Heat Pump Limit?

[SageBrush]

I don't quite buy the mode 5 explanation since the higher speed would increase the heat generation in the battery. The higher speed could well reduce the coolant temperature though, and thus the heat pump COP.

If I am not mistaken though, the Octovalve is able to close the radiator circuit but continue circulating fluid between the cabin, motors, and battery.

 

[Big Earl]

I don't quite buy the mode 5 explanation since the higher speed would increase the heat generation in the battery. The higher speed could well reduce the coolant temperature though, and thus the heat pump COP.

If I am not mistaken though, the Octovalve is able to close the radiator circuit but continue circulating fluid between the cabin, motors, and battery.

It likely would have been in mode 4 at the start of the trip and switched to mode 5 to precondition for supercharging, at which point it’s splitting the available heat between the cabin and the battery.

 

[SageBrush]

It likely would have been in mode 4 at the start of the trip and switched to mode 5 to precondition for supercharging, at which point it’s splitting the available heat between the cabin and the battery.

OP did not mention pre-conditioning.

But even if he had, it would make sense for the system to activate the motors in inefficient mode and circulate the coolant between the motor(s), battery, and cabin. No coolant circulating in the radiator, so no higher speed effect.

 

[Big Earl]

Ah, yes. I’m getting threads mixed up.

Regardless, I don’t see any heating modes where the drive units actively heat via the inefficient mode like the non-heat pump Model 3. Instead, the heat pump uses that same strategy with its own motor. I’d love to see more data in this from folks who have ScanMyTesla.

 

[bpjod]

I don't quite buy the mode 5 explanation since the higher speed would increase the heat generation in the battery. The higher speed could well reduce the coolant temperature though, and thus the heat pump COP.

If I am not mistaken though, the Octovalve is able to close the radiator circuit but continue circulating fluid between the cabin, motors, and battery.

Ah yes, but you’ve forgotten about the whole underside of the car acting like a giant radiator for the battery. At -40C (-40F) and 80 km/h (50 mph) windchill is -67C (-89F). Now the OP was driving at 110 km/h (70 mph) which is even worse, but the table I referenced only went to 80 km/h. Think of how much heat that air moving under the car is stripping away from the batteries. Those batteries aren’t warming at all while driving.

I have an old Model 3 and I’ve driven all day on highways and the batteries never warmed up enough to accept a charge from a Supercharger any faster than at my home 40A charger. This was at -27C and prior to the preheating the battery when en route to a Supercharger update.

I bet the new heat pump simply can’t keep up with the demand in heating both the batteries and cabin at highway speeds in -40C temperatures. Don’t forget the windows are like radiators stripping heat from the cabin too.

It’s going to be going down to -42C tonight where I live, but no way am I going out in that to experiment, so don’t even think of asking. I’m staying inside, right here where I’m nice and toasty.

 

[LeffeP]

Here in Sweden we don't have those numbers on our termometer regularly, more around -10 C. I also notice a huge difference when driving in city conditions vs highway and some speed. Warm and toasty in the city, but noticeable colder after a few miles on the highway. Haven't gotten to the point when it blows only cold air, but if the temp drops more I'm sure it will. We have had some real mild winters the last few years, but there always a period with real cold, and having to freeze driving a 60K new car sucks... The heat pump may be a great solution, but the 2014 Model S i had was warm regardless of how low the temp was...

 

[SageBrush]

I’d love to see more data in this from folks who have ScanMyTesla.

Check out Bjorn Nyland on youtube. His series of cold weather tests are most excellent.

In addition to non-Tesla reports, he tests his 2018 Model 3P and a 2021 Model 3P

Here are Part I and Part II for the heat pump/Octovalve equipped 2021 Model 3

My impression is that Tesla currently is quite aggressive in using battery heat instead of battery energy for cabin heating. That works well for most use cases but corner cases are not uncommon, particularly for owners that do not know what is going on and plan accordingly. E.g., the battery heat is depleted down to 10C in winter conditions while driving. That is too low to get good DCFC rates. And if the owner reaches a destination and decides to charge the following morning rather than plug in immediately, the battery will charge really poorly, even on L2. Of course any generation Tesla will cold gate if the temperature is low enough; the change here is that the new models reach their destinations with battery temps lower than the older models.

I'll hazard a guess that the Tesla algorithm is poorly optimized for -40C although I don't yet understand the exact gotcha. I'll guess that OP could have avoided the poor cabin heating intervals by putting the car in battery pre-condition mode from the beginning of his day. That would have told the car to not scavenge heat from the traction battery, in effect changing his car to an older model 3.

 

[Zcd1]

...I'll hazard a guess that the Tesla algorithm is poorly optimized for -40C although I don't yet understand the exact gotcha.

Agreed.

 

[Cybr.Myk]

Service is on the way right now to take it for a nice long highway drive. I’ll let you know what they say.

 

[Cybr.Myk]

Apparently it is broken. The ambient temperature sensor that causes Model 3’s to have no heat is failing. It just hadn’t gotten to the point where it gave me a user facing warning yet. He said that this is something he has seen before where the vehicle has progressively less heat at highway temps and then eventually has no heat at all, even in the city. He was here Friday to check my blocked/blinded cameras (was just frost and even exhaust from other vehicles) but he didn’t see any thermal warnings (I had asked him to check) then when he arrived this morning he said he can now see thermal warnings on his system.

So it was broken, after all. Once he replaces the sensor it will be interesting to go for a highway drive and see what kind of a difference it makes. He is working on it now.

 

[Venom]

Apparently it is broken. The ambient temperature sensor that causes Model 3’s to have no heat is failing. It just hadn’t gotten to the point where it gave me a user facing warning yet. He said that this is something he has seen before where the vehicle has progressively less heat at highway temps and then eventually has no heat at all, even in the city. He was here Friday to check my blocked/blinded cameras (was just frost and even exhaust from other vehicles) but he didn’t see any thermal warnings (I had asked him to check) then when he arrived this morning he said he can now see thermal warnings on his system.

So it was broken, after all. Once he replaces the sensor it will be interesting to go for a highway drive and see what kind of a difference it makes. He is working on it now.

Glad to hear that it's due to the heat pump being broken and not a limitation of it! At least you'll be toasty warm when it's all fixed. Is it something he can fix in 1 day?

 

[Cybr.Myk]

Glad to hear that it's due to the heat pump being broken and not a limitation of it! At least you'll be toasty warm when it's all fixed. Is it something he can fix in 1 day?

It took him about 30 minutes or so to change out the sensor. He did say that he anticipates an entirely different part will be coming at some point but for now he could only replace the failing part with the same part.

 

[kgvickers]

If this was posted already, sorry, I missed it.

I see the problem may be resolved but this looks interesting: www.evinsulate.com

 

[Phlier]

I'll guess that OP could have avoided the poor cabin heating intervals by putting the car in battery pre-condition mode from the beginning of his day. That would have told the car to not scavenge heat from the traction battery, in effect changing his car to an older model 3.

I think you're on to something here, and might very well be what our frozen neighbors to the north might need to start doing. At least in the heat pump equipped models.

 

[Phlier]

It took him about 30 minutes or so to change out the sensor. He did say that he anticipates an entirely different part will be coming at some point but for now he could only replace the failing part with the same part.

View attachment 635058

Glad to hear it was an easy fix! There have been quite a few reports of this exact sensor not even being hooked up on quite a few European delivered Model 3's the last few months.

I'm sure that there's a few of us (well, at least *one* ) that is/are anxious to hear how the heat works for you now.

 

[Cybr.Myk]

I think you're on to something here, and might very well be what our frozen neighbors to the north might need to start doing. At least in the heat pump equipped models.

I feel like a total noob but how would I force it to do that without navigating to a supercharger?

 

[Venom]

I feel like a total noob but how would I force it to do that without navigating to a supercharger?

I don't think you can. Pre-heat pump people turned on the heating for 15-20 minutes to heat up their battery, but I have no idea what the effect is on battery temp with the heat pump.

You could just charge it for 15 mins before leaving.

 

[Big Earl]

I don't think you can. Pre-heat pump people turned on the heating for 15-20 minutes to heat up their battery, but I have no idea what the effect is on battery temp with the heat pump.

You could just charge it for 15 mins before leaving.

Preheating still exists on the heat pump cars. Just go to the app and turn on climate control on. The system will begin conditioning the cabin and the battery.

 

[Venom]

Preheating still exists on the heat pump cars. Just go to the app and turn on climate control on. The system will begin conditioning the cabin and the battery.

Oh really? So turning on climate control will condition the battery? I had no idea. I assumed the battery was heated up as a side effect of warming up the cabin.

 

[SageBrush]

I feel like a total noob but how would I force it to do that without navigating to a supercharger?

Choose a nearby supercharger. You don't actually have to go there

The car has its own pre-conditioning routine you cannot modify but if you get "close" to the supercharger by chance the battery heating will start. I'm guessing that even before that happens (if it happens), the car will stop scavenging heat from the battery.