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Heat Pump Limit?

Cybr.Myk

Member
Aug 30, 2020
129
240
Saskatoon
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.
 

GZDongles

Member
Feb 23, 2020
225
289
Michigan
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?
 

Cybr.Myk

Member
Aug 30, 2020
129
240
Saskatoon
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?

it’s a dual motor Performance.

I should have checked the cabin temp but I try not to touch my phone when I’m driving. I can try tomorrow, it will be similar temperatures tomorrow as well.
 
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Candleflame

Active Member
Mar 9, 2015
3,318
1,791
QLD, Australia
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.
 

dmurphy

Supporting Member
Supporting Member
Dec 7, 2018
3,827
5,411
New Jersey - Morris County
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.
 

XPsionic

Member
Jan 20, 2021
79
110
los angeles
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

Supporting Member
Supporting Member
Dec 7, 2018
3,827
5,411
New Jersey - Morris County
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
10,978
6,088
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.
 

Cybr.Myk

Member
Aug 30, 2020
129
240
Saskatoon
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
3,447
4,153
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
12,576
16,656
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.
 

Saturday

Member
Jul 3, 2020
206
206
Maine
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?
 

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