Air cooled battery modules

[diamond.g]

Read my earlier post about how the e-NV200 cooling system works. The proposal by the article is essentially the same thing (except cell spacing is much larger and layout is different).
Air cooled battery modules

Basically the connections into the pack is exactly the same with two coolant hoses (one in and one out). The differences are:
- In Model S/X, the coolant is directly run through tubes that touch the cells directly, thus allowing liquid cooling/heating
- In the article, the coolant is run through a radiator in the middle and then fans circulate air through the radiator to cool/heat the cells.

The coolant would already be cooled/heated by the AC/heat recycling system, just like it is with the Model S. So the temperature has nothing to do with ambient air.

What is changed is that instead of using liquid, air is used to interface with the cells. Air has roughly 4x less specific heat than water, so there must be roughly 4x the volume of air moved to provide the same cooling effect. That is the reason the author suggests for larger gaps between the cells.

Shouldn't the cooling system be spec'd for supercharging?

 

[stopcrazypp]

Shouldn't the cooling system be spec'd for supercharging?

Well, the author is saying his proposed system would be designed to have essentially the same cooling effectiveness as the old liquid system by having larger gaps between cells (so there is a larger volume of air) and the blowers/fans can move air the air more quickly. This increase in flow rate of the air will make up for the lower the lower specific heat of air.

 

[JeffK]

Hmmpf, seems mighty inefficient, but I haven't read the whole article (refuse to be required to create an account for such things, when 75% of the screen is already ads and click-bait). Datacenters are moving to liquid cooling in order to not waste the energy moving so much air around. Why should cooling a battery be better the other way?

If you have adblocker you won't see seeking alpha ads and if in chrome you can right click on the text on the first page, hit inspect, then you can see the text of the full article without signing up or clicking through a million pages with two paragraphs per page. Screw seeking alpha, they'll get no revenue from me.

 

[diamond.g]

Well, the author is saying his proposed system would be designed to have essentially the same cooling effectiveness as the old liquid system by having larger gaps between cells (so there is a larger volume of air) and the blowers/fans can move air the air more quickly. This increase in flow rate of the air will make up for the lower the lower specific heat of air.

Aside from Supercharging I wonder how quiet such a system would be.

 

[22522]

From a safety perspective, what they have is pretty good. I don't see how they walk very far away from their safety track record without taking market risk. Would not expect the battery cooling technology change much.

 

[GSP]

I thought of that first reading the title, but if you look at his proposal in detail, actually that part is irrelevant. The interface between the battery and car could be kept the same as in the S today, but instead of running the coolant through the cells, the coolant is only run through the central heat exchanger/radiator.

This is exactly the same way the Nissan e-NV200 active air cooled pack is designed.
Note the two silver coolant tubes near the middle that go to the radiator (on the right of the picture) inside the pack. Then a fan is used to circulate the air through the radiator.

Does Nissan e-NV200 Show Change of Policy on Battery Heating, Cooling?

Maybe this will not seem like an important distinction, but the NV200 cooling system does not look like coolant flowing through a radiator. Instead it looks like the battery has A/C refrigerant piped in, flowing through an expansion valve and evaporator. This sort of system allows heat to be pumped out of the battery to a higher temperature heat sink [basically the definition of A/C]. That is just based at looking at the pictures, so I can't say for sure.

The Ford Escape hybrid has a cooling system like this years ago.

I think that Tesla will probably stick with liquid cooling for the 3, but air cooling is certainly a possibility.

GSP

 

[tsla007]

One word: Never

Why: you can't control the really cold air that come in or hot air. Too much of a change in environment for the cells which kills them.
Now if you could control the air temp-which you can't right now -too much weight and cost involved-it might be wise, but those 2 things need massive tech advances to get there.

 

[garsh]

One word: Never
Why: you can't control the really cold air that come in or hot air.

You really need to read the article before commenting. He's suggesting a sealed battery - no air in or out.

 

[Topher]

Yes, that's why the author proposed not using ambient air, but a sealed chamber with cool air conditioned air.

So the idea is to create cooled liquid (in the AC unit), move it into a heat exchanger to cool some air (a lot more air than liquid), then move the air to the cells, and back to the heat exchanger, to heat the liquid, so it can be moved back to the compressor. Instead of cooling the liquid moving it the cells and back to the compressor. Why does anyone think that is a better solution?

Thank you kindly.

 

[lklundin]

If you have adblocker you won't see seeking alpha ads and if in chrome you can right click on the text on the first page, hit inspect, then you can see the text of the full article without signing up or clicking through a million pages with two paragraphs per page. Screw seeking alpha, they'll get no revenue from me.

I am guessing the problem the poster refers to is that when reading Seeking Alpha on certain smart phones, you are only allowed to read the first part. It then goes on to not only require you to register, but to actually read via their app. Obviously, letting Seeking Alpha execute code on your device is a no go.

If not on a smart phone, then not enabling Javascript may improve the experience.

 

[lklundin]

So the idea is to create cooled liquid (in the AC unit), move it into a heat exchanger to cool some air (a lot more air than liquid), then move the air to the cells, and back to the heat exchanger, to heat the liquid, so it can be moved back to the compressor. Instead of cooling the liquid moving it the cells and back to the compressor. Why does anyone think that is a better solution?

Thank you kindly.

Well, Seeking Alpha contributor, Randy Carlson, who wrote a number of very long but also very insightful analyses of Tesla, thinks so and he explains why

The idea with this thread is to first read his article, and then comment on its specifics.

 

[Topher]

Well, Seeking Alpha contributor, Randy Carlson, who wrote a number of very long but also very insightful analyses of Tesla, thinks so and he explains why

The idea with this thread is to first read his article, and then comment on its specifics.

Read the article. He is still wrong. Your argument from authority doesn't make him less wrong. Guessing the length of the model 3 doesn't make him an expert on HVAC. If YOU have a rebuttal to my argument go ahead and make it.

TL;DR His proposed air cooling system has all the same parts as a liquid cooling system PLUS all the parts to deal with the air, just so it can use an inferior heat transfer medium.

Thank you kindly.

 

[stopcrazypp]

Maybe this will not seem like an important distinction, but the NV200 cooling system does not look like coolant flowing through a radiator. Instead it looks like the battery has A/C refrigerant piped in, flowing through an expansion valve and evaporator. This sort of system allows heat to be pumped out of the battery to a higher temperature heat sink [basically the definition of A/C]. That is just based at looking at the pictures, so I can't say for sure.

The Ford Escape hybrid has a cooling system like this years ago.

I think that Tesla will probably stick with liquid cooling for the 3, but air cooling is certainly a possibility.

GSP

Yes, I was somewhat skeptical of the description too on the article I linked (which says "coolant"). The tubes do look more consistent with refrigerant tubes than coolant tubes, but the idea would be similar (although a refrigerant based system would not be compatible with Tesla's current system).

 

[stopcrazypp]

So the idea is to create cooled liquid (in the AC unit), move it into a heat exchanger to cool some air (a lot more air than liquid), then move the air to the cells, and back to the heat exchanger, to heat the liquid, so it can be moved back to the compressor. Instead of cooling the liquid moving it the cells and back to the compressor. Why does anyone think that is a better solution?

Thank you kindly.

Although not necessarily with the large air gaps he proposes (which increases battery enclosure costs), this type of system has one main advantage: it is cheaper. That is why a bunch of EVs and hybrids have used such a system.

 

[Topher]

Although not necessarily with the large air gaps he proposes (which increases battery enclosure costs), this type of system has one main advantage: it is cheaper. That is why a bunch of EVs and hybrids have used such a system.

It wouldn't be cheaper since it requires more parts.

Nor does any other EV use the system described. They have air system which use ambient temperature air. Hence the problem some of them have seen in hot climates.

Thank you kindly.

 

[gregd]

Exactly.

And don't forget your high school physics... Consuming the several hundred watts (I'm guessing here) in the fans to push that much air around the sealed battery pack, besides consuming the power (range!), just heats up the air. Yes, pushing a water-based coolant around also takes power and heats up the water a bit, but a lot lot less.

 

[stopcrazypp]

It wouldn't be cheaper since it requires more parts.

Nor does any other EV use the system described. They have air system which use ambient temperature air. Hence the problem some of them have seen in hot climates.

Thank you kindly.

I linked the e-NV200 multiple times, which uses a similar system (not ambient air, but conditioned air; although as GSP points out, it might be using refrigerant instead of standard coolant). GSP said the Ford Escape hybrid uses a similar system also.

The cost you save is running coolant tubes to every cell (keep in mind that these aren't the cheap rubber tubes used to route coolant through an engine bay, but rather ribbed metal tubes designed to transfer heat from the cells). If the radiator and fan costs less than that tubing system, then you save money with this design.

 

[JeffK]

I linked the e-NV200 multiple times, which uses a similar system

I don't know that I'd consider the e-NV200 in the same class with the same charge and discharge rates. 0-60 mph in 13 seconds, that's almost sports car territory... err prius territory... hmm not even, I can't think of a car that slow?

 

[diamond.g]

I linked the e-NV200 multiple times, which uses a similar system (not ambient air, but conditioned air; although as GSP points out, it might be using refrigerant instead of standard coolant). GSP said the Ford Escape hybrid uses a similar system also.

The cost you save is running coolant tubes to every cell (keep in mind that these aren't the cheap rubber tubes used to route coolant through an engine bay, but rather ribbed metal tubes designed to transfer heat from the cells). If the radiator and fan costs less than that tubing system, then you save money with this design.

But if that fan has to move supposedly 4 times the air, how much range does that sap?

 

[JeffK]

But if that fan has to move supposedly 4 times the air, how much range does that sap?

Estimated EPA range is only around 72-75mi (105 mi NEDC) so that makes it less efficient than a Model S while being nearly 1000 lbs lighter.

3.5 mi/kWh on Model S vs 3.125 mi/kWh on the e-NV200