Why does Tesla use a Resistance Heater instead of Heat Pump

[arnis]

I didn't expect Tesla to update their HVAC on Y but they did.
MP3Mike, mongo, StealthP3D who all "disagreed" with anything I said are switching sides unnoticeably

That "windings inefficiency blabla" is "inventing a bicycle" story. (PS: Google calls FSD computer "Autopilot", hmmm)
As a heavy HP user, I tell you guys, that at -12*C HP automotive compressor is running really hard and
using at least 1kW of electricity. That electricity "magically" turns into heat. So 1kW of energy used by compressor
will still be able to generate around 1.3-1.6kW of heat. In addition to PTC that will definitely still be available on Model Y.
If I worked at Tesla, I would still experiment with exhaust port(s) radiator(s) for heat scavenging. These ports are
behind the rear bumper for most vehicles. And of course use coolant from drivetrain as refrigerant "afterheater"
right after refrigerant passes external heat condenser and before it enters compressor in HEAT loop.

Like I said before I will say again. -20*C is rare - Wisconsin or Norway. No need to go crazy with optimization for these conditions.
Also air is very dry at these temps and heating requirements (per one extra degree) go down compared to -5*C.


As of right now Model Y should be "good performer" in cold climates. Compared to S or even 3 - those are "one of the worst".
Biggest Winter Range Test Ever Reveals Best EVs For Cold Weather

 

[MP3Mike]

In addition to PTC that will definitely still be available on Model Y.

Nope, there is no PTC heater in the Model Y.

 

[dgpcolorado]

Nope, there is no PTC heater in the Model Y.

Right, if the patent listed in Mongo's post 556 is the system used in the Model Y, no separate PTC heater is needed.

 

[mongo]

Right, if the patent listed in Mongo's post 556 is the system used in the Model Y, no separate PTC heater is needed.

It is also not listed in the HV components for the Y.

 

[TimothyHW3]

Will the heat pump also warm up the battery instead of the stators on the motors? This will not only decrease heat usage, but also greatly improve "standby drain", especially while driving to Supercharger or when preheating the car. The current Model 3 Dual Motor uses up to 7.5kW from both motors just to heat up the battery. This is huge if they can lower that!

 

[mongo]

Will the heat pump also warm up the battery instead of the stators on the motors? This will not only decrease heat usage, but also greatly improve "standby drain", especially while driving to Supercharger or when preheating the car. The current Model 3 Dual Motor uses up to 7.5kW from both motors just to heat up the battery. This is huge if they can lower that!

Yes, the more complex version called out in the patent does that.

 

[TimothyHW3]

Yes, the more complex version called out in the patent does that.

Is there a way to get a confirmation? Do we have someone with OBD II adapter and Model Y to tell us what happens with the stators when you preheat the car? That will be interesting.

I would assume they would use it to heat the battery but who knows? Is the heat pump very loud? I remember the Renault Zoe was very loud.

 

[MP3Mike]

Is there a way to get a confirmation? Do we have someone with OBD II adapter and Model Y to tell us what happens with the stators when you preheat the car? That will be interesting.

I imagine that Tesla will use whatever they feel is necessary. If you have a "frozen" battery and plug in at a Supercharger it will likely use both motors and the heat pump to get the battery up to charging temperature as quickly as possible. Is there a reason you don't want them to use the motors for heat? (If it is really cold the heat pump only operates at a COP of 1, so I doubt it would be any more efficient than the motors.

I would assume they would use it to heat the battery but who knows? Is the heat pump very loud? I remember the Renault Zoe was very loud.

It doesn't seem to be any louder than the AC system on the Model 3. There is a video on YouTube where someone turned it on and was outside to listen.

 

[TimothyHW3]

I imagine that Tesla will use whatever they feel is necessary. If you have a "frozen" battery and plug in at a Supercharger it will likely use both motors and the heat pump to get the battery up to charging temperature as quickly as possible. Is there a reason you don't want them to use the motors for heat? (If it is really cold the heat pump only operates at a COP of 1, so I doubt it would be any more efficient than the motors.

It doesn't seem to be any louder than the AC system on the Model 3. There is a video on YouTube where someone turned it on and was outside to listen.

The motors' stators are very inneficient. 7,5kW is a lot. If the heat pump runs at 7.5kW even at 1 COP it is still better than the stators. But most of the time it will be at least around 2. Also using the motors, it makes noise and while overall a good workaround, I would like a dedicated system that doesn't involve the stators for something other than driving to reduce the workload on the drive unit. It is still an expensive thing to repair.

Can you link me to the video with the noise test? What was the outside temp? It should be in your Youtube history or at least the channel name?

 

[MP3Mike]

The motors' stators are very inneficient. 7,5kW is a lot. If the heat pump runs at 7.5kW even at 1 COP it is still better than the stators.

How is the motor using 7.5kW to produce nothing but heat less efficient than the heat pump running 7.5kW at a COP of 1 to produce heat?
In both cases 100% of the electricity is getting converted into heat. (Maybe more of the heat gets lost into the environment from the motor casing and coolant lines, but I doubt it is a significant difference.)

Can you link me to the video with the noise test? What was the outside temp? It should be in your Youtube history or at least the channel name?

It is buried somewhere in this long video:

 

[TimothyHW3]

Because the heat pump will not use 7.5kW and in most cases will run at 2 -2.5COP.
When I said it is better at 1 COP I meant to say that I prefer the heat pump to run isntead of the complicated and expensive DU that is needed to move the car around.

Plus I am not quite sure wether the heat from the stators is at 1 COP, I am pretty sure there are more losses on the way to the battery.

Ok I heard it, but was on high - it was quite loud actually. I guess we have to wait and see.

 

[arnis]

Correct. Heating motors and then transporting heat has lots of losses on the way (especially when driving) and on the way back to motor. Also motor itself cools down (made out of metal). In case of those 'good ol' 0F cases' everybody is so happy to tell here, losses can be way more than 20%, depending on speed/wind.
This is why EVs with external cabin heating units have significantly lower efficiency (than 100%) compared to HVAC PTC units.
HP efficiency in real weather never drops to (or near to) COP1.0. It also depends on refrigerant that is used in the system and HP compressor design (how many stages of compression).

HP in heating cycle makes more noise than in cooling cycle (including fans) if load is equal (for example, 1kW).

 

[Lon12]

So I see from Munro's latest video that Model Y owners are already complaining about the noise of the heat pump and that Tesla will be installing a noise cover on it soon.

 

[AWDtsla]

So I see from Munro's latest video that Model Y owners are already complaining about the noise of the heat pump and that Tesla will be installing a noise cover on it soon.

The story here is Tesla shipped cars to customers with pieces missing. Surprise Surprise.

 

[mongo]

The story here is Tesla shipped cars to customers with pieces missing. Surprise Surprise.

May not be that simple, some Y are quiet:
Heat Pump Sound Issue?

 

[InternetDude]

The story here is Tesla shipped cars to customers with pieces missing. Surprise Surprise.

Nothing is more important to Tesla than delivery #s.

 

[arnis]

My eye-measurements say that cover was not planned. There is no space for 2-3cm cover over compressor. So they will have to "get creative" with that insulation.

 

[Candleflame]

Yes, so why is everyone treating this as an OR situation when it clearly could be a AND situation? Why doesn't the S have a heat pump? I'm not sure about everyone else but I use the heat all the time when its cold and not only is the S far more inefficient, it also doesn't heat as well as a lowly leaf. That's not good to be beaten by a car 1/3 the cost (before incentives, 1/5 after) in anything, much less heating.

I do believe this a california mindset still because those of us in the frozen north lose a bunch of our range to an inefficient heating system that draws 6kw of energy to provide less heat than my leaf which used 1.5kw.

I believe a lot of the reason is that Teslas are cars made by desert people for the desert. Didn't they mess up the initial headlight washers or smth because theyd freeze in the cold and the engineers didnt consider that. Tesla probably does attract some talent but I doubt many engineers are from cold regions.

A good example of the other way around are older BMWs in the desert - I know BMW usually tests their cars in the USA for heat and low quality fuel tests but certainly with the E46 3 series and the equivalent 5 series they didnt engineer the offgassing smell very well - not very pleasant lol.

 

[wws]

Well GM and Ford haven't used heat pumps either - and they are in Michigan. So go figure.

(Historical note: 25 years ago, GM did use a heat pump in the EV1.)

 

[Matias]

Heat pump solution is not without issues. More specifically apparently Tesla draws heat from the battery too much and it affects cold weather performance in the new Model 3 performance.