Parking outside in very cold weather and not plugged in

[Andyw2100]

This is a complicated subject with many cases, but one thing is for sure: If the car is sitting in the cold, off, and not connected to any power, the battery will get much colder than -8˚C.

Again, thanks for the detailed answer.

I was pretty certain the line I quoted above was the case, so I didn't understand (and I guess I still don't really) just what the "target temperature" meant if the conditions under which the car attempts to actually achieve the target vary so greatly. (Meaning sometimes it does and sometimes it doesn't.)

Of course this does explain why we're all still trying to figure out optimal charging strategies for elimination of the regenerative braking limit, etc.

 

[jpet]

Note that the Active heating threshold is currently 8°C, not -8°C.
According to the info I have collected over the past several years, in 2013 is was 10°C, in 2014 it was 7°C and currently (as of 2015) it is 8°C.

Now the big question is: why 8° and not more or less? I believe keeping the battery as cold as possible is generally a good thing because there are less parasitic chemical reactions in the cells at lower temperatures. That's why Elon once said that he expects the Tesla battery to last forever in very cold climates, no matter to what SoC level the battery is charged on a daily basis.

There is however the drawback of a cold battery having somewhat lower capacity so less power available until it heats up to the more or less "ideal" 20°C. And this also impacts max charging power, hence the regen that needs to be limited for a cold battery. I guess Tesla has been trying to find the sweetspot avoiding both energy loss by using the heater too soon and available power & regen by not allowing the battery to become too cold when driving.

In general, cold weather = good for your battery.

 

[Cottonwood]

Note that the Active heating threshold is currently 8°C, not -8°C.

Thanks, I corrected my post.

In general active heating does not kick in while the car is off and there is no shore power, to avoid severely discharging the battery.

Think about parking your Tesla for a week at the airport in the winter. I have done this with ample margin. I lost many rated miles, but had more than I needed to get home. Active heating while parked for the week could have easily bricked the battery in a few days.

 

[green1]

also keep in mind that the battery seems to have significant thermal mass, so it does take quite a while to get down to ambient temperature, even when it's quite cold out (not saying it stays at full operating temp, but it does seem to keep some heat for a very long time)

 

[kort677]

Thanks, I corrected my post.

In general active heating does not kick in while the car is off and there is no shore power, to avoid severely discharging the battery.

Think about parking your Tesla for a week at the airport in the winter. I have done this with ample margin. I lost many rated miles, but had more than I needed to get home. Active heating while parked for the week could have easily bricked the battery in a few days.

so what is the best way to leave the car parked outside in cold temps? I am guessing it would be with the range mode off

 

[Cottonwood]

also keep in mind that the battery seems to have significant thermal mass, so it does take quite a while to get down to ambient temperature, even when it's quite cold out (not saying it stays at full operating temp, but it does seem to keep some heat for a very long time)

That is very true, but the thermal time constant of the battery seems to be measured in hours, not days. Once the battery gets cold, that big thermal mass takes a lot of energy to warm back up.

- - - Updated - - -

so what is the best way to leave the car parked outside in cold temps? I am guessing it would be with the range mode off

Range mode only matters when you start driving or charging again. In either case, with range mode off, the car will warm the battery more quickly and use more power doing so.

At very low temps (<-30˚C), the car may use active heating when it is off, but normally no active heating is done while the car is off.

With range mode off, and when the HVAC is turned on, to warm the interior, it seems that there may be some battery heating happening.

 

[svp6]

So I finally tested the updated software and the battery drain in very cold weather. I left the car at the airport on 2/6 in the morning and picked it up on 2/13 in the morning. Garage is open to the air. Daily temps as follows:

I charged in the airport a little before the departure (I knew temps may get very low) - left the car with 160 rated miles. This morning, after 7 nights I had 124 rated miles left - that gives ~5 rated miles / night. This is with every saving on (power saving on, always connect off). Not too bad.

This morning we had -4F when I arrived. I figured out I should pre-heat the battery before leaving, also add few miles more for the return trip. For the first ~45-50 minutes I saw the car drawing 30Amp at 205-210V but no charge at all - I did not think it would take so long to heat the battery. For the next 60 minutes it added ~12 miles rated range - slower than the same charger one week earlier (~16 miles/hour).

I averaged on the trip to Minneapolis 366 Wh/mi (total 81 miles, temp ~30F, slightly humid pavement. The return trip I averaged 411 Wh/mi (same distance, -2 to -5F, sunny and dry). No wind both days. This is improved compared to similar conditions last year - by ~3-5%. Both trips at 65 mph, range mode on, cabin heating at 67F.

Conclusions: Not too much loss in battery range even in extreme conditions. still need that Minneapolis / St. Paul supercharger for a more comfortable experience......

 

[InternetDude]

svp3, that is not "very cold" or extreme

 

[svp6]

svp3, that is not "very cold" or extreme

- 5 F = -20.6 C seems rather chilly, don't you think?

 

[Cottonwood]

- 5 F = -20.6 C seems rather chilly, don't you think?

Certainly rather chilly, but not extreme.

It's all relative, but my personal threshold for extreme cold is -30˚C., -22˚F. Of course for some hearty soles, it's -40˚.

 

[InternetDude]

- 5 F = -20.6 C seems rather chilly, don't you think?

-20C is just cold, very/extreme isn't until at least-30C here LOL it got down to-37C or so at the coldest last winter. That's without windchill.

 

[jerry33]

-20C is just cold, very/extreme isn't until at least-30C here LOL it got down to-37C or so at the coldest last winter. That's without windchill.

Windchill has virtually no effect on inanimate objects. It's mainly there to allow people to brag (or complain) how cold it is compared to other places.

 

[SMSMD]

FYI:

Cold Weather Driving - Blogs - Tesla Motors Club - Enthusiasts & Owners Forum by Doug_G

 

[David29]

Is this a common occurrence with the Model S when temps get that cold? We've had this on occasion with our Ford plug-ins on the coldest days, but usually they don't lose their connection until the air temp is at least -10 F or colder. And, even at those temps it is unusual. Opening their app every hour or two will keep them connected, even on the coldest days. I would hate to not have preconditioning.

Tonight I came back from a 25 mile drive at highway speeds, no restriction on regen once we'd been on the road awhile. Outdoor temp was 10F at end of trip. Parked car for a few minutes. Came back to car, both screens were off, dark. Got a message saying that "System is powering up." Never had seen such a message before. Indicated range is 43 miles, or about 18% or 12.5 KWH out of my 70 KWH battery. After a couple of minutes, the instrument cluster came up and I could drive the car, but the Main screen did not power up. I called Tesla service, who said that was a result of the battery management system preserving power to protect the battery. He recommended that I plug it in overnight, but I am not in a place where I can do that.
So I am assuming from what I have read, that I will be OK if I leaver the car outside overnight (temps predicted to drop to zero F or a few degrees less), and charge it tomorrow AM.
I could take it to as SC to get some charge tonight, but that is quite inconvenient at this hour...seems as if I will have enough charge to allow the battery to be OK> Hoping so, anyway! We'll see, tomorrow....

 

[Quantum`]

I don't know man, it is dicey. No charger near your girlfriend's?

 

[svp6]

-20C is just cold, very/extreme isn't until at least-30C here LOL it got down to-37C or so at the coldest last winter. That's without windchill.

Got it - happy we don't have those to often here. The take home messages from my 1 week open parking in Minneapolis airport were 1) not a terrible range loss in consistently low temperatures and 2) it took 45 minutes to warm up the battery on a level 2 charger - much longer than expected.

 

[David29]

Tonight I came back from a 25 mile drive at highway speeds, no restriction on regen once we'd been on the road awhile. Outdoor temp was 10F at end of trip. Parked car for a few minutes. Came back to car, both screens were off, dark. Got a message saying that "System is powering up." Never had seen such a message before. Indicated range is 43 miles, or about 18% or 12.5 KWH out of my 70 KWH battery. After a couple of minutes, the instrument cluster came up and I could drive the car, but the Main screen did not power up. I called Tesla service, who said that was a result of the battery management system preserving power to protect the battery. He recommended that I plug it in overnight, but I am not in a place where I can do that.
So I am assuming from what I have read, that I will be OK if I leaver the car outside overnight (temps predicted to drop to zero F or a few degrees less), and charge it tomorrow AM.
I could take it to as SC to get some charge tonight, but that is quite inconvenient at this hour...seems as if I will have enough charge to allow the battery to be OK> Hoping so, anyway! We'll see, tomorrow....

Follow-up: As it happened I was able to put the car back into the garage where the temp is a little higher. Moved the car about 11 PM, air temp was in the single digits (F). I had lost 4 miles of indicated range in about 4 hours, now had a snowflake on the dash (indicating range reduced to preserve some battery capacity for heating). Because the garage runs 10-15 degrees warmer than ambient air, the battery evidently stayed warm enough to keep the computer on so I was able to connect to the car with the app in the morning. But cabin heating was unavailable (through the app) due to limited capacity. I was able to start, drive, and charge the car this morning with no problem. So my hunch was right, it was OK to wait until this AM to charge, and battery protected itself. It is true that the conditions would have been more severe if I had had to leave it outdoors, and I do not know how much difference that would have made.
As a side note, charging (at a supercharger) was much, much slower than usual. The system kept the charge current quite a bit lower than usual for quite a while, presumably because the battery was so cold. I charged for about an hour and only got about 100 miles of range.

 

[green1]

Windchill has virtually no effect on inanimate objects. It's mainly there to allow people to brag (or complain) how cold it is compared to other places.

Wind Chill isn't just about humans vs inanimate objects. It is about speed of change of temperature. If an object that is 20c is exposed to air that is -30c, it will, over time, become that same -30c unless energy is used to maintain the initial temperature. This time is decreased (or the counteracting energy is increased) as more air flows over that object, we know this effect as wind chill.

On a car you would generally say it doesn't apply, and you'd be right, however there are situations where it is still relevant. For example, if you are heating the car above the exterior temperature, it will take more energy to maintain the same temperature as the wind increases, even as the exterior temperature remains constant (In the Tesla we heat not only the passenger compartment, but also the battery, the same issues apply to both). The second time it matters on a car is if the car is at a certain temperature and we park and walk away. Over time the car will cool to the surrounding temperature, but the more wind, the less time it will take. With the Tesla specifically, the battery has a fair amount of thermal mass, this means that you can park it for a short while outdoors without it cooling down all that much, even in very cold temperatures, however that time decreases quite a bit if there's a strong wind blowing on the car.

 

[sauce]

Hey folks, interesting thread. Here's another question related to this.

My parents and in-laws currently only have 110v outlets at their homes and when visiting during winter, temperatures may drop below -20C.

Obviously I will want the car plugged in out of caution, but wouldn't need to actually recharge at their homes. Question is, would a 15A/110V plug be a sufficient power outlet to allow the battery heater to protect the battery in case of -20C to -30C temperatures or must I opt for installing a 14-50 plug at their homes?

I will get the same problem when visiting customers daily during the coldest winter days and cannot plug in at all or at best into a 110V outlet.

 

[kort677]

Hey folks, interesting thread. Here's another question related to this.

My parents and in-laws currently only have 110v outlets at their homes and when visiting during winter, temperatures may drop below -20C.

Obviously I will want the car plugged in out of caution, but wouldn't need to actually recharge at their homes. Question is, would a 15A/110V plug be a sufficient power outlet to allow the battery heater to protect the battery in case of -20C to -30C temperatures or must I opt for installing a 14-50 plug at their homes?

I will get the same problem when visiting customers daily during the coldest winter days and cannot plug in at all or at best into a 110V outlet.

this is a weak response but having the car plugged in would be far better than not having it plugged in