Why does Tesla use a Resistance Heater instead of Heat Pump

[hiroshiy]

My two cents: I bet that they did not use a HP because as every automakers, Tesla relies on OEMs for many, many parts including AC. And as on ICEs a heating source is not required, AC heat pumps are cooling only. Tesla had to use these HP. as it was probably much more expensive to make an OEM develop a dedicated reversible one. This may change in the future with growth of EV market. A reversible heat pump would for sure lower a lot energy drain when heating the car in cool (but not freezing) climates.
Small series are costly for an OEM part, and 200k/year is a small serie in the automotive industry. Remember, even for the Model S wheel selectors, Tesla had to reuse the ones from Mercedes.

Now when it comes to heating the battery pack. A heat pump is more efficient than a battery pack. The efficiency is lower on cold temperatures, but will generally still stay better than a resistor. BUT, the heating power will be also very low. For instance, a 3kW resistor will produce 3kW of heat whatever the conditions. A 1kW heat pump may generate 4kW of heat at 20°C, 2.5kW at 0°C and 1.5kW at -20°C (numbers are illustrative only). Wich means, that at -20°C, it's still slightly more efficient than a resistor, but the heating power is very low. And thus, initiating a battery charge will be super long.

The best world would involve both a reversible heat pump and a resistor. The resistor costs virtually nothing, but it adds some complexity to the wiring and design.

So the reasons why they do not have a reversible heat pump are:
1) This is not a standard OEM part as the ICE cars doesn't have one.
2) A resistor is still required, which adds to the overall complexity.

Cheers!

I think there are a few major tier-1 automotive suppliers who developed EV heat pumps.
EV向け空調システム用ヒートポンプシステムの最新動向 - 自動車業界調査レポート【オートモーティブ・ジョブズ(AJ)】
(Japanese article, please use Google translate to read in English)
Toyota is using one that works @minus 10C in 2017 Prius PHV (two years ago). Also I can see names like Hanon, which I believe Tesla is also purchasing current A/C from.

 

[David99]

The Leaf and VW eGolf have heat pumps. Both are low priced (relatively speaking) and pure EVs.
AFAIK the Model 3 also comes without a heat pump. We can only speculate why. There are a few things Tesla doesn't do that would make sense at first, but I also don't think Tesla makes every decision better than everyone else.

 

[MP3Mike]

I think a big portion of the reason is that the AC is used to cool the batteries, motor, inverter, power electronics, AP computer, etc. So even while you might want to heat the cabin the car is running the AC to provide necessary cooling.

So you would either have to have a separate cabin/car systems, or you have to have a complicated system that can both heat and cool at the same time. (I don't know if that is reasonably possible.)

The Leaf and VW eGolf have heat pumps. Both are low priced (relatively speaking) and pure EVs.

Do either of them use the AC system to cool the car equipment?

 

[AWDtsla]

The Leaf and VW eGolf have heat pumps. Both are low priced (relatively speaking) and pure EVs.
AFAIK the Model 3 also comes without a heat pump. We can only speculate why. There are a few things Tesla doesn't do that would make sense at first, but I also don't think Tesla makes every decision better than everyone else.

I feel like I might be repeating myself in this years long thread - but the man himself JB Straubel said that heat pumps were a good solution to winter efficiency here. If you look hard enough, you can find the video.

 

[AWDtsla]

I think a big portion of the reason is that the AC is used to cool the batteries, motor, inverter, power electronics, AP computer, etc. So even while you might want to heat the cabin the car is running the AC to provide necessary cooling.

So you would either have to have a separate cabin/car systems, or you have to have a complicated system that can both heat and cool at the same time. (I don't know if that is reasonably possible.)



Do either of them use the AC system to cool the car equipment?

You don't understand the system. The AC does not provide additional cooling to the main coolant loop when the outdoor temperature is low. This would not be smart, to put it bluntly. The heat exchanger between the coolant loop and the AC loop is already valved.

 

[David99]

I think a big portion of the reason is that the AC is used to cool the batteries, motor, inverter, power electronics, AP computer, etc. So even while you might want to heat the cabin the car is running the AC to provide necessary cooling.

So you would either have to have a separate cabin/car systems, or you have to have a complicated system that can both heat and cool at the same time. (I don't know if that is reasonably possible.)



Do either of them use the AC system to cool the car equipment?

When it's cold outside the AC definitely doesn't run to cool any components. Short of supercharging of course.

But if you need heating and cooling at the same time a heat pump does exactly that. One side gets cold the other side warm. And it does so at incredibly high efficiency.

 

[MP3Mike]

You don't understand the system. The AC does not provide additional cooling to the main coolant loop when the outdoor temperature is low. This would not be smart, to put it bluntly. The heat exchanger between the coolant loop and the AC loop is already valved.

So the car never runs the AC system to cool the anything when it is 65 degrees out, but the person in the cabin wants it heated to 75? Not even while accelerating under heavy load or shortly after Supercharging?

 

[MP3Mike]

But if you need heating and cooling at the same time a heat pump does exactly that. One side gets cold the other side warm. And it does so at incredibly high efficiency.

OK, so what about when you need to cool the APE and motor, the passenger has their AC set to 70 and the driver has their heat set to 80?

You've got a lot of switching and complexity involved in that. And my guess is Tesla decided that it wasn't worth it.

 

[AWDtsla]

So the car never runs the AC system to cool the anything when it is 65 degrees out, but the person in the cabin wants it heated to 75? Not even while accelerating under heavy load or shortly after Supercharging?

Did you see what happens to Tesla's in a really hot environment with a hot pack? You get a message saying cooling performance is reduced.

These arguments are tired.

 

[David99]

OK, so what about when you need to cool the APE and motor, the passenger has their AC set to 70 and the driver has their heat set to 80?

You've got a lot of switching and complexity involved in that. And my guess is Tesla decided that it wasn't worth it.

Looking at the Model S and Model 3, Tesla has tackled some seriously complex tasks and came up with very smart solutions. A heat pump isn't hard to implement as we have seen in other EVs. But obviously Tesla didn't think it was worth it. Or their data shows that most miles driven in their fleet would not benefit much. Or maybe Elon is just a sweaty type and never needs the heat on LOL

Again, we can only speculate. Not every decision made at Tesla is the result of extensive research and thinking. Sometimes it is just as simple as a project manager making a decision and then defending his decision forever to not look bad for making a wrong call. Happens all the time at every company.

 

[AWDtsla]

Looking at the Model S and Model 3, Tesla has tackled some seriously complex tasks and came up with very smart solutions. A heat pump isn't hard to implement as we have seen in other EVs. But obviously Tesla didn't think it was worth it. Or their data shows that most miles driven in their fleet would not benefit much. Or maybe Elon is just a sweaty type and never needs the heat on LOL

Again, we can only speculate. Not every decision made at Tesla is the result of extensive research and thinking. Sometimes it is just as simple as a project manager making a decision and then defending his decision forever to not look bad for making a wrong call. Happens all the time at every company.

They know people in colder climates opt for larger batteries, so it would be like anti-selling. However the more obvious answer is probably right. Just like schmutz covering the headlights and all camera's except under the windshield in about 15 minutes of winter driving, I just don't think they "get it" with all their engineers being in California. Just think it took them 7 YEARS after Model S was introduced to add battery heating for supercharging. 6 years for remote control of seat and steering wheel heaters. 5 years to remember your heated steering wheel setting.

 

[AWDtsla]

Teslabjorn compares an EV with a heatpump vs Model 3, wonders why Model 3 doesn't have one. Consumes 3x as much energy even though the Model 3 is kept indoors. My guess would be 4x if it was kept outdoors.

 

[David99]

I wish die hard Tesla fans would just stop defending Tesla no matter what. 20 pages of arguing how a heat pump isn't working in an EV, too expensive, ...

 

[mongo]

I wish die hard Tesla fans would just stop defending Tesla no matter what. 20 pages of arguing how a heat pump isn't working in an EV, too expensive, ...

If you are refering to @AWDtsla's post, you might want to consider the fact that the 2019 e-Soul has an AIR COOLED battery pack.

2020 Kia Soul EV first drive review: 243 electric miles in the box
The 2020 version is liquid cooled, can only charge at 100kW, and takes 45 minutes to go from 20-80% (64kWh pack).

 

[David99]

If you are refering to @AWDtsla's post, you might want to consider the fact that the 2019 e-Soul has an AIR COOLED battery pack.

The topic of this discussion is about using a heat pump for cabin warming.

 

[mongo]

The topic of this discussion is about using a heat pump for cabin warming.

If you ignore that Tesla needs to use the AC for pack cooling then the discussion is pointless.

Leaf: air cooled pack, heat pump
e-Soul: air cooled pack, heat pump
Tesla: thermally regulated pack (active heating and cooling), no heat pump

 

[AWDtsla]

If you ignore that Tesla needs to use the AC for pack cooling then the discussion is pointless.

Leaf: air cooled pack, heat pump
e-Soul: air cooled pack, heat pump
Tesla: thermally regulated pack (active heating and cooling), no heat pump

I-Pace has a liquid cooled pack AND heat pump for cabin heating. The heat pump can even scavange otherwise unusable heat from car electronics to bring the cabin up to temp.

This grasping at straws is ridiculous. Why do you guys keep doing it? Pro-Tesla trolling.

 

[mongo]

I-Pace has a liquid cooled pack AND heat pump for cabin heating. The heat pump can even scavange otherwise unusable heat from car electronics to bring the cabin up to temp.

This grasping at straws is ridiculous. Why do you guys keep doing it? Pro-Tesla trolling.

It is hardly trolling to point out out glaring differences between vehicles that that being used as examples of why Tesla should be doing something. Why do you insist on using personal labeling instead of sticking to the facts? The I-Pace with a two stage liquid cooled battery pack is a good point of comparison. The e-Soul with only air cooling is not.

 

[AWDtsla]

It is hardly trolling to point out out glaring differences between vehicles that that being used as examples of why Tesla should be doing something. Why do you insist on using personal labeling instead of sticking to the facts? The I-Pace with a two stage liquid cooled battery pack is a good point of comparison. The e-Soul with only air cooling is not.

Why does Tesla use a Resistance Heater instead of Heat Pump

 

[taraquin]

I wish Tesla would implement HP in their models soon. After drivingca lit of Nissan Leaf with and without HP I saw a big difference in consumption, especially when temps are between 10C and - 5C. I have also driven a lot with Kia Soul and Kona with HP and in that temp-range thete is extremely little extra consumption. Typically a 0C the leaf and Kia with HP uses 0.5-1kW to heat the cabin after driving for 5minutes with 20C cabintemp. My Model S and the 3s I have driven uses 2-3kW all the time at same temp/settings. A HP is a really cheap way to increase range significantly in many parts of the world most of the year.