Heating the MINI Cooper SE's Cabin

[insightman]

@Puppethead noted in the Tires (Summer/Winter/All-Season) thread that the MINI Cooper SE's heat pump helps reduce the battery's burden of warming the cabin:

There's also the heat pump, which, if I understand its function correctly, should help quite a bit since it lets motor/battery waste heat be used for cabin warming instead of relying solely on a resistance heater. It must make a big difference since Tesla's added a heat pump to their Model Y.

It's interesting to see how much plumbing is required under the SE's hood to provide cooling for the battery, cooling for the motor, cooling for the electronics, and heating for the cabin. It makes the plumbing for an internal-combustion engine look simple in comparison.

The heat pump is such a good idea that it gets all the press, but what about the resistance heater? I assume the resistance heater is what warms the cabin when the car is plugged in, because the motor, inverter, and a fully-charged battery are not creating any heat for the heat pump to transfer to the cabin.

The whole reason for a heat pump is to provide a means of heating the cabin that requires less battery power than the resistance heater. So I want to know what I can do to maximize the usage of the heat pump and minimize the activity of the resistance heater.

Here are my questions about the heat pump and the resistance heater:

1. How much does heat pump activity reduce the MINI Cooper SE's range?
   
2. How much does resistance heater activity reduce the MINI Cooper SE's range?
   
3. At what temperature does the resistance heater kick in to assist the heat pump?
4. Do I need to install an LED indicator to know when the resistance heater kicks in?
   
5. Will setting the climate-control temperature to 60 degrees favor heat pump usage?
6. Is selecting Green+ mode the only way to disable the resistance heater?
7. How does Green mode restrict heat pump and the resistance heater operation?
8. Does the BMW i3's heat pump work the same way as the MINI Cooper SE's?

I'm sure others have even better questions and, hopefully, ideas about extending range when the weather turns cold.

 

[Puppethead]

From that article on the Model Y:

Tesla recommends that if you can get away with it, using the seat heaters is more efficient than using the cabin heater.​

Based on that one can infer that the resistance heater tends to use a lot of electricity. I've also heard Tesla owners say running the AC does not drain the battery much at all.

I have geothermal heating/cooling in my house which uses heat pumps, and I can say from experience it is an extremely efficient way to manage temperature both in the summer and the winter.

I also found this BMW i3 preconditioning article, which has some interesting information (including in the comments). Since the article is four years old I'd think the SE would be more refined.

The Motorer's Guide says Green Mode reduces acceleration only. I've been changing my cabin temperature to try and regulate how much the heating and cooling come on, but it's all guesswork based on what's coming out of the air vents since there's no indicator anywhere as to when the systems are on.

 

[GvilleGuy]

All I had seen so far was the top view of the engine with the cage reinforcement. That is much more complex than I expected.

 

[insightman]

All I had seen so far was the top view of the engine with the cage reinforcement. That is much more complex than I expected.

When I first found and posted that photo, an anti-MINI troll claimed that big problems were ahead because BMW hoses are known to be short-lived. My Google search didn't discover any articles about such problems. I assume the coolant temperatures in our electric MINI Coopers are lower than in ICE MINI Coopers, so our hoses should experience less thermal stress. Now I have another question: How hot does the coolant get in the various coolant loops within the MINI Cooper SE? I hope I can someday see a schematic diagram of the cooling system.

 

[Puppethead]

Here's a short overview of how heat pumps work for both heating and cooling.

 

[SmartElectric]

From that article on the Model Y:

Tesla recommends that if you can get away with it, using the seat heaters is more efficient than using the cabin heater.​

Based on that one can infer that the resistance heater tends to use a lot of electricity. I've also heard Tesla owners say running the AC does not drain the battery much at all.

There are 3 very different systems used across Tesla vehicles.

Our 2013 Model S (like all Model S up to current day) uses two different resistive heating systems, one for cabin, one for battery pack, I should know, I've had the pack heater core replaced a few years ago, and the cabin heater core a few years before that. Perfect since. Of course, resistive heating uses nearly 6kW peak to get the heater core up to temperature, and then a few hundred watts sustained. If the pack is cold (-10C is cold), that's another thing entirely, could take an hour to heat that pack at 6kW, so yeah 6 kWh, which is a fraction of the 75 kWh total capacity.

Whereas Model 3 (up to 2020) uses the rear motor to heat the cabin and pack, Tesla "stalls" the motor to cause heat in the windings, which is then gathered via coolant loop and fed through the pack and cabin heating systems. This uses up to 5kW I believe (don't own a Model 3), and due to a much smaller pack and cabin, uses a lot less kWh for same heating vs Model S.

Model Y has the heat pump integrated, so uses far less electricity for heating pack or cabin. On the order of 3x less electricity for the same heat on a cold day.

^ so it depends on which Tesla owner you ask

 

[Godfrey]

I picked up our new Cooper SE on Sunday and have mostly driven it when it's hot outside. Turning on AC has a pretty big impact on the estimated range shown on the dash (accurate or not), so I've tried manually cycling the AC on and off with the temp set at 60 to minimize the amount of time the AC is being used. Compared to ICE cars I've owned, this seems to be pretty effective in keeping the cabin comfortable; even after the AC is off, cool air continues to blow through the vents for a while. I assume refrigerant continues to cool the air after AC is turned off as the refrigerant gradually gets less cool. It's a pain to keep turning AC on and off, though.

I'm wondering what's going on behind the scenes if I have AC running on a hot day with the temperature set to, say, 74 degrees. In ICE cars, I'm under the impression that air is cooled by refrigerant and heated by engine coolant at the same time. Does anybody know what the Cooper SE does to maintain the temperature?

I don't know much about HVAC, but here are the possibilities that occur to me:

• A) AC is being cycled on and off.
• B) AC has ability to be scaled back some other way (other than cycling).
• C) AC cools air and resistance heat warms air at same time.
• D) I've been assuming that the heat pump is used for both AC and heating, but maybe there's a separate AC unit and both that and heat pump are running at same time to both cool and heat.
• E) Most likely, something I haven't thought of.

Anyway, it would be nice to know how efficient setting climate control to a comfortable temperature is compared to leaving at 60 and turning AC on and off, on and off, etc.

 

[Puppethead]

I set the temperature to between 72-74 ºF (depending if it's above 90 ºF outside or not), and leave the cooling set to "auto". That seems to work pretty well and doesn't impact my range much. If I want to "turn off" the A/C I'll adjust the temperature up a few degrees.

 

[Carsten Haase]

I picked up our new Cooper SE on Sunday and have mostly driven it when it's hot outside. Turning on AC has a pretty big impact on the estimated range shown on the dash (accurate or not), so I've tried manually cycling the AC on and off with the temp set at 60 to minimize the amount of time the AC is being used. Compared to ICE cars I've owned, this seems to be pretty effective in keeping the cabin comfortable; even after the AC is off, cool air continues to blow through the vents for a while. I assume refrigerant continues to cool the air after AC is turned off as the refrigerant gradually gets less cool. It's a pain to keep turning AC on and off, though.

I'm wondering what's going on behind the scenes if I have AC running on a hot day with the temperature set to, say, 74 degrees. In ICE cars, I'm under the impression that air is cooled by refrigerant and heated by engine coolant at the same time. Does anybody know what the Cooper SE does to maintain the temperature?

I don't know much about HVAC, but here are the possibilities that occur to me:

• A) AC is being cycled on and off.
• B) AC has ability to be scaled back some other way (other than cycling).
• C) AC cools air and resistance heat warms air at same time.
• D) I've been assuming that the heat pump is used for both AC and heating, but maybe there's a separate AC unit and both that and heat pump are running at same time to both cool and heat.
• E) Most likely, something I haven't thought of.

Anyway, it would be nice to know how efficient setting climate control to a comfortable temperature is compared to leaving at 60 and turning AC on and off, on and off, etc.

The AC in ICE cars typically cycles on and off to maintain a target refrigerant temperature because the compressor is belt driven and can only go the same speed as the engine rpm.

Because the AC compressor in EVs is now typically powered by it's own electric motor, they can be made more efficient by making them variable speed.

I found the attached pdf about the BMW i3 HVAC system that discusses the AC compressor that says it is a variable speed unit ("EKK" starting on the bottom of page 28). The MINI shares a lot with the i3 so it's likely the same compressor (I have noticed that the AC is reduced when stationary, like is noted on page 30).

In all likelihood, you are probably using more energy by manually cycling the AC yourself. The temperature differential between inside/outside is what ultimately determines the required energy to maintain interior temperature so if you want to use less energy the best bet is to set the AC (or heat) to as close to outside as is comfortable.

Oh and the HVAC unit has motorized flaps to divert air around the heater unit so you are not reheating the cooled air. (Although you can set the AC on with heat on to reduce the humidity of the cabin which is useful for defrosting)

 

[Godfrey]

The AC in ICE cars typically cycles on and off to maintain a target refrigerant temperature because the compressor is belt driven and can only go the same speed as the engine rpm.

Because the AC compressor in EVs is now typically powered by it's own electric motor, they can be made more efficient by making them variable speed.

I found the attached pdf about the BMW i3 HVAC system that discusses the AC compressor that says it is a variable speed unit ("EKK" starting on the bottom of page 28). The MINI shares a lot with the i3 so it's likely the same compressor (I have noticed that the AC is reduced when stationary, like is noted on page 30).

In all likelihood, you are probably using more energy by manually cycling the AC yourself. The temperature differential between inside/outside is what ultimately determines the required energy to maintain interior temperature so if you want to use less energy the best bet is to set the AC (or heat) to as close to outside as is comfortable.

Oh and the HVAC unit has motorized flaps to divert air around the heater unit so you are not reheating the cooled air. (Although you can set the AC on with heat on to reduce the humidity of the cabin which is useful for defrosting)

After reading your reply and perusing the document (thanks for the link), it's clear that I need to stop trying to outsmart the car. I never really adjusted my thinking about using heating and cooling in cars even after they started having automatic climate control. Still thinking in terms of the manual controls from the past.

This is great information. Thanks to the other commenters as well. I'm glad I asked.

 

[Newkirk]

3. At what temperature does the resistance heater kick in to assist the heat pump?

I don't know, but in the mild north Florida winters, we use heat pumps for both AC and heat. The heat pump usually works fine down to about 32F, and at some point (maybe around 30F?) the resistance heater (AUX heat) kicks in because the heat pump can't keep up. It'll also kick in if you try and raise the temperature too much at once (say, going from 67F to 70F). It doesn't usually get that cold here, so the resistance heater doesn't come on much, but I also keep it cool at night, around 67F. I also have an electric heat pump water heater, which has a heat-pump-only mode, as well as the conventional resistance heater. I suspect my garage doesn't get any cooler than around 40F, but it's always worked just fine on heat pump mode. Those water heaters are supposed to work in heat pump mode down to 35F, so at that point the resistance heater might kick in. It would be cool if there were a heat-pump-only mode on the SE.

 

[Whosehouse]

Anyway, it would be nice to know how efficient setting climate control to a comfortable temperature is compared to leaving at 60 and turning AC on and off, on and off, etc.

I’ve had my mini for a few months and have driven it over 4k miles in the South. I have never turned the A/C off (I’m usually around 68-69 degrees, auto, one or two bars unless my wife is with me and then it’s like four bars). The temps are usually high 80s to low 90s. Not once has it ever significantly impacted my battery. Even with highway driving, I’m always well over epa estimate.

I would set the a/c to whatever is comfortable for you and enjoy your drive. I’m curious to see how heating goes in the winter but my guess is our temps won’t ever get crazy enough to be really bad.

 

[GvilleGuy]

I’ve had my mini for a few months and have driven it over 4k miles in the South. I have never turned the A/C off (I’m usually around 68-69 degrees, auto, one or two bars unless my wife is with me and then it’s like four bars). The temps are usually high 80s to low 90s. Not once has it ever significantly impacted my battery. Even with highway driving, I’m always well over epa estimate.

I would set the a/c to whatever is comfortable for you and enjoy your drive. I’m curious to see how heating goes in the winter but my guess is our temps won’t ever get crazy enough to be really bad.

I'm with you. Summer driving in South Carolina here. Never turn the A/C off! And I still get good results on my calculated ranges when I'm taking longer trips in Green mode.

 

[GetOffYourGas]

I would set the a/c to whatever is comfortable for you and enjoy your drive. I’m curious to see how heating goes in the winter but my guess is our temps won’t ever get crazy enough to be really bad.

I picked up my Mini in January in upstate NY, so I got a few months of cold (sometimes as low as teens, below that I didn't drive the Mini due to the summer tires). The heat pump is truly outstanding. I saw a loss of maybe 20% when turning on the heat, even at those temps. Range was as low as mid-80s, but typically in the 90s (miles). This is in stark contrast to my Bolt with a resistance heater. The Bolt sees a drop in range of up to 40% with temps in the teens!

When temperatures were much more moderate (say at or above freezing), the range hit was less than 10%. It's easy to get 100 miles out of this car with the heat on when it is 32F outside.

 

[Puppethead]

I set the temperature to between 72-74 ºF (depending if it's above 90 ºF outside or not), and leave the cooling set to "auto". That seems to work pretty well and doesn't impact my range much. If I want to "turn off" the A/C I'll adjust the temperature up a few degrees.

Today I was driving in 25 ºF temperature, and on a whim I decided to turn off the A/C and wow, the GOM immediately showed an extra 5 miles range. The GOM is notoriously inaccurate, but maybe the A/C draws more than expected when on in cold temperatures.