Model Y - Just OK cold weather car

[rjpjnk]

The humidity removal provided by the AC evaporator is an important part of the defogging process. This is true whether the air is (also) heated or not.

 

[YSleipnir]

I guess you never lived in the south... Steamy summer showers fogs up the windows pretty bad

Indiana too. Windows can fog up in spring and summer due to humidity. Also they can do that in the winter and fall. We also can be subject to sunny warm weather and snow/ice on the same day. That's a lot of tire swapping.

 

[sleepydoc]

I guess you never lived in the south... Steamy summer showers fogs up the windows pretty bad

Yeah, the climate in Georgia is a bit different than it is in Ontario!
All modern cars automatically turn on the A/C with the defroster but I was never clear if they do that even when it's cold and what the benefit is. In the winter the air is so dry you really don't need to dehumidify it; simply heating it is enough.

 

[Volleyballmom]

... drives me nuts when I see posters showing videos claiming their Y is great in the snow with the stock all seasons because they can get it to move properly in a straight line and/or up a hill in 8" of snow or pull another vehicle. Of course you can, Heck, you could do most of it in summer tires as well, albeit even more carefully.

The main point is the ability to stop and/or manouevre unexpectedly, that's where winter tires show how much better they are than all-seasons.

@gt2690b that's not aimed at you since it sounds like you plan on getting winters.

Yeah, the climate in Georgia is a bit different than it is in Ontario!
All modern cars automatically turn on the A/C with the defroster but I was never clear if they do that even when it's cold and what the benefit is. In the winter the air is so dry you really don't need to dehumidify it; simply heating it is enough.

Ever have 4 adults in the car after a few hours of hard skiing? Everyone's breathing a little harder than normal. Boots & clothes + gloves are damp + covered in snow, which produces a lot of water and humidity in a warm car (which needs to be warm cuz of the frozen toes). Humidity is much more of a problem in the winter than in the summer in Quebec. Fortunately, my MY outperforms any other vehicle I've ever owned in this respect.

 

[sleepydoc]

Ever have 4 adults in the car after a few hours of hard skiing? Everyone's breathing a little harder than normal. Boots & clothes + gloves are damp + covered in snow, which produces a lot of water and humidity in a warm car (which needs to be warm cuz of the frozen toes). Humidity is much more of a problem in the winter than in the summer in Quebec. Fortunately, my MY outperforms any other vehicle I've ever owned in this respect.

Yes - that's a pretty extreme circumstance but the A/C would definitely be helpful there. My thought is if it's taking in dry outside air, heating it and blowing it on the windshield it's typically more than adequate and you don't waste energy on the A/C. It seems like it would make sense to have the A/C off by default below a certain temp and let people turn it on for situations like you describe.

 

[boulder.dude]

Yes - that's a pretty extreme circumstance but the A/C would definitely be helpful there. My thought is if it's taking in dry outside air, heating it and blowing it on the windshield it's typically more than adequate and you don't waste energy on the A/C. It seems like it would make sense to have the A/C off by default below a certain temp and let people turn it on for situations like you describe.

I suspect in an EV (where waste heat isn’t “free”) it’s more efficient to dehumidify warm inside air than it is to heat cold dry outside air?

 

[boulder.dude]

The front windshield defogger (icon turns blue) turns on the AC to remove condensation from the inside of the windshield. In certain weather conditions it is essential to being able to see out of the windshield, side glass. This is more efficient and quicker than heating up the windshield (heating up the windshield can also defog the glass.). The heat pump in the Tesla Model Y can remove moisture from inside the passenger cabin and the heat the air in the passenger cabin at the same time.

Drove my MY in a cold (20F) blizzard and kept the climate control in auto. The car kept the windshield cold enough so that snow didn’t melt and stick – snow stayed “dry” and the wipers just whisked it away. No Ice buildup. This was a surprise for me after driving ICE cars for 20 years and keeping the windshield as hot as possible in snowstorms. So maybe there is a method to the “madness” of the Tesla defrost system?

 

[sleepydoc]

I suspect in an EV (where waste heat isn’t “free”) it’s more efficient to dehumidify warm inside air than it is to heat cold dry outside air?

Yes, that may be true - the equations change when you’re looking at EVs.

 

[patnshan]

I’ve read (and noticed in our recent snows here) that the Y is essentially RWD in slow city driving, causing the rear end to lose traction in turns. Have you tried Off Road Assist in snow? It forces a 50-50 power split between front and rear axles, although you lose traction control. I’d be interested to hear your thoughts.

This works for me on acceleration. But still does not fix the overzealous regen on slowing that you cannot turn down. The latter is a huge problem.

 

[gt2690b]

I suspect in an EV (where waste heat isn’t “free”) it’s more efficient to dehumidify warm inside air than it is to heat cold dry outside air?

does manual heat mode (with AC off) use more energy than auto heat mode with AC on since maybe turning AC off disables the heat pump?

 

[jcanoe]

does manual heat mode (with AC off) use more energy than auto heat mode with AC on since maybe turning AC off disables the heat pump?

There is no manual heat mode. There is no resistance heating unit (other than the rear window defroster grid) in the Tesla Model Y; the heat pump performs both heating and cooling for the passenger cabin. The high voltage battery is warmed, as required, using heat generated by the motor stators (front and rear, up to 7kW when both front and rear motor stators are generating heat for the battery.) Once the battery has been sufficiently warmed the coolant from the battery can be used by the heat pump to help warm the passenger cabin.

 

[gt2690b]

There is no manual heat mode. There is no resistance heating unit (other than the rear window defroster grid) in the Tesla Model Y; the heat pump performs both heating and cooling for the passenger cabin. The high voltage battery is warmed, as required, using heat generated by the motor stators (front and rear, up to 7kW when both front and rear motor stators are generating heat for the battery.) Once the battery has been sufficiently warmed the coolant from the battery can be used by the heat pump to help warm the passenger cabin.

i mean.. there is a manual heat mode but i get what you're saying.. no resistive heating save for the motor stators

 

[jcanoe]

i mean.. there is a manual heat mode but i get what you're saying.. no resistive heating save for the motor stators

Correct. Unlike the original Tesla Model S, X and Model 3 the Tesla Model Y has never had resistive heating for the passenger cabin. The 2021+ Model S, X and latest Model 3 utilize a heat pump to heat and cool the passenger cabin.

 

[WattsappMTL]

Yeah, the climate in Georgia is a bit different than it is in Ontario!
All modern cars automatically turn on the A/C with the defroster but I was never clear if they do that even when it's cold and what the benefit is. In the winter the air is so dry you really don't need to dehumidify it; simply heating it is enough.

On my more recent model VWs, AC is activated whenever you direct all air to the windshield - regardless of outside temperature. You could then manually deselect it if you wanted the hottest possible output with no dehumidification. I think this is a pretty common approach for other ICE vehicles too. Tesla sometimes adds AC when it detects humid conditions in the cabin (sensor behind the rear view mirror) and the driver has the option to turn it off as needed. It occurred to me that because of the heat pump architecture, the system must be using the same compressor to cool then reheat the air, so it will use more energy in that configuration.

 

[jcanoe]

Tesla octovalve & heat pump workings overview:

 

[P3dStealth]

My model 3 doesn't have the heat pump and the resistance heater works great in winter.

My door handles are just as annoying as yours though. I just spent 10mins trying to break them all free in the cold. Even sprayed with wd40 they still get stuck. I get that they look cool and are streamline but the design of the door handles should be changed.

 

[gt2690b]

My model 3 doesn't have the heat pump and the resistance heater works great in winter.

My door handles are just as annoying as yours though. I just spent 10mins trying to break them all free in the cold. Even sprayed with wd40 they still get stuck. I get that they look cool and are streamline but the design of the door handles should be changed.

muahaha.. coming from the S the door handles are a dream!

 

[sleepydoc]

muahaha.. coming from the S the door handles are a dream!

I still don't get why they felt it necessary to make them different from every other car on the market. If nothing else the fact that you can't open them with your hands full makes them worse than everything else.

 

[rjpjnk]

It occurred to me that because of the heat pump architecture, the system must be using the same compressor to cool then reheat the air, so it will use more energy in that configuration.

Not exactly. The "reheating" in this case is done by activating a condenser coil inside the air handler rather than outside the car, so the heat that is removed from the cold evaporator coil is just moved to the warm condenser coil in the same box. This way the overall temperature is not changed much but moisture is removed by condensation so we get dry air for the windshield. The video posted above is a great way to learn more about this system. It can move heat all over the place. Inside/outside the car, to/from battery. It even reclaims left over cabin heat after a drive to use to keep the battery warm. Truly amazing system. Just wish it could hold a constant cabin temp better.

 

[WattsappMTL]

Not exactly. The "reheating" in this case is done by activating a condenser coil inside the air handler rather than outside the car, so the heat that is removed from the cold evaporator coil is just moved to the warm condenser coil in the same box. This way the overall temperature is not changed much but moisture is removed by condensation so we get dry air for the windshield. The video posted above is a great way to learn more about this system. It can move heat all over the place. Inside/outside the car, to/from battery. It even reclaims left over cabin heat after a drive to use to keep the battery warm. Truly amazing system. Just wish it could hold a constant cabin temp better.

The Tesla heat pump design is truly a marvel in the way that it optimizes heat flow. However since heat transfer is never 100% efficient, cooling and then reheating the air must use more energy than just heating it.