Cold weather driving sucks up the battery

[Zacster]

Not that this is news to anybody, but driving an SR+ in the cold weather we just had sucks up the battery. I went from 220 miles down to under 100 from doing 4 10 mile trips. I guess the car never gets a good chance to warm up with that kind of driving. Temps were in the single digits F with strong winds like a lot of the country.
I also tried to charge it in the cold with no time to pre-condition the battery and that was also super slow.

After a few days up in Syracuse, NY (thankfully not Buffalo) I drove back to NYC with temps in the mid 20s and the usage pretty much sucked there too but wasn't as bad as driving around Syracuse. We made more charging stops than I would normally because I couldn't get a good sense of range since the stated range was useless. Wh/Mi was in the 260-280 range, usually I get 220-230 on the highway in better weather, and 180-200 around town.

The good news to me was that the car handled pretty well on the icy/snowy roads.

 

[Kimmi]

It was 82 degrees here today.

 

[ATPMSD]

Wh/Mi was in the 260-280 range, usually I get 220-230 on the highway in better weather, and 180-200 around town.

It is really not too bad. I live in Atlanta and in my MS I typically see 280 Wh/mi., this week when it was single digits I saw nearly 400. Keep in mind that my MS has resistant heating, not a heat pump, and that accounted for probably 100 Wh/Mi. Subtracting that would have put me back at around 300.

 

[cappo3]

It is really not too bad. I live in Atlanta and in my MS I typically see 280 Wh/mi., this week when it was single digits I saw nearly 400. Keep in mind that my MS has resistant heating, not a heat pump, and that accounted for probably 100 Wh/Mi. Subtracting that would have put me back at around 300.

I’m not sure the heat pump makes that kind of difference, in the best of conditions. On top of that you were probably driving in less than best conditions for a heat pump.

 

[AAKEE]

I’m not sure the heat pump makes that kind of difference, in the best of conditions. On top of that you were probably driving in less than best conditions for a heat pump.

If the car has been parked outside and the battery is cold and the ambient also is cold enough, like -10C or colder the heat pump doesnt really have any heat to scavenge. Then it`s a close call between heat pump and not H.P.

Having the car inside, and recently charged it’s a big difference to the advantage of the heat pump car.

Having Supercharged and driving after that, it’s possible to drive for one hour or 1 1/2 at very low ambient temps and still have consumption almost like in the summer.

 

[cappo3]

If the car has been parked outside and the battery is cold and the ambient also is cold enough, like -10C or colder the heat pump doesnt really have any heat to scavenge. Then it`s a close call between heat pump and not H.P.

Having the car inside, and recently charged it’s a big difference to the advantage of the heat pump car.

Having Supercharged and driving after that, it’s possible to drive for one hour or 1 1/2 at very low ambient temps and still have consumption almost like in the summer.

I'm not yet entirely convinced by the large advantages attributed to the heat pump.
I remember, in the beginning, the HP cars where scavenging so much heat from the batteries that the performance ended up being restricted in colder weather. That's because you need quite some energy to heat up the whole cabin and battery heat simply isn't enough most of the time.
After a Supercharging session, or generally with a very warm battery (I don't think parking inside in winter is enough for that to happen), I'm sure there in fact is enough heat to scavenge, as you say.
Apart from the scavenging scenario, where the Octavalve should excel, I don't see how Tesla's heat pump should be so much more efficient than, for example, VW's implementation. They had to cut the HP option price in half and compensate existing customers because it wouldn't increase general efficiency in the measure they had stated. It was quite the debacle for them, that one.
For what I know, Tesla did not reinvent the heat pump technology. This is my opinion, after reading extensively about the matter.
Moreover, based on my empirical, personal and therefore completely anecdotal experience, driving two otherwise nearly identical vehicles on a regular basis and on the same stretches of road (78k miles in the 2020 car and 35k miles in the 2021, crossing the Alps between Switzerland/Austria and Italy), while I surely welcome the HP, it's not something I'd have to have in my next vehicle.

 

[ATPMSD]

While Tesla has done some neat things to make their HP work in the cold, HPs do not work well in cold weather. This is why in most homes that have a HP there is also a resistance heat system that kicks in on very cold days. It is really too bad Tesla did not leave the resistance heat system in the car, which would have offered the best of both worlds.

 

[Braumin]

The heat pump only works down to -10°C (14°F) as far as scavenging heat from the outside. After that it uses the heat from the compressor to generate heat.

Was on the highway on Saturday. It was -20°C (-4°F). Round trip of about 150 km was 300 Wh/km or 480 Wh/mile. Short trips can even be worse for consumption when it's really cold.

 

[AAKEE]

I'm not yet entirely convinced by the large advantages attributed to the heat pump.
I remember, in the beginning, the HP cars where scavenging so much heat from the batteries that the performance ended up being restricted in colder weather. That's because you need quite some energy to heat up the whole cabin and battery heat simply isn't enough most of the time.

I have a M3P 2021 with heat pump since exactly two years, 56K km and live in a very cold climate.
Yes, in general Tesla took too much energy from the battery in the beginning. They fixed that, so now the heat pump operates between 13 and 18C batt temp. At low SOC the car
Tesla also had an extra power limitation on the new 2170L cell. They changed that also during the spring of 2021.
It okey now, not very weak at low SOC anymore.

After a Supercharging session, or generally with a very warm battery (I don't think parking inside in winter is enough for that to happen), I'm sure there in fact is enough heat to scavenge, as you say.

I have logged data on this.
I only have around 10C in the garage, if I start with the battery at 10C and it is colder than -10C outside, there is not enough energy on a short drive to heat the cabin.
During long drives, the battery heat itself to 17-18C, then the heat pump use the heat to heat the cabin, the battery heat is used down to 12C batt temp. The consumption is noticable lower when this happens.

A drive to the neighbour town on AP/cruise control took /km at -15 the other week took 200 Wh/km with a recently charged battery that was 23C (charged with 11kW at home) and a few days later with a battery that was not recebtly charged and was 9C, the same trip/same temp took 200Wh/km.

I domis a 240km drive that was at -20 axfewzdays ago. I charged at home to 99%, so the batt temp was 25.8C at the start of the drive.


After 45 minutesthe batt temp was 11.8C and the heat pump stopped scavengint from the battery. At that point the consumption was 201 Wh/km.

After another 90 minutes the batt temp was 18C and the consumption 230 wh/km and the heat pump started using battery heat again.


I arrived at the destination with batt temp 13.3C and 215 Wh/km for the complete drive.

Apart from the scavenging scenario, where the Octavalve should excel, I don't see how Tesla's heat pump should be so much more efficient than, for example, VW's implementation.

The heat pump itself is probably a regular one. Its the octovalve that makes it briljant, to be able to receive or send heat from the motors, battery, cabin and outside air.

We can see in tests how much more energy EV’s use in winter time in a lot of tests in Scandinavia. Its clear that Tesla is in top, even if they let the cars cold soak before the tests ( in clear opposite to using this technology the best way, like charging shortly before the drive or supercharge to use the excess heat to get very low consumption.)

 

[AAKEE]

The heat pump only works down to -10°C (14°F) as far as scavenging heat from the outside. After that it uses the heat from the compressor to generate heat.

It also use the excess heat from the battery and motors, this is the absolute best part.
But it of course presupposes that there is any heat to use.
If the battery is warmer than 12C, that excess heat will be used down to 12C (from whatever cell temp it had before).
After that it will let the battery self heat from the drive to 17-18C, and then use the heat down to 12C again.

I charge late at night, or more to say in the morning and the charge is done so it is finished just before the drive. At home this means about 23-26C depending on the start and target SOC.
This is sufficient for 45 minutes drive in -20C (-4F) where the heat pump use batt heat instead of battery current to heat the car.
The consumption when using battery heat at below -10 to heat the cabin is somewhere 15-25% more than when using the heat pump after regular home charges.
After supercharging starting with the battery at 58C, the consumption is not much higher than at summer.

 

[Zacster]

By the time I need to drive the car again it'll be back in the 40s and then the 50s here in NYC.

And one thing I tried on the drive back from Syracuse was turning off the cabin heat. It helped as I could see the usage drop some, maybe 10-15 wh/mi, not enough to compensate for my wife complaining that it was cold though. I had done this while driving by myself around Brooklyn last winter at typically low speeds and it was very effective. At high speeds though the car just got cold really fast.

 

[hakunamattata]

Not that this is news to anybody, but driving an SR+ in the cold weather we just had sucks up the battery. I went from 220 miles down to under 100 from doing 4 10 mile trips. I guess the car never gets a good chance to warm up with that kind of driving. Temps were in the single digits F with strong winds like a lot of the country.
I also tried to charge it in the cold with no time to pre-condition the battery and that was also super slow.

After a few days up in Syracuse, NY (thankfully not Buffalo) I drove back to NYC with temps in the mid 20s and the usage pretty much sucked there too but wasn't as bad as driving around Syracuse. We made more charging stops than I would normally because I couldn't get a good sense of range since the stated range was useless. Wh/Mi was in the 260-280 range, usually I get 220-230 on the highway in better weather, and 180-200 around town.

The good news to me was that the car handled pretty well on the icy/snowy roads.

I also drove along the same route around the same time, just curious if your car was trying to constantly pre-condition the car for supercharging? In my case I saw the car trying pre-condition when the next supercharger was over 150 miles when I had already charged and driven for over 100 miles. The temperature was around 40F with a feels like temp around 35F

I saw this pre-conditioning increase my consumption to over 350 wh/mi.

 

[Zacster]

Yes. I had to turn off the navigation because of it. And now that I think about it I haven't left it on since. In NYC I never use the NAV anyway but on the road I do because of the chargers.

Another frequent problem is that I'll have a full charge leaving Brooklyn and it'll send me to the SC in New Jersey somewhere before I've even gotten going. It also sent me once to downtown Manhattan somewhere, the last place I'd go to charge.

 

[hakunamattata]

Yes. I had to turn off the navigation because of it. And now that I think about it I haven't left it on since. In NYC I never use the NAV anyway but on the road I do because of the chargers.

Another frequent problem is that I'll have a full charge leaving Brooklyn and it'll send me to the SC in New Jersey somewhere before I've even gotten going. It also sent me once to downtown Manhattan somewhere, the last place I'd go to charge.

Thanks for your response, I wanted to make sure it was not just me as I was driving a brand new model Y in the extremely cold weather around Buffalo and Niagara on the Canadian side

 

[STS-134]

Not that this is news to anybody, but driving an SR+ in the cold weather we just had sucks up the battery. I went from 220 miles down to under 100 from doing 4 10 mile trips.

Worst case scenario. The car is forever consuming a lot of energy to heat up the cabin, only for you to stop driving and let the cabin cool back down. ICE vehicles get horrible gas mileage if you do trips of < 5 miles even in the summer, because they're burning a lot of gas to heat the engine block.

 

[Zacster]

Worst case scenario. The car is forever consuming a lot of energy to heat up the cabin, only for you to stop driving and let the cabin cool back down. ICE vehicles get horrible gas mileage if you do trips of < 5 miles even in the summer, because they're burning a lot of gas to heat the engine block.

I figure it's the battery that doesn't get warmed up enough. The cabin is warmed in advance remotely.

 

[thesmokingman]

While Tesla has done some neat things to make their HP work in the cold, HPs do not work well in cold weather. This is why in most homes that have a HP there is also a resistance heat system that kicks in on very cold days. It is really too bad Tesla did not leave the resistance heat system in the car, which would have offered the best of both worlds.

Isn't that what the motor is there for??

 

[STS-134]

I figure it's the battery that doesn't get warmed up enough. The cabin is warmed in advance remotely.

If your battery is cold, you'll get a snowflake symbol next to the battery gauge and part of the gauge will appear blue, indicating that that amount of electricity is inaccessible due to cold. But the bigger issue is that you're using the battery to heat the cabin. If you are preheating the cabin in advance then you are using even more energy than it would take to heat it up after you get in the car.

 

[AAKEE]

I figure it's the battery that doesn't get warmed up enough. The cabin is warmed in advance remotely.

When you heat the cabin or get it preconditioned, the battery is heated if it is too cold.
A complete precondition (planned departure) heats the battery to about 6.5-7C*, which is not enough for the Heatpump to use heat from the battery. It is warm enough for the battery to be happy.

I did turn on the heat one week ago, the battery was recently charged so it was about 8-9C and the car connected to the net with the UMC and 2kW was set.
Usually I turn the heat on shortly before but this time I ended up drinking another cup of coffe so it was preheating for about 30 min.
The battery was heated to about 23-25C when I started the drive so in this case it was plenty of heat to use in the battery.

But as 2kW charging is not powerfull enough to heat the cabin, the car used a few percent of the state of charge as well if I remember it right.


*) Checked last winter, not yet this winter.

 

[ATPMSD]

Isn't that what the motor is there for??

As I said, Tesla did some neat things to help the HP work when the temperature gets very low, but given some comments, when it is very cold the heat from the motors does not appear to be up to the task. Interestingly, if the heat from the motors was in fact sufficient why would a HP be needed at all? The HP adds complexity and cost while simple using heat from the motors is free heat - just like the free heat from an ICE car engine.

So, good question!

BTW, I am referring only to the heat generation side of the HP; the HP also serves the very important role providing AC.