Electric cars and cooling drag

[JulianEdgar]

Originally Posted by Isaac Zachary

I think it's going to be hard to quantify the future of BEV cooling when it's still in it's early stages.

• BEV's are more efficient so produce less heat
• But unlike ICEV's they don't have half or more of that heat leaving via the exhaust.
• BEV's also don't have the large temperature differential that ICEV's have, which means that BEV temps necesitate a bigger radiator to remove the same amount of heat.

In most ICEV's you can cool the engine to acceptable temperatures even under full load in 110⁰F/43⁰C dry weather at high altitude with the stock radiator. But put a BEV under the same condition and what kind of cooling system with how much energy loss is going to be needed to keep the battery and inverter at acceptable temperatures?

Just like ICEV's you need a cooling system that can work in pretty much any part of the world. Otherwise you end up with the Nissan Leaf problem. But how small and efficient can that cooling system be made?

You could argue that on most places you don't need a huge radiator to cool a BEV and that the bay could be cooled by a hat pump or flaps that open up more radiator in hot weather. Of course the same technologies could be applied to ICEV's as well.

Good post. When I've talked to car company engineers about ICE car cooling, the issue has always been towing - eg up a long hill at slow road speed. With the coming BEV light trucks (that I understand will be rated for towing) the amount of cooling they will need will be interesting.

[Vekke]

On the ID3 top speed is limited to 160 km/h.

I have designed cooling systems to electric bus Linkker. The radiators have to be bigger due to lower delta T in temperature. Battery max temps can go up to 60 celsius and system needs to be able to keep under about 55c depending what kind of battery chemistry you are using it can be little higher or lower.

Then you know how much heat is generated during top speed driving or in fast charging. Usually the fast charging is the bottle neck as fans can only move certain amount of air.

To get any cooling you need to have large radiator surface area if because outside temp can be even over +40 celsius. So delta T is only low as 15 celcius.

If you know again how you will use your car you can close the front cooling holes little bit like I did in my ID3.

[aerohead]

# 69 permalink lists my sources. They are from the automaker, SAE Papers, other research organs, or automotive periodicals.
Some values were reverse-engineered from quanta provided. Some were derived using the formulas we have at the top of the forum.
Unless specific percentages are presented along with all caveats, I consider them 'trash' information.
Actual road test-derived numbers for the Tesla S will vary as to the specific model of the Model S. They're not all created equal, and performance of one type cannot be attributed to any other variant of the car.
Even the Taycan has two flavors.
And, repeating myself, it's impossible to make an accurate comparison between ICE and BEV cooling drag percentages of any specific vehicle unless you have an ICE and BEV version of the vehicle, along with all pertinent information, like The KONA. There are side-by-side comparisons available for ICE, Hybrid, and BEV versions of that car.
The other elephant in the room is, thermal efficiency variability between ICE and BEV and comparing on a Btu basis.

[JulianEdgar]

Originally Posted by aerohead

# 69 permalink lists my sources. They are from the automaker, SAE Papers, other research organs, or automotive periodicals.
Some values were reverse-engineered from quanta provided. Some were derived using the formulas we have at the top of the forum.
Unless specific percentages are presented along with all caveats, I consider them 'trash' information.
Actual road test-derived numbers for the Tesla S will vary as to the specific model of the Model S. They're not all created equal, and performance of one type cannot be attributed to any other variant of the car.
Even the Taycan has two flavors.
And, repeating myself, it's impossible to make an accurate comparison between ICE and BEV cooling drag percentages of any specific vehicle unless you have an ICE and BEV version of the vehicle, along with all pertinent information, like The KONA. There are side-by-side comparisons available for ICE, Hybrid, and BEV versions of that car.
The other elephant in the room is, thermal efficiency variability between ICE and BEV and comparing on a Btu basis.

No, all just red herrings.

It's very easy to state what the percentage cooling drag of a vehicle is - it's done all the time.

The current evidence shows that the cooling drag of a BEV is no where near zero (in contrast to what you have repeatedly stated).

That's a simple fact, based on the published evidence.

Anything else is just smoke and mirrors - in fact, typical Aerohead obfuscation as he scrabbles to hide his previously posted misinformation.

[freebeard]

The current evidence shows that the cooling drag of a BEV is no where near zero (in contrast to what you have repeatedly stated).

EVs have cooling systems. Q.E.D.

[JulianEdgar]

Originally Posted by freebeard

EVs have cooling systems. Q.E.D.

No, not sufficient evidence.

At least one ICE car had close to zero cooling drag (less than 1 per cent).

[aerohead]

Originally Posted by JulianEdgar

No, all just red herrings.

It's very easy to state what the percentage cooling drag of a vehicle is - it's done all the time.

The current evidence shows that the cooling drag of a BEV is no where near zero (in contrast to what you have repeatedly stated).

That's a simple fact, based on the published evidence.

Anything else is just smoke and mirrors - in fact, typical Aerohead obfuscation as he scrabbles to hide his previously posted misinformation.

1) If you ever publish a single percentage for cooling drag, we'll immediately know that it's bogus. And if I have to explain it to you, we're all in deep..... and underserved, until we can figure out how to pump daylight to you.
2) And as you pursue another crucifixion, it would be fair to submit my exact wording used, which gave you this conclusion. I don't recall ever making such a blanket, all-encompassing comment like that. I just looked at 480-miles of Teslas in the last two days. Their obvious, 1963 Walter Korff race car minimum nose porosity makes me, if no one else, ponder their drag savings. You yourself mentioned that it is a simple matter of blocking this inlet to measure the cooling drag.
3) You have data for two vehicles? One Porsche and one Tesla? Radiators sized for 160-mph and 155-mph respectively. You are aware that there are two Taycans? And perhaps seven Model S ? And would you like to tell us all what their cooling drag would be if they were designed for 66-mph top speed? I've already given you some strong clues.
When you come up with data for the Mitsubishi i-MiEV get back to us. Chevy SPARK. SMART ED. FIAT 500e.
If you're going to play the prosecutor, at least learn the part!
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When you finally know what you don't know about cooling systems, you'll be at a great starting place for taking on the topic.
The pedantry ain't cutting it.

[JulianEdgar]

Originally Posted by aerohead

1) If you ever publish a single percentage for cooling drag, we'll immediately know that it's bogus. And if I have to explain it to you, we're all in deep..... and underserved, until we can figure out how to pump daylight to you.
2) And as you pursue another crucifixion, it would be fair to submit my exact wording used, which gave you this conclusion. I don't recall ever making such a blanket, all-encompassing comment like that. I just looked at 480-miles of Teslas in the last two days. Their obvious, 1963 Walter Korff race car minimum nose porosity makes me, if no one else, ponder their drag savings. You yourself mentioned that it is a simple matter of blocking this inlet to measure the cooling drag.
3) You have data for two vehicles? One Porsche and one Tesla? Radiators sized for 160-mph and 155-mph respectively. You are aware that there are two Taycans? And perhaps seven Model S ? And would you like to tell us all what their cooling drag would be if they were designed for 66-mph top speed? I've already given you some strong clues.
When you come up with data for the Mitsubishi i-MiEV get back to us. Chevy SPARK. SMART ED. FIAT 500e.
If you're going to play the prosecutor, at least learn the part!
-------------------------------------------------------------------------------------
When you finally know what you don't know about cooling systems, you'll be at a great starting place for taking on the topic.
The pedantry ain't cutting it.

[Groan] More smoke and mirrors.

Single figures for cooling drag are published for cars all the time - maybe do a literature search?

You've often stated that a car had such a and such a drag figure, and if it were electric, then it would have a [much lower] figure. Maybe you've forgotten what you've written?

Never mind. We all know now to point out the error when you repeat it.

[aerohead]

Originally Posted by JulianEdgar

[Groan] More smoke and mirrors.

Single figures for cooling drag are published for cars all the time - maybe do a literature search?

You've often stated that a car had such a and such a drag figure, and if it were electric, then it would have a [much lower] figure. Maybe you've forgotten what you've written?

Never mind. We all know now to point out the error when you repeat it.

1) cooling systems free of shutters would be within bounds for a single quanta. The authors would be obligated to state the conditions.
2) any vehicle with shutters must be reported as a 'range' of percentage. By default, it cannot be a single value.
3) if active air-suspension is part of the mix, the vehicle must be reported for the range of body height.
4) if the vehicle has an active airdam, ditto.
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*As to 'often reported' I'm referring to garden variety, family passenger cars, not sports cars, high performance sports cars, or supercars.
* Your Taycan and Model S are not germane to passenger cars due to their maximum attainable velocities.
* You know that aerodynamic drag power requirements vary with the cube of the velocity.
* You must also know that if you're cooling a motor or batteries, that the aerodynamic portion of that cooling load will also vary as the cube of the velocity.
* 155- cubed, divided by 77.5-cubed will give you the difference in radiator size for the aerodynamic power-related cooling load for the Tesla Model S at theses two speeds. Some BEVs won't even go 77.5-mph! This is part of the 'context' which must be part of the discussion, or else it borders on complete intellectual dishonesty.
* The percentages you have for both Tesla and Porsche had better have this kind of information or it will be completely useless!
* God lives in the details.
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a) Some of your own shared materials imply that air-cooled battery BEVs could enjoy a Cd 0.025 advantage as far as losing the conventional cooling system, plus Cd 0.010 advantage of a smooth belly pan. A Cd 0.035 advantage.
b) If you take your Porsche Taycan Turbo, at Cd 0.22, and add back Cd 0.035, you get Cd 0.255, about as good as the 1975 Ferrari Cr 25. This is the 'CONTEXT' of my comments.
c) we can say, Gee, look at how low the drag is on that Taycan. Or we can say ' Ho -hum, yeah, we saw that forty-five years ago.'
d) this is 'CONTEXT'.
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Bjorn Nyland reported his Autobahn-test Tesla Model S results. Low and high performance variants. Watts/ mile vary by 40% between the two Model S's. Radiator sizes could vary 40%. Cooling drag could vary 40%.
Your paper needs to parse this sort of thing out! CONTEXT!
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If you've been given privileged materials under the condition that certain information not be disclosed as a condition of the 'giving', this may lead to unresolvable 'push-back' issues.
All I can say is that, the more info the better. There's no such thing as 'too much.'

[JulianEdgar]

Originally Posted by aerohead

* You know that aerodynamic drag power requirements vary with the cube of the velocity.
* You must also know that if you're cooling a motor or batteries, that the aerodynamic portion of that cooling load will also vary as the cube of the velocity.
* 155- cubed, divided by 77.5-cubed will give you the difference in radiator size for the aerodynamic power-related cooling load for the Tesla Model S at theses two speeds. Some BEVs won't even go 77.5-mph! This is part of the 'context' which must be part of the discussion, or else it borders on complete intellectual dishonesty.
* The percentages you have for both Tesla and Porsche had better have this kind of information or it will be completely useless!
* God lives in the details.

None of that is relevant when we are talking about the drag coefficient penalty of cooling systems!

Like, it's why we use coefficients not absolute values.

If you think we need to be measuring speed, I guess that's one reason you're confused regarding the idea of cooling system drag as a percentage of the total drag coefficient.