Car struggles to run AC for cabin and battery

[fubar.droid]

It was 109 F where I was yesterday and noticed for the first time that the AC can't seem to keep both the cabin and battery cool. I have the AC set to "Low". The battery temp was 101 when I got back to the car and drove home and noticed the AC wasn't working very well. It was struggling to keep the cabin cool, it was just barely acceptable as far as cooling goes but if my entire car wasn't nano ceramic tinted, I'd imagine it would have been hot inside. Anyway I wasn't sure why the AC wasn't working but then noticed the battery temp was dropping, was around 94 F and that's when I thought maybe it can't cool both well. At some point in the drive the cabin AC became cold again so I'm guessing the cooling system for the battery stopped running? This was after a good 10 minute drive so I'm not talking about at the start of the drive.

I don't know, just something I observed and I recall someone else mentioning on this board that their AC was struggling too.

Does the same AC system run both the battery and cabin cooling?

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[LinuxLars]

It was 109 F where I was yesterday and noticed for the first time that the AC can't seem to keep both the cabin and battery cool. I have the AC set to "Low". The battery temp was 101 when I got back to the car and drove home and noticed the AC wasn't working very well. It was struggling to keep the cabin cool, it was just barely acceptable as far as cooling goes but if my entire car wasn't nano ceramic tinted, I'd imagine it would have been hot inside. Anyway I wasn't sure why the AC wasn't working but then noticed the battery temp was dropping, was around 94 F and that's when I thought maybe it can't cool both well. At some point in the drive the cabin AC became cold again so I'm guessing the cooling system for the battery stopped running? This was after a good 10 minute drive so I'm not talking about at the start of the drive.

I don't know, just something I observed and I recall someone else mentioning on this board that their AC was struggling too.

Does the same AC system run both the battery and cabin cooling?

I'm pretty sure the battery uses air cooling (someone correct me if I'm wrong). Every time I've driving over a patch of fine powder(dirt, dust, etc) when it's hot, a cloud of said powder comes up from under the car driven by the cooling fans.

I ordered mine with double glass and ventilated front seats. And yeah, on really hot days 102+, it's OK. I find using the seat ventilation, I can set the temp to 78, and it's comfortable, and doesn't drain the battery.

 

[rjf]

Using the ventilated seats really helps keep the interior cool in the high temperatures and very high humidity we experience in the south eastern portion of the US.

 

[dbsb3233]

We've noticed that the AC in ours doesn't cool the car down nearly as fast as our Mach-E does. It's not *bad* per se (it's probably more average), but I expected better. I've always been impressed with how good the AC in our Mach-E is.

I don't like the AC blowing directly on me, so I have the vents aimed to either side, to cool the cabin down. It can take a good 5-10 minutes to cool the Macan down to where it doesn't feel warm. And remote starting it early only helps *some*. In the Mach-E it only needs maybe 3 minutes to go from 95F to 72F.

But the ventilated seats in the Macan do help mitigate that some.

 

[PrudentOcean]

Do you have the ventilation set to Soft? That reduces the cooling.

 

[skshimer]

Something that may be related to this issue. When I put the car into chrono mode and it is hot outside, it turns off the AC, I believe in anticipation of heavy duty battery usage requiring heating or cooling.

The whole cooling and heating runs of heat pumps. The fans pulling air across the coils causes dust clouds around the car on unpaved lots. I normally do not have the battery conditioning engaged. When I pulled into a dirt parking lot the other day I turned off the AC in this car and had no problems with dust.

 

[craz8]

I'm pretty sure the battery uses air cooling

Nope. I don't think any modern EV uses air cooling of the battery pack. The Nissan Leaf is the one everyone knows about though, and it has all sorts of problems in high temperatures

As everyone has noticed, the battery and cabin cooling systems are not independent of each other, which can help reduce energy usage at some times, but at the extremes, is often less successful at keeping you comfortable.

 

[dbsb3233]

That would probably explain why it's not as strong as some other cars. Heat pumps are great for efficiency, but typically aren't as strong.

 

[dbsb3233]

Do you have the ventilation set to Soft? That reduces the cooling.

Ours are both set to strong.

 

[PrudentOcean]

Something that may be related to this issue. When I put the car into chrono mode and it is hot outside, it turns off the AC, I believe in anticipation of heavy duty battery usage requiring heating or cooling.

Chrono Mode is part of the Sports Chrono package which also gets you Sport+, and in Sport+ the car will automatically disable AC when using Launch Control. It may even engage ECO code for the sound system, I haven't tested that yet.

 

[prime]

It was 109 F where I was yesterday and noticed for the first time that the AC can't seem to keep both the cabin and battery cool. I have the AC set to "Low". The battery temp was 101 when I got back to the car and drove home and noticed the AC wasn't working very well. It was struggling to keep the cabin cool, it was just barely acceptable as far as cooling goes but if my entire car wasn't nano ceramic tinted, I'd imagine it would have been hot inside. Anyway I wasn't sure why the AC wasn't working but then noticed the battery temp was dropping, was around 94 F and that's when I thought maybe it can't cool both well. At some point in the drive the cabin AC became cold again so I'm guessing the cooling system for the battery stopped running? This was after a good 10 minute drive so I'm not talking about at the start of the drive.

I don't know, just something I observed and I recall someone else mentioning on this board that their AC was struggling too.

Does the same AC system run both the battery and cabin cooling?

You likely have the AC issue that a few of us here have had. I would have Porsche check this out. My coolant was low and they also found a leak.

 

[USMA81]

I live in AZ and have been pleased with the AC cooling. I did spec the back passenger window screens and the optional thermal glass. I also drive the car most often from home where it is garaged and so isn’t heat-soaked when I get in. I use window shades 100% of the time when parking outside.

 

[seabird]

The whole cooling and heating runs of heat pumps.

There is a heat pump and an exchange manifold, but the car's primary cooling of both the battery and the cabin do not rely on heat pumps (the only time the heat pump takes the lead on anything is generating cabin heat in winter).

The primary means of cabin cooling is a standard automotive AC compressor, charged with R1234yf refrigerant oil.

The primary means of battery cooling is a ~6qt water loop, connected to radiators and fans in the front of the car.

These systems are connected through the AC evaporator, which can be used to cool down the water temp slightly in very hot conditions when the ambient air isn't providing enough cooling for the battery on its own. This massively reduces cabin cooling power but only slightly lowers battery temperatures. It is still primarily the flow of air across the radiator that is moving excess heat out of the battery.

The heat pump is designed primarily to extract heat from the air so that you don't need to run the PTC heater as much in winter. It doesn't do a whole lot to dump heat into the air, which is what the water loop and radiators are for.

Nope. I don't think any modern EV uses air cooling of the battery pack.

Right. They are water-cooled by the exchange of heat through the radiators. But what he probably meant in context is that it's airflow, rather than a refrigerant, that cools the battery.

 

[skshimer]

I hear what you are saying but heat pumps work in both cooling mode and heating mode. In one direction they extract heat from the ”outside” air and in the other they extract heat from the ”inside” air. All the same compressor. The whole SE US uses heats pumps to heat AND cool their homes. In newer Tesla MS’s the heat pump cools and heats the cabin and the battery for optimal charging. Why would Porsche not use the heat pumps to provide both cooling and heating capacity for everything in the car? Heat pumps still use fans and radiators.

 

[seabird]

I hear what you are saying but heat pumps work in both cooling mode and heating mode. In one direction they extract heat from the ”outside” air and in the other they extract heat from the ”inside” air. All the same compressor.

Heat pumps move heat but are not equally effective at both cooling and heating, especially when the two air sources are radically different in volume, which is the case for a car's cabin vs. the outside world. Automotive heat pumps have a large amount of heat they can capture from "outside" air and a very limited amount of heat they can extract from "inside" air, which is why the standard AC system is used for cabin cooling. It's more efficient.

The small automotive AC compressor is not at all efficient at cooling water, which requires over three thousand times the energy of cooling the same volume of air. That translates to a car's AC compressor taking about 60x as long to lower 2 gallons of water temperature by 1 degree as a 100cf cabin.

The whole SE US uses heats pumps to heat AND cool their homes.

It's not a useful comparison. A multi-ton unit working on large volumes of air and effectively unlimited power doesn't have anything to do with a very small unit running on a very limited power supply.

You also do not want to pull heat from the cabin to dump into the battery when it's cold outside, and when you need to cool the battery, you usually do not want to move that heat into the cabin, so the heat exchange in a car is more complicated than cooling a house.

In newer Tesla MS’s the heat pump cools and heats the cabin and the battery for optimal charging. Why would Porsche not use the heat pumps to provide both cooling and heating capacity for everything in the car? Heat pumps still use fans and radiators.

Teslas and Porsches work the same way. Battery cooling is not needed at all until the battery gets above ~90 degrees F. The fan and the radiator provides all the cooling power needed for the powertrain up until the outside air gets over ~100F.

It is not efficient to use the AC compressor to cool the battery. It takes a lot more power than the water pump and fans and only has a fraction of the cooling power. Just like opening your windows in a breeze will cool the house much faster and with very little power compared to sealing it all up with a single window AC. The AC loop is only used as a backup for conditions where normal radiative cooling of the battery has failed.

On the flip side, there's plenty of heat energy to extract from the air all the way down to about 15F, so using the heat pump for heating is more efficient almost always. This, again, is why automotive heat pumps are more for heating than for cooling anything.

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