stopcrazypp
Well-Known Member
Thanks for posting the follow up. Yeah, the rumormill is they are working on something that will permanently fix the issue, but currently the sensor swaps are only temporary fixes.
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Heat Pump Limit?
- Thread starter Cybr.Myk
- Start date
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- Tags
- heat heat pump winter driving
Uncle Paul
Well-Known Member
3 points.
1. It is good that Tesla has diagnosed the issue as a failed sensor, fixed it, and it should be working better now.
2. Tesla has only been installing these heat pumps for a short time now. Imagine they will continue working on them to make them even better.
3. When Elon was questioned, many years ago, on how his battery powered cars would be degraded at -40F, he cleverly replied that in -40F temperatures most ICE vehicles would not even start.
1. It is good that Tesla has diagnosed the issue as a failed sensor, fixed it, and it should be working better now.
2. Tesla has only been installing these heat pumps for a short time now. Imagine they will continue working on them to make them even better.
3. When Elon was questioned, many years ago, on how his battery powered cars would be degraded at -40F, he cleverly replied that in -40F temperatures most ICE vehicles would not even start.
Justin L
Member
I am having the same symptoms as the OP. Car gets quite chilly on the highway, but I can switch my commute to through the city and it maintains the temperature much better. Preheating works like a charm, but the cabin seems to get cooler and cooler as I drive home if I take the highway route. Once you get a chance to test it out, report back if the sensor fix did the trick as I'm sure I'll need whatever solution you get.
Ambient temperature is very important in this conversation. Maybe the sensor issue causes another car to have issues, but since you're in Alberta and it's been -25 to -35c all week, maybe you're discovering the upper limit of how much heat the heat pump could generate?
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.
Ah, the closest one is over an hour away. It would not start to precondition within my normal commute. I don’t get close enough. I could put it in track mode, I suppose. I don’t think I will but I think that’s another way to get it to heat up the battery.
SageBrush
REJECT Fascism
OK in terms of heating the battery, but the question is -- would it stop scavenging heat from the battery ?
Is #3 actually true? I have only been in -30F for a few days at a time. My 1997 Honda Civic at the time struggled to crank, but it did eventually start and drove fine (I idled it for 20 minutes first to be on the safe side).
TheRFMan
Member
Choose a nearby supercharger. You don't actually have to go there
Unfortunately, the nearest Supercharger to Saskatoon is 120km away. I highly doubt it would preheat from that far away.
If a PTC heater was still in the car to heat the cabin why bother with the heat pump? Well you might say that the PTC heater is a backup in case the heat pump can't produce enough heat. The problem is that Elon doesn't work that way. His thing is "In the case of designing a car, it means the need for every part is questioned. And again as Musk likes to say “the best part is no part the best process is no process."
He is not going to leave a PTC heater in the car when the heat pump is suppose to replace it. Yes, we might disagree but that's how he operates.
Yes - turning climate on from the app will actively heat both the cabin and the battery when all of the doors are closed. Opening a door will cause it to stop heating the battery. Using Keep Climate On from the touch screen will also actively heat the battery. I think, but I don't remember for sure, that the active heating target for the battery is 20 - 25C. The active heating target when navigating to a Supercharger is 50 - 55C. At 20C, most regen is available.
But again, you will spend more energy heating up the pack than you will gain from increased regeneration. One exception might be if you are starting your trip at the top of a mountain, in which case you might break even. The most efficient way of operating is to preheat only long enough to warm up the cabin, then adjust your driving to maximize the limited regen and minimize brake use (anticipate stops long in advance).
It seems like the compressor for the heat pump has the ability to operate in an inefficient mode to generate heat just like the drive motors. That's the backup. So not a direct PTC heater, but there is a way to actively generate heat to supplement what the system is able to scavenge from outside air.
there's a reason residential heat-pumps include a gas furnace / auxiliary electrical heating units ... because once you go below 30F it becomes *really* hard to heat the place via a heat pump ... under 25F nearly impossible...
iwannam3
Active Member
How much heat could a heat pump pump if a heat pump could pump heat? Apologies to the wood chucks out there.
Cleo-n-Company
Member
So as a clueless Californian, I am wondering... what does -36 feel like ?
Is it painful just to stand outside ? Can you actually feel the difference between - 20 and -30 for example ? Does the family dog just sit inside for a month or two ?
stopcrazypp
Well-Known Member
My understanding is that the heat pump still functions even at low temperatures, just that the COP is more like 1, which makes it so the heating capacity is well below what the user is typically expecting from the system (basically it'll never be able to reach the set temperature in the thermostat). So Aux heat (usually resistive) comes in to supplement. It's not that there is zero heat being generated.
In this case, the OP's issue was a defective sensor like most cases. So we have yet to see the true limits of Tesla's heat pump system (which as others point out has other ways to provide supplement heat).
Edit: someone in other thread provided EPA link that provides a very good description of how Tesla's production heat pump system works. On page 9 it addresses the issue of aux heat (bolded part about using the compressor as a substitute for a PTC heater):
Just finished my first "road trip" and I am not happy with range
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tstolze
Member
^^^^This ^^^^^
Newer Heat pumps can produce heat at or below zero and still be as efficient as resistive heating, then you take the heat that it has access to from 1 or 2 drive motors, the battery, and the compressor itself, while I believe isolating the transfer fluid from the radiator.
There's no heat to be had from the battery and motors when driving at -35c, in fact the heat pump has to do double duty and heat up the battery as well as the cabin.
tstolze
Member
You’re both right.
The system can scavenge heat from the motors and battery if they contain enough heat. If they don’t (-30C cold start, for example), the compressor must generate heat for both the cabin and the battery pack at a COP of 1, the same as resistive heat in non-HP cars.
Justin L
Member
Below -25°C it gets really hard to feel any difference. There's very little moisture in the air, so the heat loss in a "dry" cold helps a bit. At -25°C I can start to feel my nostrils stick a bit when I'm breathing through my nose. If you're dressed well, generally you stay pretty warm, but any exposed skin hurts, it's not a cold feeling per se, it just hurts. The colder you go and windier it gets the faster it hurts. You can get into trouble if it stops hurting, that means it's starting to freeze and it's time to deal with it. With good gear, it can be a lot of fun to go skiing or biking, but there's no half assing it with the gear. Everything has to be covered.
One other really interesting thing is the way planes sound going overhead. With no moisture in the atmosphere to attenuate the sound, you get a much higher pitch to a jet engine and it sounds more like it's ripping it's way through the sky.
