Wow, we need to find another way to heat EVs

[AlanSubie4Life]

I don't get why this is funny. But OK.

There just is not substantial heat available; I just thought that was a funny statement. And what little there is is scavenged to warm the battery up a little (which is not really sufficient in very cold conditions). It takes multiple kW to warm the cabin adequately! Where would that come from? At 80mph the car is only consuming 24kW - and nearly all of that is being converted into useful work!

 

[jpfive]

Mine draws between 3 to 3.5 kW when preheating the cabin. There’s also a noticeable buzzing coming from the rear end when this happens. Stator temperature of the drive unit increases when this starts, and you can see an increase in the battery inlet temperature as well indicating this heat is going to the battery.

The buzzing and power draw from the rear motor shuts off when I open the door, it doesn’t happen when I am sitting in the car. Just when the cabin is empty for some reason.

How was this file generated? Third party app?

 

[TomB985]

How was this file generated? Third party app?

Yep.

I use an OBD adapter wired into the car, and a Bluetooth OBD interface that connects it with my Android tablet. The "Scan my Tesla" app on the tablet interfaces with the car and reads the data.

Here's the hardware I use:

OBDII Adapters for Tesla Vehicles | GPS Fleet Tracking | Fleet Tracker

https://www.amazon.com/ScanTool-OBDLink-Bluetooth-Professional-Diagnostics/dp/B006NZTZLQ

 

[jpfive]

Yep.

I use an OBD adapter wired into the car, and a Bluetooth OBD interface that connects it with my Android tablet. The "Scan my Tesla" app on the tablet interfaces with the car and reads the data.

Here's the hardware I use:

OBDII Adapters for Tesla Vehicles | GPS Fleet Tracking | Fleet Tracker

https://www.amazon.com/ScanTool-OBDLink-Bluetooth-Professional-Diagnostics/dp/B006NZTZLQ

Thank you.

 

[BR666T]

I also have a heat pump at home.
It seems like the problem with putting a heat pump in the car would be the size. The radiators on efficient heat pumps are pretty large. The cabin heating and cooling requirements on a car are actually about the same as an apartment, 5kW = 17,000BTU.
The biggest problem with a heat pump may just be that it doesn't help EPA range.

As I pointed out earlier in this thread, Nissan has an available heat pump for the Leaf: Heat-Pump Cabin Heater

 

[Daniel in SD]

As I pointed out earlier in this thread, Nissan has an available heat pump for the Leaf: Heat-Pump Cabin Heater

I wonder what efficiency they get?
I bet if the EPA actually made EVs do realistic test cycles instead of the antiquated 2 cycle test (which ICE vehicles haven’t used for a decade) every manufacturer would have heat pumps in their EVs.

 

[AlanSubie4Life]

I bet if the EPA actually made EVs do realistic test cycles instead of the antiquated 2 cycle test (which ICE vehicles haven’t used for a decade) every manufacturer would have heat pumps in their EVs.

I've been told in the 2019 and 2020 testing results, they are doing 5-cycle tests - the Excel worksheet showing all the inputs is at the very end of the large file. But they appear to be using the results to actually boost the range obtained from the 2-cycle test, in general (they're allowed to run the 5-cycle test and use that as data for the scalar). More recently, I've discovered these results ARE what they are using to justify the use of a larger scalar.

I haven't bothered to try to recreate the formulas. But they are public domain. Here are the formulas they use...somewhere here: 40 CFR § 600.114-12 - Vehicle-specific 5-cycle fuel economy and carbon-related exhaust emission calculations.

Here's an example. Something really really bad happened to the Model S Long Range in the 20 Degree Cold Test (only 67kWh available rather than 100kWh!) though since it didn't impact efficiency too much (at all?) it looks like it didn't hurt the range calc at all? It looks to me like only efficiency is taken into account, not capacity when cold. Anyway:

Search for 20 Degree here...Model S Long Range should have 100kWh:
https://iaspub.epa.gov/otaqpub/display_file.jsp?docid=49221&flag=1

At the end of this file they have the spreadsheet with the 5-cycle scalar calculation for the Model S Long Range. The formulas aren't shown, but see above. Again, have not tried to reconstruct but obviously would end up with the same answer they did:
https://iaspub.epa.gov/otaqpub/display_file.jsp?docid=48714&flag=1

Basically it seems to be a weighted result of the efficiencies obtained during the 5-cycle testing.

They'll do this for Model Y (that's where that 0.75 factor will come from) and actually they have already done for Model 3; see the end of this file:

https://iaspub.epa.gov/otaqpub/display_file.jsp?docid=48710&flag=1

 

[diamond.g]

And more to the topic at hand, I really don't see the electric motors making enough heat to provide any meaningful heat to the cabin with normal operation. It does a downright lousy job heating that 1,000 lb lump of metals and electrolytes underneath the floor, barely hitting 60 or 70° f after an hour drive around 25° F. The secret sauce to Model 3's industryleading efficiency is the motor...

All manufacturers pour large dollars into motor development to wring out as much as possible for each watt going into the motor. That leaves precious little heat waste.

Oh the motors could provide heat to the cabin, but overall efficiency would drop affecting how far you could go.

 

[I'm_Jp]

My 2017 Prius prime can reconfigure the AC to become a heat pump, to save a little on the battery.
In operation, it actually runs the AC on the outside air, cooling it, and brings the heat into the car.

However, it quits working at about 12F and below. There is not enough heat in the outside air to get.
The Prius manual also says it may quit working if the radiator ices up.

I've tried using an 120V electric space heater to pre-warm the car while parked in the garage on a timer
so that the inside would be toasty, but if you don't run the car heater while driving, the windows will fog.

Cold weather just sucks.

 

[realvvk]

At least the Leaf has a heat pump Heat-Pump Cabin Heater

Not the base model.

 

[MorrisonHiker]

I've tried using an 120V electric space heater to pre-warm the car while parked in the garage on a timer
so that the inside would be toasty, but if you don't run the car heater while driving, the windows will fog.

Cold weather just sucks.

If you live someplace dry like Colorado, Utah, Nevada, Arizona, etc., the low humidity makes it feel warmer and the windows don't fog up that often, at least not for me. I rarely have to defog the windows and get by with just the seat heaters unless there are several people in the car and we're talking a lot.

 

[camalaio]

I haven't read much of this thread, but my observations...

This is the worst insulated car I've driven. Shouldn't be a surprise given all the wonderful glass to look out of. For highway travel, this seems to be the main cause of reduced range w.r.t. heating. Simply throwing that precious heat out of the car at such a rate can't be helping.

There's multiple effects to consider here, but recently I was on the highway in -11°C (12°F) temps and thought I'd actually try the suggestion on only using the seat heaters since I was incredibly low on charge (forgot to plug in the previous night). My findings:

• Heck no. It gets cold immediately. 5 minutes later it's completely unbearably cold and I may as well stand outside. It feels like cold air is blowing at you as soon as the heat is off. This isn't just a comfort thing, I prefer to drive with hands and feet that aren't numb.
• When it's that cold, even on max, the seat heaters aren't putting out enough heat for your torso to feel warm. It's very welcome of course, but the steady state heat they apply after having them on for a while just isn't sufficient for this purpose.

I've done this in other cars (basically to reduce noise, another story) and can drive comfortably for quite a while in comparison. Certainly they don't feel like cold air starts blowing at me. However, I would slide the cover for the sunroof on the last car because it would make my head a bit cold.

When trying the same thing in town and driving slower, the impact of cold seepage was significantly reduced.

In consideration of the above, if a battery electric is our next car again, thermal insulation of the cabin will be something that I pay attention to. Hopefully Tesla also considers this, as it would be good for EVs overall. Could you imagine double-paned glass in your car?

 

[TomB985]

I haven't read much of this thread, but my observations...

This is the worst insulated car I've driven. Shouldn't be a surprise given all the wonderful glass to look out of. For highway travel, this seems to be the main cause of reduced range w.r.t. heating. Simply throwing that precious heat out of the car at such a rate can't be helping.

Just wanted to chime in and say I agree on all points. One of the first things I researched after buying this last year was a way to insulate the roof. Haven’t found a decent method yet, but better insulation would certainly be a big improvement in the cold.

 

[camalaio]

Just wanted to chime in and say I agree on all points. One of the first things I researched after buying this last year was a way to insulate the roof. Haven’t found a decent method yet, but better insulation would certainly be a big improvement in the cold.

I'm 90% certain there's a Bjorn Nyland video where he insulates the roof glass somehow. I think it was in the context of sleeping in the Model 3 overnight. At the time I didn't think it'd make a huge difference, now I can totally see it helping.

This video is not the one I'm thinking of, but seems related:

Or at least, I don't think that's the video. IIRC it involved the OEM mesh covers plus some cardboard or something? These: Model 3 Glass Roof Sunshade

That windshield still has a lot of surface area though.

EDIT: @TomB985, found it!

 

[DMLou]

Two words: biodielsel heater. Biodiesel should theoretically be carbon-neutral at least. I mean, you can make it from used cooking oil from your local fast food joint! So it's recycled too!

Kidding aside, I'll wait and see how good/bad it is when I get my car here in New England. I tend to keep my car heat turned down pretty low in the winter as I'm usually wearing a heavy coat, sweater, etc., when I'm in the car anyway.

Also, Technology Connections on YouTube had a good video on winter range, including with the heat on, in a Chevy Bolt. It might be of relevant interest as the Bolt would have similar issues to any Tesla:

 

[StellarRat]

As I pointed out earlier in this thread, Nissan has an available heat pump for the Leaf: Heat-Pump Cabin Heater

I wondered if any car used a heat pump. I guess I have my answer. I wasn't sure if a heat pump could be made small enough to use as a car heater. Now we know. Maybe Tesla will do something along those lines in the future. If you have heat pump for heating and AC that seems like a pretty efficient setup for a car.

 

[moridin2002]

...and the heat pump would be powered with....? I’m thinking the battery that makes you go!

What do you think your PTC heater is using in the car. Heat pumps are way more efficient than resistive heaters as long as it isn’t in extreme cold. Then, they just don’t work. Nothing wrong with a PTC heater to get things going and a heat pump to maintain temp other than additional cost. The heat pump that I had in my Kia Soul EV was far less costly in terms of energy use than what the PTC heater in my Model 3 costs.

 

[moridin2002]

I wondered if any car used a heat pump. I guess I have my answer. I wasn't sure if a heat pump could be made small enough to use as a car heater. Now we know. Maybe Tesla will do something along those lines in the future. If you have heat pump for heating and AC that seems like a pretty efficient setup for a car.

Kia Soul EV and VW e-Golf are a couple of other vehicles that have been using them (rather successfully) since 2015-2016. Likely that the Kona, Ioniq, and Niro EVs have one as well.

 

[TomB985]

I'm sure it all boils down to cost and complexity. Adding necessary components to convert the AC system to a heat pump would make the car more expensive and add more stuff that can break. The design processes have to keep that in mind. With estimated powertrain costs $10,000 over an equivalent ICE car, the rest of the car is produced at an extraordinary value.

I think the easier solution is better insulation. Throwing less energy out the windows and roof could make a huge impact, without adding much complexity.

 

[holmgang]

I haven't read much of this thread, but my observations...

This is the worst insulated car I've driven. Shouldn't be a surprise given all the wonderful glass to look out of. For highway travel, this seems to be the main cause of reduced range w.r.t. heating. Simply throwing that precious heat out of the car at such a rate can't be helping.

There's multiple effects to consider here, but recently I was on the highway in -11°C (12°F) temps and thought I'd actually try the suggestion on only using the seat heaters since I was incredibly low on charge (forgot to plug in the previous night). My findings:

• Heck no. It gets cold immediately. 5 minutes later it's completely unbearably cold and I may as well stand outside. It feels like cold air is blowing at you as soon as the heat is off. This isn't just a comfort thing, I prefer to drive with hands and feet that aren't numb.
• When it's that cold, even on max, the seat heaters aren't putting out enough heat for your torso to feel warm. It's very welcome of course, but the steady state heat they apply after having them on for a while just isn't sufficient for this purpose.

I've done this in other cars (basically to reduce noise, another story) and can drive comfortably for quite a while in comparison. Certainly they don't feel like cold air starts blowing at me. However, I would slide the cover for the sunroof on the last car because it would make my head a bit cold.

When trying the same thing in town and driving slower, the impact of cold seepage was significantly reduced.

In consideration of the above, if a battery electric is our next car again, thermal insulation of the cabin will be something that I pay attention to. Hopefully Tesla also considers this, as it would be good for EVs overall. Could you imagine double-paned glass in your car?

the problem with all this insulation is added weight to an already heavy car.

i havent experienced a problem with heat loss through the roof, but i do feel cold air enter the footwell when i turn off the heating (and my feet are generally insensitive!). havent figured out (or tried in earnest) how to control the vent vs recirc with the system off. everything seems to be dependent to having the actual hvac system ON, which is a bit annoying.