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Heat Pump Limit?

So I was wondering how the heat pump would perform in extreme cold and today I got to find out.
E7DDE952-4EA1-42EB-A289-A0ADA426ADB1.jpeg


I put on about 200 kms today and while I was driving around the city the heat worked as expected, it kept us toasty warm. However, this evening I went out on the highway and the combination of -35 C and highway speed winds was too much for the heat pump. After about 10 minutes on the highway it started blowing cool air. This is obviously not ideal in Canada. We’ve had a nice winter this year but last January it was -40 the entire month. I’m hoping that the heat pump can be tweaked via firmware to steal some more heat from the battery (although that’s likely bad for the battery). We have an ICE car as a backup but ppl often ask me if the Tesla could be your family’s only vehicle. I’m not sure how to answer that if there is no heat in the highway for a good chunk of our winter.
 
So I was wondering how the heat pump would perform in extreme cold and today I got to find out. View attachment 634662

I put on about 200 kms today and while I was driving around the city the heat worked as expected, it kept us toasty warm. However, this evening I went out on the highway and the combination of -35 C and highway speed winds was too much for the heat pump. After about 10 minutes on the highway it started blowing cool air. This is obviously not ideal in Canada. We’ve had a nice winter this year but last January it was -40 the entire month. I’m hoping that the heat pump can be tweaked via firmware to steal some more heat from the battery (although that’s likely bad for the battery). We have an ICE car as a backup but ppl often ask me if the Tesla could be your family’s only vehicle. I’m not sure how to answer that if there is no heat in the highway for a good chunk of our winter.

Did you happen to see (through the app or SMT or having a thermometer) how cold it got in the car? Also, is this an dual or single motor?
 

dmurphy

Active Member
Supporting Member
maybe your blower heater is broken? even if the heatpump struggels your blower heater should heat the cabin just fine. in fact, in the old days it wasnt software limited to 28C. On HI it could heat the cabin to well over 50C. Theres a funny test with bjorn nyland and one of his mates having a sauna session inside a model 3.

There isn’t a PTC heater in the heat pump 3 or Y. Doesn’t exist.
 
Not too surprised, there's only so much heat the pump and the resistor could produce and it's hella cold outside! Even gas cars can feel cool at this temperature if you've got a small 4 banger, that's why up north a lot of people end up putting a piece of cardboard in front of the radiator to block off some of the airflow.

OP how's the charging speed and range at this temperature? Also could you try recirculate? Probably just fog/freezes up the windows in a minute or two in that weather I suppose..
 
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dmurphy

Active Member
Supporting Member
what.... no simple heater at all?? doesnt the heat pump have a rampup time? I.e. in the old model 3 you set it to high and immediately you get superhot air? thought heat pump takes 5-10min to even heat up properly?

Nope, it’s all heat pump. The pump works fairly quickly when there’s heat in the air to extract but at -25C (-12F) - it’s way below the balance point. The motors can run out of phase to generate waste heat, and then the pump can scavenge heat from the battery ...But no, no PTC heater.
 
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stopcrazypp

Well-Known Member
Dec 8, 2007
13,094
9,420
So I was wondering how the heat pump would perform in extreme cold and today I got to find out. View attachment 634662

I put on about 200 kms today and while I was driving around the city the heat worked as expected, it kept us toasty warm. However, this evening I went out on the highway and the combination of -35 C and highway speed winds was too much for the heat pump. After about 10 minutes on the highway it started blowing cool air. This is obviously not ideal in Canada. We’ve had a nice winter this year but last January it was -40 the entire month.
Given there have been a bunch of failures of the heat pump system (supposedly due to some sensors), I wouldn't be too sure it's not that instead.
2021 Model 3 heater not working
Did your heat return afterwards or in subsequent trips?

I’m hoping that the heat pump can be tweaked via firmware to steal some more heat from the battery (although that’s likely bad for the battery).
Even if the software is set to show that it's heating the motor/batteries or ideally even showing the kW split (including while it is charging), that would be quite helpful. Then it'll be easier to know if that's what is happening or if there is some other failure.
 
Given there have been a bunch of failures of the heat pump system (supposedly due to some sensors), I wouldn't be too sure it's not that instead.
2021 Model 3 heater not working
Did your heat return afterwards or in subsequent trips?

yeah, I don’t think it’s the commonly reported failure because as soon as I slow down to city speeds, 60km/h or so the heat comes back.

also, the other folks are reporting a warning popping up, aren’t they? I don’t have any warnings.

For the guy who was asking about battery in this cold, I definitely chewed through some today. I put on about 150 kms and went from 70% to 12%. I’m not too sure about charging in this cold, my garage stays a lot warmer than outside.
 

Matias

Active Member
Apr 2, 2014
3,860
5,435
Finland
There’s obviously a limit for the amount of heat a given system (in this case a heat pump) can produce (while staying within design specifications). Apparently you’re outside those limits.

But maybe Tesla could add that out of phase heat generation with motors to help.
 
Last edited:

SageBrush

REJECT Fascism
May 7, 2015
13,767
19,010
New Mexico
Brrrr.

I thought a heat pump at its worse works at a COP = 1
Perhaps the episode of cold air was a freezing event ?

OP:
The general idea of the car's operation in extreme cold *and* a cold battery is to provide heat to the pump via the coolant, itself heated up by running the motor(s) inefficiently. I'm not sure why that approach failed during part of your journey.

For longer trips, I think the car will have an easier time of it because Supercharging will add heat to the battery every stop.
 
Nope, it’s all heat pump. The pump works fairly quickly when there’s heat in the air to extract but at -25C (-12F) - it’s way below the balance point. The motors can run out of phase to generate waste heat, and then the pump can scavenge heat from the battery ...But no, no PTC heater.

doesnt the patent state the existence of two resistance heaters in heating mode 3?
 

dmurphy

Active Member
Supporting Member
doesnt the patent state the existence of two resistance heaters in heating mode 3?

The patent, yes. I haven’t seen anyone confirm they’re in the car yet, though. And either way, as I said, there’s no PTC heater for the cabin. The patent only included two low voltage strips for heating the coolant.
 
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