Aerodynamics Won't Help Range Loss in Cold Weather

[sandpiper]

Don't bother. It depends mostly on whether you have the HVAC set on fresh or recycled. Use those heated seats...

Some other very minor effects:
1) A (physically) smaller battery pack will cool down quicker.
2) The taller batteries used in the new packs, will cool down slower.
Both due to that same surface to volume issue.

Yes, cold sucks, and the better we get at using our energy efficiently the more we will notice that suckage.

Thank you kindly.

Below -20 it's not possible to use recycled air; the windshield frosts up. The heated seats help a bit. But (trust me) they do not lessen the pain associated with the complaining from your family, as they wonder why they're sitting in a 6 figure car but have to have freezing cold feet for 3 hours.

My point is and remains... in Canada get the biggest battery available and if need be forego some of the creature comforts.

 

[dhanson865]

I think you've got that bit backwards.

Indeed I did, I was thinking of a counterintutive effect of tire rubber choice and misspoke.

Assuming you are tracking one tire with no changes other than temp, lower temps equal less rolling resistance.

 

[dhanson865]

Correct. That's backwards. That's why winter tires are so important. I learned that lesson, one New Years Eve, well after midnight. I had all season tires on my van, and when the light turned red, I hit the brakes, and slid right through the intersection. Good thing there was no traffic due to it being so late. Winter tires remain soft throughout the winter, offering more traction and therefore better braking.

more traction = more rolling resistance.

That is a tire compound choice you need to make for traction but there are temps where each tire compound has it's optimal properties. Just because the "winter tire" had a softer compound doesn't mean softer compounds equal lower rolling resistance.

 

[diamond.g]

Below -20 it's not possible to use recycled air; the windshield frosts up. The heated seats help a bit. But (trust me) they do not lessen the pain associated with the complaining from your family, as they wonder why they're sitting in a 6 figure car but have to have freezing cold feet for 3 hours.

My point is and remains... in Canada get the biggest battery available and if need be forego some of the creature comforts.

Does preheating not help?

In -5F I have seen my TDI heat gauge go back down if I am running the heat and going more than 45mph.

 

[Topher]

Below -20 it's not possible to use recycled air; the windshield frosts up. The heated seats help a bit. But (trust me) they do not lessen the pain associated with the complaining from your family, as they wonder why they're sitting in a 6 figure car but have to have freezing cold feet for 3 hours.

Not that it would address the energy issue, might even exacerbate it, but does your Tesla not allow dehumidifying when in heating mode? My Prius does.

My point is and remains... in Canada get the biggest battery available and if need be forego some of the creature comforts.

No argument there.

Does preheating not help?

A bit, but sandpiper is right, humans pump out a lot of moisture breathing, and cars just aren't well insulated; that means cool interior surfaces, cooler than the dewpoint of that moisture laden air, which means condensation (or ventilation).

Thank you kindly.

 

[sandpiper]

Does preheating not help?

In -5F I have seen my TDI heat gauge go back down if I am running the heat and going more than 45mph.

It helps a little in that you don't need to expend the energy required to bring the pack up to temperature initially. But after a half hour on the road, the pack has gone to steady state temperature irrespective.

My -25C, 250km highway range on a P85D assumes a pre-warmed pack in a heated garage. If it's cold-soaked from being outside, your range will worse. That's the simple reality.

 

[sandpiper]

Not that it would address the energy issue, might even exacerbate it, but does your Tesla not allow dehumidifying when in heating mode? My Prius does.

Yes of course it does, but in most cars that I'm aware of it only takes place when the A/C is running. To my knowledge there is no dehumidifier that runs when the HVAC is off or heating. But of course when you're heating you don't need it; heating naturally reduces the relative humidity.

The Tesla is very well sealed, and it picks up humidity very quickly with the HVAC off.

 

[diamond.g]

It helps a little in that you don't need to expend the energy required to bring the pack up to temperature initially. But after a half hour on the road, the pack has gone to steady state temperature irrespective.

My -25C, 250km highway range on a P85D assumes a pre-warmed pack in a heated garage. If it's cold-soaked from being outside, your range will worse. That's the simple reality.

Ah, I seem to recall the Model S having 6(battery)+6(cabin) kw of heating, but it appears that (according to Tesla) the PTC may just not work well under -20C.

 

[diamond.g]

From the Volt forums, it appears that going with a heat pump won't help at all at such low temps.

 

[Topher]

Yes of course it does, but in most cars that I'm aware of it only takes place when the A/C is running. To my knowledge there is no dehumidifier that runs when the HVAC is off or heating. But of course when you're heating you don't need it; heating naturally reduces the relative humidity.

No, that's what I meant. A Prius will run the AC along with the heater to reduce humidity.

Heating does reduce the relative humidity by raising the temperature of the air, but if there are still cold surfaces, they will still condense moisture, since you haven't raised the dewpoint. Which is why defrosters are aimed directly at the windshield.

Thank you kindly.