Electric cars and cooling drag

[aerohead]

Originally Posted by JulianEdgar

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.

1) You are absolutely correct within a very narrow reading.
2) What may escape us is, that the cooling load itself will also vary geometrically with velocity, and must be parameterized specifically to the operational envelope.
3) The motor/battery cooling percentage of overall drag for the Tesla Model S, at 77.5 miles per hour would be 1%, instead of 8%.
4) The Taycan Turbo S would be 2% at 80-mph, instead of 16%.
5) If the Taycan and Model S were not designed for 160/155 mph, we'd never see the 16% and 8% values. Their radiators could be 1/8th the size that they are and easily cover the Btus coming their way. This fact is hiding in plain view.

[JulianEdgar]

Originally Posted by aerohead

1) You are absolutely correct within a very narrow reading.
2) What may escape us is, that the cooling load itself will also vary geometrically with velocity, and must be parameterized specifically to the operational envelope.
3) The motor/battery cooling percentage of overall drag for the Tesla Model S, at 77.5 miles per hour would be 1%, instead of 8%.
4) The Taycan Turbo S would be 2% at 80-mph, instead of 16%.
5) If the Taycan and Model S were not designed for 160/155 mph, we'd never see the 16% and 8% values. Their radiators could be 1/8th the size that they are and easily cover the Btus coming their way. This fact is hiding in plain view.

Now you are just making stuff up. I go on the actual, published literature, not my own theories.

And the actual, published literature shows that the cooling drag of BEVs is nowhere near zero, as you have previously claimed.

You can devise whatever figures you want, but until you quote published data of cooling drag percentage on a current BEV that doesn't support what I have said, it simply counts for nothing.

[freebeard]

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

Which one would that be? The Bug?


roadkillcustoms.com/the-bug-iconic-hot-rod-dick-kraft/

[JulianEdgar]

Originally Posted by freebeard

Which one would that be? The Bug?


roadkillcustoms.com/the-bug-iconic-hot-rod-dick-kraft/

No, one of the water-cooled 911 Porsches.

[aerohead]

Originally Posted by JulianEdgar

Now you are just making stuff up. I go on the actual, published literature, not my own theories.

And the actual, published literature shows that the cooling drag of BEVs is nowhere near zero, as you have previously claimed.

You can devise whatever figures you want, but until you quote published data of cooling drag percentage on a current BEV that doesn't support what I have said, it simply counts for nothing.

1) your published data is contextual. Without context it's rubbish.
2) fairness would require that you provide any example of a post by myself, in which I made a claim about 'near zero'.
3) I have a carpet graph which depicts road load for any CdA and velocity.
4) It's quite straight forward to calculate heat flux for a cooling system, for any prime mover, regardless of type and 'fuel' source.
5) you're published data will remain unconvincing, unless the manufacturer who is the source, provides back-to-back comparisons of the specific BEV vehicle, and it's ICE variant, like the Golf, Kona, SMART, Soul, Spark, Niro, Fit, RAV4, etc..
6) everything I've posted is scientifically correct. Your task is to provide counterfactual evidence which overturns the thermodynamics of the situation. Perhaps one of your network members can walk you through it. Have fun!

[aerohead]

Ah yes, the famous 'adiabatic' Porsche.

[aerohead]

https://www.researchgate.net/publica...he_911_Carrera
I read it in it's entirety.
It confirms everything I've mentioned.
Very contextual:
1) ' improved radiator' ( non-aerodynamic variable )
2) ' throttling ' ( a Cd 'spectrum' )
3) ' elastic coolant-temperature target' ( non-aerodynamic variable )
4) ' blower-assisted operation ' ( no accounting for engine-to-alternator-to-battery-to-blower fan power consumption )
5) ' cooling-air drag drops proportionately to the cooling-air volume flow rate'
( extremely germane to the BEVs which have been selected for comparison to ICE vehicles ) [ there are twelve different Tesla Model S variations. All twelve need to be included in the comparison ]
Depending on driving velocity, no doubt, some BEVs will demonstrate lower cooling drag than 1.4% of overall drag.

[ME_Andy]

The numbers Aerohead gave on Spark EV vs Spark ICE drag should have been enough to put this thread to rest a long time ago.

As well as the fact that a 214 hp Nissan Leaf does not (or hardly?) requires drive train cooling. I know the batteries do not need cooling, perhaps the motor requires a bit of cooling.

This is just common sense.

I suspect the initial, shocking claims were made in an attempt to stir up controversy -- and it worked!

[aerohead]

Originally Posted by ME_Andy

The numbers Aerohead gave on Spark EV vs Spark ICE drag should have been enough to put this thread to rest a long time ago.

As well as the fact that a 214 hp Nissan Leaf does not (or hardly?) requires drive train cooling. I know the batteries do not need cooling, perhaps the motor requires a bit of cooling.

This is just common sense.

I suspect the initial, shocking claims were made in an attempt to stir up controversy -- and it worked!

I'd blame Dr. Wolf for some of the confusion. While he 'mentioned' some of the caveats, and actually provided quanta for the 'improved radiator', he failed to account for the ' blower-assisted ' losses and full chain of custody for entropy.
The other sticking point for me is that, in using the Tesla Model S, we may be talking about the 155-mph versions, while the 110-mph version goes unmentioned. The heat flux variability between the two velocities, cooling system size, and associated drag, is geometrically different, and if left unmentioned, would fall way short of serving the student.
A simple comparison of the cubes of the two velocities will tell the tale.

[Isaac Zachary]

Originally Posted by ME_Andy

I know the batteries do not need cooling...

This is just common sense...

shocking claims were made in an attempt to stir up controversy...

Um, excuse me here. But that is controversial.

Here's the thing, you could take any modern day EV (Tesla, Bolt, Leaf, you name it) and take out all the cooling (pumps, fans, etc.) and block the air intakes making the cooling system (or lack thereof) have 0 effect on drag. And you can even daily drive an EV like that in Arizona!

But... If you do that you're now sentencing the car to a short life. Speaking of Nissan Leafs not needing cooling, are you saying you're not aware of the controversy (batterygate)? Have you ever owned a Leaf? Have you ever had the experience of watching your battery capacity fade away? I have, and that's part of the reason I got rid of my Leaf and went back to an ICE car.

Until we figure out how to get batteries to tolerate lots of heat they need a lot of cooling, especially in +100° weather. Ideally you don't want your battery to be much more than 70°F. But there's no radiator big enough to cool a battery to that temperature even in 70°F weather. Even in 65°F it would take an enormous radiator to cool a battery to 70°F even if the car is driven and charged under average driving speeds and distances.

So then what? Heat pump cooling?

There are way too many factors to say how much cooling is acceptable on an EV.

• One person in Anchorage might not understand why there's any cooling at all.
• Someone else in Phoenix isn't going to understand why there isn't more cooling on the same car.
• One person might be happy with a battery that lasts 5 years, or even less as long as the manufacturer will replace it under warranty.
• Another might be wishing his 10 year old used EV will last another 10 years before needing a $9,000-$18,000 battery.
• Because of this one person might feel that an EV doesn't need hardly any cooling (and therefore drag caused from cooling).
• But someone else may wish their car had a much bigger cooling system (potentially much bigger than one an a typical ICE car that causes even more drag).

Ideally we want EV's to perform as well as, if not better than, ICEV's in practical terms. Gaining a couple percent of drag efficiency isn't going to mean much to the average consumer. Longevity and operating costs will.