So… Highland is out…

[GeorgeSymonds]

The current/heat issue in the ancillary components is mitigated with thicker conductors so it’s not a bottleneck. The bottle neck has and will always be the cells. Everything else around it can just be built to a higher spec.

I think what you mean to say is you can mitigate with thicker conductors and components but in practice there is still one significant pinch point, the CCS connector itself. A quick google suggests its limit is 500A which Tesla are already exceeding to reach 250kw, but since when did Tesla ever follow standards? They probably get away with it by quickly reducing the rate after a short period of time based on the temperature of the plug/socket.

The point is, its unlikely anyone else is going to make a car that will happily charge above 500A on CCS because they'll comply with standards and interoprability, and so it's a 200kw limit at 400v - which is pretty much where they all top out at now. And at 800v, they can reach 350kw and be within the 500A limit.

 

[qwickshot]

Yes the CCS connector is the obvious elephant in the room.

That said, the cars that top out at 200kw do so for seconds, the limit is still the cells.

The new S and X can hold 250kw for longer but it’s still not that long in reality before it’s throttling back.

The same goes for the 350kw cars, the can hold the speed for a few seconds in outright optimal conditions before throttling back the the point where 400v/800v doesn’t really matter. It’s rare you even see a 800v Kia/Hyundai even get to optimal conditions because of the lacklustre software and the heating/cooling set up then have.

So many cars have throttling issues when rapid charging if you also have the HVAC running for the cabin.

 

[bkp_duke]

The rumor is Tesla will skip 800V entirely, for 1000V. That's at least what has leaked about the Cybertruck. Now, when that will get implemented to all the other cars, who knows.

 

[GlynG]

Would be nice to see some lower capacity 800V pack cars, with decent heat pumps for winter range.

Lighter should mean a bit more range, cost a little less and when you need to charge they're very quick.

The heat pumps for greater range in the colder temperatures only really produce a greater range if you travel on long drives, majority of people use their cars to drive to work daily and majority of people travel less than 30 miles to work and in these cases the heat pump is a lot less efficient than a resistive heater.
Just sticking to Tesla's resistive heater and their Heat pump to explain this. -

The resistive heater is 400 volts and 6.5Kw - so 16.25 amps, Instant heat produced and the only noise is the fan driving air through the heating elements direct into the cabin, once the cabin is at the desired temperature the heater modulates to hold the temp - so is replacing heat losses and it continues to do this for the whole journey.

Heat pump - which isn't just a solitary device as its part of the super manifold, the refrigerant lines, the 6 solenoids and 6 sensors plus two pumps - all built into the super manifold assembly with the heat pump part directing the flow of heat from the other components towards the heater matrix.
Tesla claim a total of 16 heat sources that contribute to the generation and transfer of heat to the cabin, majority of the heat produced though is by the motors and their inverters, other sources are minuscule production like the heat generated by the blower fan motor though they are totally recovering otherwise heat lost.
On a long drive the heat pump assembly is taking heat as a by product from the inverters and motors - so its free of consuming additional power from the HV battery - so in those circumstances the heat pump cars are more efficient and will have a greater range.

On short journeys though the heat has to be artificially generated and this is done by detuning the efficiency of the inverters and motors - its known as a "lossy" signal, this makes the efficiency of the components to plunge and it draws a lot of power from the HV battery, a dual motor car will take over 7.5Kws and its transfers heat to the refrigerant which is then pumped to the heater matrix inside the car, The motor windings are being used like a resistive heater but is less efficient as the heat is drawn away by the transfer process to refrigerant and then pumped along lines via the super manifold before being directed to the heater matrix - and there are heat losses within the lines. So, on short journeys a heat pump system draws more current from the HV battery and in comparison to a resistive heater is a lot less efficient.

For me thinking outside of warranty - replacement of the super manifold, its pumps, solenoids and sensors, the refrigerant lines and the heat pump drive motor would be an horrendously expensive repair in comparison to a simple resistive heater element or assembly, plus, a resistive heater is so reliable its likely never to fail and the most common cause of a failure is because the fan motor breaks and without the cooling air flowing over the elements the elements get too hot and burn out.

So its not a clear cut case of heat pumps are better, they are better in certain circumstances.

 

[bkp_duke]

The heat pumps for greater range in the colder temperatures only really produce a greater range if you travel on long drives, majority of people use their cars to drive to work daily and majority of people travel less than 30 miles to work and in these cases the heat pump is a lot less efficient than a resistive heater.

Source please. That's not been my experience. Our 2020 Y (heat pump) is efficient all the time, even in short trips in the cold. Our 2018 3 (resistive heater), not so much.

 

[bkp_duke]

For me thinking outside of warranty - replacement of the super manifold, its pumps, solenoids and sensors, the refrigerant lines and the heat pump drive motor would be an horrendously expensive repair in comparison to a simple resistive heater element or assembly, plus, a resistive heater is so reliable its likely never to fail and the most common cause of a failure is because the fan motor breaks and without the cooling air flowing over the elements the elements get too hot and burn out.

The failure rate of these is near zero. I had my car in for service 2 weeks ago (busted a strut - BAD potholes), and got to chatting up the tech working on my car about this. He had been with Tesla for 6 years. He says in that time this shop, one of the busiest in SoCal, had only ever replaced one heatpump.

 

[Jason71]

The heat pumps for greater range in the colder temperatures only really produce a greater range if you travel on long drives, majority of people use their cars to drive to work daily and majority of people travel less than 30 miles to work and in these cases the heat pump is a lot less efficient than a resistive heater.
Just sticking to Tesla's resistive heater and their Heat pump to explain this. -

The resistive heater is 400 volts and 6.5Kw - so 16.25 amps, Instant heat produced and the only noise is the fan driving air through the heating elements direct into the cabin, once the cabin is at the desired temperature the heater modulates to hold the temp - so is replacing heat losses and it continues to do this for the whole journey.

Heat pump - which isn't just a solitary device as its part of the super manifold, the refrigerant lines, the 6 solenoids and 6 sensors plus two pumps - all built into the super manifold assembly with the heat pump part directing the flow of heat from the other components towards the heater matrix.
Tesla claim a total of 16 heat sources that contribute to the generation and transfer of heat to the cabin, majority of the heat produced though is by the motors and their inverters, other sources are minuscule production like the heat generated by the blower fan motor though they are totally recovering otherwise heat lost.
On a long drive the heat pump assembly is taking heat as a by product from the inverters and motors - so its free of consuming additional power from the HV battery - so in those circumstances the heat pump cars are more efficient and will have a greater range.

On short journeys though the heat has to be artificially generated and this is done by detuning the efficiency of the inverters and motors - its known as a "lossy" signal, this makes the efficiency of the components to plunge and it draws a lot of power from the HV battery, a dual motor car will take over 7.5Kws and its transfers heat to the refrigerant which is then pumped to the heater matrix inside the car, The motor windings are being used like a resistive heater but is less efficient as the heat is drawn away by the transfer process to refrigerant and then pumped along lines via the super manifold before being directed to the heater matrix - and there are heat losses within the lines. So, on short journeys a heat pump system draws more current from the HV battery and in comparison to a resistive heater is a lot less efficient.

For me thinking outside of warranty - replacement of the super manifold, its pumps, solenoids and sensors, the refrigerant lines and the heat pump drive motor would be an horrendously expensive repair in comparison to a simple resistive heater element or assembly, plus, a resistive heater is so reliable its likely never to fail and the most common cause of a failure is because the fan motor breaks and without the cooling air flowing over the elements the elements get too hot and burn out.

So its not a clear cut case of heat pumps are better, they are better in certain circumstances.

You make some good points, though of course we mainly care about efficiency on long journeys so there is that.
And its not like the coolant/heat pipes to the motors and battery were added for this purpose they were always there its just that they have all been joined together to more efficiently share heat / cooling between them so I am not clear in practice how much more complex the heat pump setup is than what went before.
I do agree though I don't want to be the one holding the car when the manifolds start to pack up. I wonder how much replacement costs? I have never heard it mentioned maybe due to the fact that thus far they seem pretty reliable. Given how it seems that insurance company's seem to want to right off cars for the slightest tap these days there should at least be a good supply of used ones when they do start to pack up in numbers out of warrantee.

edit
anywhere from £250-£1250 on ebay

 

[Drew57]

Charging speed is also affected by the size of the pack. Make the pack lower capacity and it’ll also charge slower. This is why a Model S on a 100kWh can charge as quick as the Model 3 / Y’s on roughly 20kWh less. If you convert it to miles charged per hour the Model S is quicker.

This all assumes the car and not the charger is the limiting factor.

I didn't know that - I had always assumed that it was slower to charge because when I use a SuC & there is a Model S charging it almost always stays in situ for the duration of my charge & is still there when I leave (I normally average 35-40 minutes). On a Type 2 charger I've avoided taking the paired stall next to one for this reason, unless all others are in use.

 

[FastLaneJB]

Yes the CCS connector is the obvious elephant in the room.

That said, the cars that top out at 200kw do so for seconds, the limit is still the cells.

The new S and X can hold 250kw for longer but it’s still not that long in reality before it’s throttling back.

The same goes for the 350kw cars, the can hold the speed for a few seconds in outright optimal conditions before throttling back the the point where 400v/800v doesn’t really matter. It’s rare you even see a 800v Kia/Hyundai even get to optimal conditions because of the lacklustre software and the heating/cooling set up then have.

So many cars have throttling issues when rapid charging if you also have the HVAC running for the cabin.

Yes I must confess I'm not sure we really need faster chargers than 250kw though seeing as 350kw is possible won't complain. What we need is cars that can charge at that speed for more of the time or ideally if the battery chemistry ever allows it, all of the time. That's about 20 minutes to fill a Model 3 from 0 to 100 at 250kw. People won't rock up completely empty and not everyone will need to charge to 100% either so you probably have an average of people charging for around 10 minutes per stop.

I think that kind of turn around would be very acceptable. Filling an ICE car, going to pay for it is probably 7 - 8 minutes roughly.

Also good for the amount of chargers you need again. You've gone from a charger being able to do 2 cars roughly an hour to 6.

 

[Jason71]

I didn't know that - I had always assumed that it was slower to charge because when I use a SuC & there is a Model S charging it almost always stays in situ for the duration of my charge & is still there when I leave (I normally average 35-40 minutes). On a Type 2 charger I've avoided taking the paired stall next to one for this reason, unless all others are in use.

It probably has free supercharging and is charging to 100% which is slow.

 

[FastLaneJB]

It probably has free supercharging and is charging to 100% which is slow.

Older Model S’s did charge much slower, older tech than what they have in the 3 / Y. They really improved the charging speed when they came out with the Palladium models which are only LHD here.

For reference see this link. 20 to 80% charge on Model S is within 1 minute of a Model 3 LR yet the battery is larger. Bigger battery = faster charging speeds.

https://insideevs.com/news/515641/tesla-models-plaid-charging-analysis/

 

[GlynG]

The failure rate of these is near zero. I had my car in for service 2 weeks ago (busted a strut - BAD potholes), and got to chatting up the tech working on my car about this. He had been with Tesla for 6 years. He says in that time this shop, one of the busiest in SoCal, had only ever replaced one heatpump.

I have no idea on the failure rate of either the resistive heaters or the heat pumps - all i do know is that the heat pump is currently on revision 5 and that in the UK there has been some issues published on Tesla forums regarding the heat pump - though I don't know any details.

Regarding your last reply to my post - you wanted the source of my information regarding heat pump operation - just found the article and will attach, over an hour but its superbly riveting to watch and learn.

 

[LiamPope]

The heat pumps for greater range in the colder temperatures only really produce a greater range if you travel on long drives, majority of people use their cars to drive to work daily and majority of people travel less than 30 miles to work and in these cases the heat pump is a lot less efficient than a resistive heater.
Just sticking to Tesla's resistive heater and their Heat pump to explain this. -

The resistive heater is 400 volts and 6.5Kw - so 16.25 amps, Instant heat produced and the only noise is the fan driving air through the heating elements direct into the cabin, once the cabin is at the desired temperature the heater modulates to hold the temp - so is replacing heat losses and it continues to do this for the whole journey.

Heat pump - which isn't just a solitary device as its part of the super manifold, the refrigerant lines, the 6 solenoids and 6 sensors plus two pumps - all built into the super manifold assembly with the heat pump part directing the flow of heat from the other components towards the heater matrix.
Tesla claim a total of 16 heat sources that contribute to the generation and transfer of heat to the cabin, majority of the heat produced though is by the motors and their inverters, other sources are minuscule production like the heat generated by the blower fan motor though they are totally recovering otherwise heat lost.
On a long drive the heat pump assembly is taking heat as a by product from the inverters and motors - so its free of consuming additional power from the HV battery - so in those circumstances the heat pump cars are more efficient and will have a greater range.

On short journeys though the heat has to be artificially generated and this is done by detuning the efficiency of the inverters and motors - its known as a "lossy" signal, this makes the efficiency of the components to plunge and it draws a lot of power from the HV battery, a dual motor car will take over 7.5Kws and its transfers heat to the refrigerant which is then pumped to the heater matrix inside the car, The motor windings are being used like a resistive heater but is less efficient as the heat is drawn away by the transfer process to refrigerant and then pumped along lines via the super manifold before being directed to the heater matrix - and there are heat losses within the lines. So, on short journeys a heat pump system draws more current from the HV battery and in comparison to a resistive heater is a lot less efficient.

For me thinking outside of warranty - replacement of the super manifold, its pumps, solenoids and sensors, the refrigerant lines and the heat pump drive motor would be an horrendously expensive repair in comparison to a simple resistive heater element or assembly, plus, a resistive heater is so reliable its likely never to fail and the most common cause of a failure is because the fan motor breaks and without the cooling air flowing over the elements the elements get too hot and burn out.

So its not a clear cut case of heat pumps are better, they are better in certain circumstances.

Is that really how they work though?? I admit I haven't looked into the Tesla heat pump, but surely when it needs to produce heat it works like, well, a heat pump? Like the one in my house. Takes heat from the air which is a process that can provide heat something like 3-5 or more times more efficiently than resistive heating and is the whole point of heat pumps. Any heat it can extract from motors, electronics, etc would be just gravy on top. Why would they make a heat pump that doesn't work like a heat pump??

 

[Jason71]

Is that really how they work though?? I admit I haven't looked into the Tesla heat pump, but surely when it needs to produce heat it works like, well, a heat pump? Like the one in my house. Takes heat from the air which is a process that can provide heat something like 3-5 or more times more efficiently than resistive heating and is the whole point of heat pumps. Any heat it can extract from motors, electronics, etc would be just gravy on top. Why would they make a heat pump that doesn't work like a heat pump??

I would imagine so but when you are setting off in subzero temps and your cabin is freezing and so is your battery there probably is not enough heat to scavenge so it has to make its own but it does that using the rear motor to generate heat rather than a resistive heater.

 

[kelvin 660]

Well, I've had both a restive heater and heatpump model 3 and do mainly short journeys, and in my experience the heatpump version is 12.5% more efficient.
This data was based on my average kWh/mile over a one year period driving a similar mileage in both cars.

 

[LiamPope]

I would imagine so but when you are setting off in subzero temps and your cabin is freezing and so is your battery there probably is not enough heat to scavenge so it has to make its own but it does that using the rear motor to generate heat rather than a resistive heater.

Heat pumps don't need to scavenge heat from some warm electronics, nor produce it with resistive heating. They take it from the air, even if the air is sub-zero. That's what they do. They should always be more efficient than resistive heating. Like I said, haven't studied Tesla's implementation, but I'd be surprised if its fundamentally different.

 

[Adopado]

Is that really how they work though?? I admit I haven't looked into the Tesla heat pump, but surely when it needs to produce heat it works like, well, a heat pump? Like the one in my house. Takes heat from the air which is a process that can provide heat something like 3-5 or more times more efficiently than resistive heating and is the whole point of heat pumps. Any heat it can extract from motors, electronics, etc would be just gravy on top. Why would they make a heat pump that doesn't work like a heat pump??

It does work like a heat pump! If it takes heat that is being produced anyway you get a free bonus over just extracting heat from cold winter air.

If you watch the full video linked above you will know how it all comes together. Given that the presentation is well over an hour of detailed information, with no wasted time, you are not going to get an equivalent explanation in a couple of paragraphs on a forum!

 

[Adopado]

Heat pumps don't need to scavenge heat from some warm electronics, nor produce it with resistive heating. They take it from the air, even if the air is sub-zero. That's what they do. They should always be more efficient than resistive heating. Like I said, haven't studied Tesla's implementation, but I'd be surprised if its fundamentally different.

It’s fundamentally different. Well it is and it isn’t. Obviously you are going to get more “cheap” heat if you can take advantage of warm sources rather than just taking heat out of cold air. Remember we’re not just talking about warming some air in the cabin we’re also warming a huge slab of freezing cold battery pack.

 

[Krash]

I have no idea on the failure rate of either the resistive heaters or the heat pumps…

My S resistive heater lasted 100k miles, but there were several revisions to that part since 2017, so looking at old parts isn’t necessarily indicative of more recent parts. Newer parts may be much more solid.

 

[GlynG]

Heat pumps don't need to scavenge heat from some warm electronics, nor produce it with resistive heating. They take it from the air, even if the air is sub-zero. That's what they do. They should always be more efficient than resistive heating. Like I said, haven't studied Tesla's implementation, but I'd be surprised if its fundamentally different.

But Liam, the video was specifically about Tesla's implementation of what they call the heat pump / super manifold so I don't understand when you say you'd be surprised if its fundamentally different (to what you think). It isn't a air source or ground source heat pump so you cant really compare it to those systems.

What was presented is the facts, with all the components of the Tesla system laid out and explained just how they all work together When I watched that video it took me well over two hours because i was pausing whilst i took everything in, i needed to absorb it and understand before moving on, I found it all fascinating but I've always been into the minutia of how things work.

Now given the facts that below 10 degrees the heat pump consumes well over 7.5Kws to generate heat you can understand why Tesla added an extra 7KWhrs to the HV battery size - they had to demonstrate the Heat Pump provided additional range - without the extra 7Kwhrs then there is little in it. Bear in mind its an American car, people in the states tend to nip out to see a friend 200 miles away and think nothing of it, here in the UK we have much shorter journeys - so the American experience of the Heat Pump will be a lot different to ours.

The only thing I don't know is how long the lossy generation operates for and how well the inverters and motors naturally generate heat as a by-product of being used, but no matter what people say - on short cold runs the heat pumps consume more power than the resistive heater, on long runs the heat pump is more efficient.