.
     
  14. sule

    sule Member

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    All true. But these are internal losses, not about the main power to move the car. If we get to this level of detail we'll never stop. These losses are not only nonlinear but also have a non-zero most efficient speed and other factors - if you go slower they can increase, in fact. So, if you want truly ideal/maximum range you have to account for many factors that should be something we don't think about.
     
  15. claudelaval

    claudelaval Member

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    Right on. Electricity is not that cheap in some parts of the USA and ''spilled'' 4-5 hours just to warm-up the batteries is a waste and make buying an EV not more affordable than an ICE
     
  16. claudelaval

    claudelaval Member

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  17. claudelaval

    claudelaval Member

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    I don't see anything on the Tesla App concerning heating the batteries only...
     
  18. sule

    sule Member

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    Actually, that was wine talking. It isn't all true. You say "Energy lost in electrical resistance is proportional to power squared at constant voltage". There are multiple ways and places you can approach this. In a DC world the voltage would NOT remain constant. It would change and would be proportional to the current (Uloss=Rloss*I) needed to yield actual useful power (Puse=Uuse*I) where Uuse, if simplified to a resistance would be Uuse=Ruse*I. Total power would be Ptot=(Uloss+Uuse)*I=(Rloss+Ruse)*I*I=Rtot*I².

    Thus, Ploss (which is Uloss*I = Rloss*I²) is lost, which is (Rloss/Rtot)*Ptot. In other words, Ploss is a linear fraction of the total power - and also a linear fraction of the useful power.

    Now, in an AC world things get a lot more complicated to describe here. Also, (electrical) resistive losses aren't the only losses. So no point in debating that.

    Finally, energy lost in electrical resistance is not proportional to power ever or any exponent of that because the unit is very different. You need to multiply the power with time to get the energy.
     
  19. SageBrush

    SageBrush 2018: Drain the Sewer

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    #39 SageBrush, Jan 28, 2018
    Last edited: Jan 28, 2018
    This says that the heat capacity of a Li-x battery is 0.83 J / g*Kelvin

    For a 500 Kg battery it works out to 3.45 kWh to increase temperature 30 C
    --

    Power increases with the cube of velocity, but you are interested in the energy/mile change. The Aero resistance (force) increases quadratically (to the second degree) with speed. At the same speed, the change in energy/mile is simply the fractional change in air density. So a 10% increase in air density will lead (all else being equal) to a 10% increase in energy/mile
     
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  20. sule

    sule Member

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    #40 sule, Jan 29, 2018
    Last edited: Jan 29, 2018
    Well, look at the screenshot below. Now there is that battery icon in there that wasn't there for years - it is relatively new (I've seen if at least a few weeks now, maybe longer).

    *EDIT*: Note - the icon appears a little while after the heating is turned on, not immediately. Almost enough to give up waiting and miss it - i.e. red arrows showing hot air appear first without the battery icon. [end edit]

    There was an announcement I heard or read somewhere (forgot)... but I was able to uncover the following:

    Tesla is working on a battery pre-heating feature to maximize efficiency in cold climates

     

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