Car struggles to run AC for cabin and battery

[skshimer]

I hear what you are saying but why does the AC turn off when I drive the car in Sport Chrono mode, which needs a lot of cooling power to maintain the battery temperature? Is the fan not adequate in that mode?

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[PrudentOcean]

Sport+ will automatically reduce or turn off the A/C to maximize driving performance.

 

[skshimer]

You might want to look at this information about how the Taycan maintains battery temperature. I would imagine the Macan is similar.

https://www.orovel.net/insights/porsche-taycan-thermal-management

in addition, from the Taycan forum

“There is a single compressor (heat pump) for the interior and battery cooling and heating. Valves control what is used where. It is not necessary to activate the interior cooling to cool the battery if cooling is needed. That said, the optimal temperature for the battery is up there (though so are the temperatures out West). Unless your battery temp is above 120 deg. F, don't expect the car to engage cooling. You won't start to see thermal throttling until the battery temperature is even higher. I didn't get hot enough on a track day but I believe @daveo4EV has. I think my point in all of this is not to worry about it - don't second guess the car and simply enjoy the drive.”

 

[seabird]

You might want to look at this information about how the Taycan maintains battery temperature. I would imagine the Macan is similar.

Yes, that is exactly the case. The 3 coolant pumps and the radiator are, of course and as with all cars, the primary source of thermal control for the water-cooled components in the drivetrain. I'm not sure where you're seeing anything different.

The AC compressor is not doing the heavy lifting. As the post you quoted says, "Unless your battery temp is above 120 deg. F, don't expect the car to engage [AC] cooling."

 

[seabird]

I hear what you are saying but why does the AC turn off when I drive the car in Sport Chrono mode, which needs a lot of cooling power to maintain the battery temperature? Is the fan not adequate in that mode?

For the same reason that AC is turned off for ICE cars in track mode. Running the cabin climate system uses power and generates heat, both of which take away from the highest possible performance.

 

[skshimer]

I don’t understand what you are saying. The mechanics of how cold/warm air for the cabin or the temperature of the liquid supplied to control the battery temperature is immaterial. All the BTU’s needed to hear or cool the battery and the cabin are provided by the heat pump. Not fans blowing across a radiator as you stated in a previous post. Just an FYI. I pay twice as much to hear my house than to cool my house because the temperature differential inside/outside is twice as much in the winter than the summer. Air at -15F is very warm compared to absolute Zero K.

 

[daveo4EV]

You might want to look at this information about how the Taycan maintains battery temperature. I would imagine the Macan is similar.

https://www.orovel.net/insights/porsche-taycan-thermal-management

in addition, from the Taycan forum

“There is a single compressor (heat pump) for the interior and battery cooling and heating. Valves control what is used where. It is not necessary to activate the interior cooling to cool the battery if cooling is needed. That said, the optimal temperature for the battery is up there (though so are the temperatures out West). Unless your battery temp is above 120 deg. F, don't expect the car to engage cooling. You won't start to see thermal throttling until the battery temperature is even higher. I didn't get hot enough on a track day but I believe @daveo4EV has. I think my expoint in all of this is not to worry about it - don't second guess the car and simply enjoy the drive.”

my 2020 Taycan would limit throttle power at 132f battery temp but only on track - even then it was still responsive but lacked top end power - battery temp would recover quickly if you stopped using max power continuously

the battery actually got cooler during fast charging vs the max temp of 132f when tracking the turbo

 

[skshimer]

I don’t understand what you are saying. The mechanics of how cold/warm air for the cabin or the temperature of the liquid supplied to control the battery temperature is immaterial. All the BTU’s needed are provided by the heat pump. Not fans blowing across a radiator as you stated in a previous post. It is not an AC compressor. As in all heat pumps it can move BTU’s equally efficiently in both directions. Do you know the difference between an AC and a heat pump?

 

[seabird]

All the BTU’s needed are provided by the heat pump.

I’m not sure where you got this idea, but it is 100% false.

Just like any other water-cooled car, the primary source of cooling is the thermal mass in the coolant, radiator, and air moving through because of the giant fan in the front.

Not fans blowing across a radiator as you stated in a previous post.

Crazy take. That is precisely why there is a radiator and fan and a water cooling loop. The little AC evaporator does not need a huge secondary radiator and fan.

The only reason gas cars don’t use a heat pump setup in their AC system is because the waste heat from the engine is free, so there is no need to scavenge the ambient air.

It is not an AC compressor.

Even crazier take. It is ABSOLUTELY an AC compressor. A heat pump is just a reversible AC system.

As in all heat pumps it can move BTU’s equally efficiently in both directions.

The heat pump is not the issue. The source of the heat energy is the issue. And no, they are not equally efficient in both directions because there is not an equal number of BTUs to move in both directions. There is always a temperature gradient.

Do you know the difference between an AC and a heat pump?

I don’t think you’re the one who should be asking that question.

 

[skshimer]

You are arguing about heat pumps with a Ph.D. in Physical Chemistry. Ciao.

 

[fubar.droid]

You might want to look at this information about how the Taycan maintains battery temperature. I would imagine the Macan is similar.

https://www.orovel.net/insights/porsche-taycan-thermal-management

in addition, from the Taycan forum

“There is a single compressor (heat pump) for the interior and battery cooling and heating. Valves control what is used where. It is not necessary to activate the interior cooling to cool the battery if cooling is needed. That said, the optimal temperature for the battery is up there (though so are the temperatures out West). Unless your battery temp is above 120 deg. F, don't expect the car to engage cooling. You won't start to see thermal throttling until the battery temperature is even higher. I didn't get hot enough on a track day but I believe @daveo4EV has. I think my point in all of this is not to worry about it - don't second guess the car and simply enjoy the drive.”

This is not what I noticed. My battery temperature was 101 F when I noticed my cabin AC was lukewarm and not keeping up with the outside temperature (109 F). By the time the cabin AC became cold again, the battery temp was around 95 F, so the car definitely routed the AC to the battery much sooner than 120.

It's a bit disappointing that it wasn't designed to be able to handle both properly being that my ICE can handle this heat and keep the AC running just fine.

 

[seabird]

You are arguing about heat pumps with a Ph.D. in Physical Chemistry. Ciao.

I'm not sure where you think there's an argument about heat pumps. You are arguing with the basic facts that can be verified from a parts diagram or a simple look inside your car.

Not all EVs have water/HVAC heat exchangers to supplement the cooling system. Not all EVs even have heat pumps to begin with. But essentially all EVs other than the old Leaf have a normal water cooling system just like every water-cooled car on earth.

You don't need a PhD in chemistry to understand that a 400W fan and water pump providing 30-50K BTUs of cooling is a much more effective setup than the 5000W HVAC system providing 15K BTUs that needs to be split between the cabin and the water loop. And you need a lot more than a PhD in chemistry to tell an actual engineer that cooling for a car's drivetrain is coming from the AC compressor and not the car's primary cooling system.

 

[seabird]

It's a bit disappointing that it wasn't designed to be able to handle both properly being that my ICE can handle this heat and keep the AC running just fine.

It's just the nature of the beast, like ICE cars not having any heat until the engine warms up.

There's no designing around the fact that putting hot water through the AC system reduces the ability to cool air, as it's already designed to open that valve only when the radiator can't cool down the battery on its own.

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