It's the Batteries, Stupid!

[JRP3]

One of the more ridiculous battery "solutions" I've seen:

This Company May Have Solved the Electric Car Charging Problem

 

[Electroman]

Is this a spoof..? I can't tell..

 

[ggr]

Is this a spoof..? I can't tell..

Having done a bit of work in ad-hoc networking, I think there is at least a germ of a good idea there. Practical issues might get in the way though, like getting good contact between the cells, or them moving around when you hit a bump. I don't think it's a spoof, but I won't be investing either

 

[M0DEL³]

One of the more ridiculous battery "solutions" I've seen:
This Company May Have Solved the Electric Car Charging Problem

The accumulative efficiency losses of this model would be massive. Just the loss caused by density restrictions from cooling concerns would be problematic. Would be extremely surprised if the volume of a MS battery pack could offer half the net range of a Nissan Leaf with this system model. All that being said it certainly scores brownie points for creative out of the box thinking - if this ever makes it to a production prototype stage, that alone would be astounding.

 

[Electroman]

If I can only drive 150 miles and fill it up in 5 minutes.. that sure enables long distance driving..

The fact that it can pair up cells with equal voltage is a great benefit which removes the need to do active 'in-car' balancing to a large extent.

 

[JRP3]

The fact that it can pair up cells with equal voltage is a great benefit which removes the need to do active 'in-car' balancing to a large extent.

With current cell production quality there isn't that much balancing going on anyway, so I don't see that as any real world advantage. I think the fact that all the electronics in each of those football batteries has to be hardened against the shock loads of being vacuumed in and out of their containers would cancel any possible savings.

 

[AC1K]

I put all my money on ultra capacitors for what the future decides on the best type of energy storage.

 

[BluestarE3]

Is this a spoof..? I can't tell..

Yeah, that battery vacuum reminds me of the SNL spoof of the Mercedes AA from last week where pulling the battery release tab ejects all the Duracells from the car.

If people are concerned about getting someone else's degraded battery pack in a battery swap station (Telsa's solution is to require you to swap back to your own pack on your return trip), imagine how many potentially degraded cells you may end up with when you are force-fed thousands of these at the refueling station. Or does the fancy internal electronics weed out the bad ones during recharging so they are shunted off to a "reject" bin and not get back into the "feed" bin?

 

[Intl Professor]

Randy Carlson has an interesting battery discussion which may have already been discussed on this thread.

http://seekingalpha.com/article/3983102-teslas-gigafactory-christmas-july#alt2

 

[Cosmacelf]

Wow, what a great Seeking Alpha link. The article (and the author's earlier article where he shows that Tesla is likely moving to a closed circuit air cooled battery pack instead of their current liquid cooled pack) shows how Tesla can save 15% battery cost just from a cell/pack manufacturing simplification, and wrest more capacity from their packs as well.

It is a complex article, but well worth the read. If this innovation is accurate, Tesla once again has technology no one will be able to touch for a decade (Supercharger network being the other competitive advantage that no one is looking to replicate).

 

[JRP3]

I'm fairly sure Randy is completely wrong about the air cooled pack for a number of reasons. Starting with his under estimation of pack kWh's in previous articles, (44kWh for the base pack is not going to happen), and his insistence on drawing conclusions from a somewhat blurry CG image of the battery pack at the Model 3 reveal. Not to mention his idea that Tesla will take a cell fresh off the production line and immediately stick it into a module, and then if it might fail pull that cell back out of a module and replace it. He ignores the necessary aging that new cells must go through along with capacity and resistance testing, along with the coulombic efficiency testing developed by Prof. Dahn that can accurately predict how a cell will perform. He's also speculating about a larger than reasonable jump in specific energy, but if he were to be correct, that, along with the larger format cylindrical cells, would likely require more aggressive cooling, which liquid would provide, but air would not. I think this is one of the worst articles Randy has ever done and am 99% sure Tesla will not use his proposed cooling scheme.

 

[Cosmacelf]

Jrp3, he doesn't ignore the aging and testing, he says that it can be done in the car rather than spend $500M in capex to do it in the factory. He might be wrong about the individual cell replacement (I think bad cells would just be handled statistically, and left in there as bad cells -ie you plan for a certain number of cells to be bad).

A very salient piece of evidence is that Tesla is going to take over ownership of emergency stock in the form of battery packs, rather than Panasonic having to keep cell emergency stock. Why would you change this unless you had to? To me that points to Panasonic not being able to produce cells without a finishing step in the pack.

The rest of your points are just assertions with no backup (i.e. That refrigerated high velocity air cannot cool the packs. Really?)

 

[JRP3]

Physics backs up my statements. It's not that refrigerated air can't cool the packs, it's that it can't do it as well as a liquid, and it takes more volume to do it. That means Tesla would need to build a taller vehicle, which means greater air resistance, which means less efficiency, exactly the opposite of what Tesla wants with the Model 3. Plus the concept of aging and testing a cell in the pack is frankly insane.
I don't remember seeing Tesla taking emergency stock in the form of packs, I'd like to see where that was stated by Tesla or Panasonic.

 

[Electroman]

It's not that refrigerated air can't cool the packs, it's that it can't do it as well as a liquid,

I am not too sure about that. Remember if the cells are immersed in a coolant liquid like the Uranium rods in a nuclear reactor, I fully get what you are saying. But coolant liquid is sent through pipes which snakes around the cells. You can cover more area with cold air blowing rather than a cold pipe, which would not leave any hotspots.

 

[scaesare]

I am not too sure about that. Remember if the cells are immersed in a coolant liquid like the Uranium rods in a nuclear reactor, I fully get what you are saying. But coolant liquid is sent through pipes which snakes around the cells. You can cover more area with cold air blowing rather than a cold pipe, which would not leave any hotspots.

However liquid is far denser than air, and thus can provide greater cooling capacity per unit of volume.

This is why, for most densely packaged items (like engines) you see liquid cooling even though the coolant passages are far smaller than the equivalent surface area you might be able to blow air over.

 

[bkp_duke]

/facepalm

OK guys, being a chemistry major this just HURTS me to remind you, but water-based liquids, especially those based upon water have a MUCH HIGHER heat capacity than air.

specific heat

This is why water-based solutions (anti-freeze) are used in radiators instead of air. The air-to-water interface portion of the radiator has to be approximately 4 times the size of water-to-engine interface to dissipate the same heat.

Science fact, not room for debate on this one.

 

[Cosmacelf]

[QUOTE="JRP3, post: 1592439, member: 630] I don't remember seeing Tesla taking emergency stock in the form of packs, I'd like to see where that was stated by Tesla or Panasonic.[/QUOTE]

From a recent Tesla 10Q:

As a Tesla responsibility and during the Term, Tesla shall hold a safety stock consisting of [***] (the "Safety Stock"). Tesla may use the Safety Stock to accommodate fluctuations in Tesla's actual requirements, to mitigate potential damages resulting from Seller's failure or inability to deliver the Goods in accordance with the Contract, and for other reasons determined by Tesla from time to time. [***].

This is part of the gigafactory agreement with Panasonic. I don't have time to chase down the link to the 10Q, but this excerpt came from a link referenced in the original article.

 

[JRP3]

Safety stock seems to refer to cells, not packs.

 

[Cosmacelf]

Safety stock seems to refer to cells, not packs.

You can't tell either way, I believe. The first redaction [***] says what the safety stock consists of, and it is interesting that it is redacted. The redaction could specify the number of cells, or it could say a number of packs with partially finished cells. We don't know. It's just one piece of the puzzle/evidence.

The original pricing proposal didn't have any mention of safety stock, nor would I have expected it to - Panasonic would, as a matter of course, keep battery cell inventory available on hand in case of production difficulties to meet the demand. The original agreement implicitly binds Panasonic to keep a safety stock since they would be in default if they had production difficulties. The fact that Tesla is now taking on that responsibility is intriguing.

If you look at the rest of the amendments (Tesla Motors - Quarterly Report, search for "safety stock"), it is lawyers tightening up language for corner cases in case Tesla or Panasonic gets sold. This one amendment is unique in that it changes the operating agreement between Tesla and Panasonic in a material way.

The original article author pulls other pieces of evidence. Remember when the gigafactory construction was halted, and some portions reconstructed? We never got an explanation for that (or I missed it if Tesla actually said anything about it). The reason for that rather unusual pause might have been Tesla/Panasonic deciding to build cells/packs differently and thus they needed a slightly different building configuration.

 

[woof]

It's conceivable that instead of "air" they might end up using Direct Expansion of coolant ala BMW. (Sorry for the click-bait headline, the article is actually pretty good)
BMW and LG Chem Trump Tesla in Battery Thermal Management - HybridCars.com

Simpler, better heat transfer, and lower cost. What’s not to like?

Will we see this DX cold plate cooling scheme in the new Chevy Bolt and the Tesla Model 3? We predict yes.