Rumor: GM May Use Cylindrical Cells in Future EV Models
- Thread starter E365
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Prior to my retirement I worked closely with our engineering staff who were constantly experimenting with battery designs. They tried prismatic cells and pouch cells and explained to me (in a way that my non-engineer brain could understand) that prismatic and pouch cells had some advantages under certain applications, cylindrical cells were the way to go for automotive applications. And they spent a lot of time on things like the electrode composition and manufacturing techniques. That is why for the moment at least, Tesla has the best batteries.
Whether or not it is still true in another 10 years remains to be seen. We may see some huge breakthrough. But for now, the focus is on making the batteries lighter and smaller and having more range and being as inexpensive to manufacture through the use of materials and manufacturing techniques as possible.
Whether or not it is still true in another 10 years remains to be seen. We may see some huge breakthrough. But for now, the focus is on making the batteries lighter and smaller and having more range and being as inexpensive to manufacture through the use of materials and manufacturing techniques as possible.
https://www.designnews.com/automoti...any acknowledged that the,at risk for a fire.
Funny. Seems LG Chem has claimed they messed up is all.
https://www.caranddriver.com/news/a37552121/chevy-bolt-battery-recall-deep-dive-details/
GM says other things.
GM says it has identified two different manufacturing defects.
Those variable use conditions combine to produce a different pattern of heating and cooling for virtually every Bolt EV pack. Perhaps, Kamath said, only some sets of repeated use conditions exacerbated the pair of manufacturing flaws—one of which may have occurred at a considerably higher rate than expected—to the point where the cell’s expansion and contraction caused a short.
JHZR2
Staff member
I think it should be noted, Tesla’s LFP packs are prismatic cells, not cylindrical. Even Tesla doesn’t demand cylindrical cells. In Q1 2022 nearly half the cars they made had prismatic LFP cells.
https://cleantechnica.com/2022/04/21/half-of-all-teslas-manufactured-in-q1-have-lfp-batteries/amp/
https://cleantechnica.com/2022/04/21/half-of-all-teslas-manufactured-in-q1-have-lfp-batteries/amp/
JHZR2
Staff member
The BMW situation is likely due to balancing. Low and slow allows active BMS balancing to draw down the higher cells. This takes time. Significantly out of balance cells can take forever to rebalance, or in some cases never recover. High rate charge will exasperate the discrepancies in cell and pack impedances. Makes total sense. Balancing too fast/hard is a thermal issue. Recycling the power from high to low cells is a complexity issue.
Thermal management undermines energy density. So no doubt that Ford does that. It takes a lot to get the I2R heating out.
As for GM, IMO/IME the cylindrical cells are a superior product if they are sealed properly. And the Mylar pouch cells aren’t exactly the ideal thermal management case…
This is the shanghai produced car ONLY.
LFP and prismatic aren't synonymous - tesla also uses LFP cylindrical.
Im pretty sure Telsa was informed about how they felt about using CATL as the supplier in this instance.
I’m not suggesting they are. Just that I’ve seen zero reference that Tesla uses LFP cylindrical. (Do you have one?)
This article says, at least early-on, the Standard Range LFP cars in the USA were getting their cells from China.
https://electrek.co/2021/10/21/tesl...-to-lfp-cells-fremont-cell-production-closer/
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It's not a direct reference but a picture of cylindricals in an LFP article.
https://electrek.co/2022/04/22/tesla-using-cobalt-free-lfp-batteries-in-half-new-cars-produced/
LFP packs also negates the "cobalt" child labor argument - odd though, people were never concerned about the same child labor mining platinum, palladium and a host of other rare earths they consume.
JHZR2
Staff member
It isn’t good practice to replace a pouch. Maybe the process of de welding the pouch tabs from a conector
Is easier than a ton of small cells, but that’s why larger cells are desired.
Replacing a cell is asking for trouble.
Yeah - thats going to mess with the balance - unless you can find one aged similarly.
Report: GM To Partner With Samsung SDI On Cylindrical Batteries
https://insideevs.com/news/656051/gm-samsung-sdi-cylindrical-batteries/
JHZR2
Staff member
It is worth noting that the Chevy Volt is also
experiencing battery failures. they were designed for high cycles, but now seem to age out.
experiencing battery failures. they were designed for high cycles, but now seem to age out.
Pouches are fine. Some company's designs, are not.
https://cleantechnica.com/2022/09/21/surprise-nissan-leaf-batteries-last-much-longer-than-expected/
https://www.greentecauto.com/hybrid...teries/nissan-leaf/nissan-leaf-battery-module
The original usable AH per module was about 43. These appear to offer 34-38. That places them at near 80% SoH. I'd say that's excellent for over a decade old, and in a pack with only air cooling, and no fan to supplement.
https://cleantechnica.com/2022/09/21/surprise-nissan-leaf-batteries-last-much-longer-than-expected/
https://www.greentecauto.com/hybrid...teries/nissan-leaf/nissan-leaf-battery-module
The original usable AH per module was about 43. These appear to offer 34-38. That places them at near 80% SoH. I'd say that's excellent for over a decade old, and in a pack with only air cooling, and no fan to supplement.
For pure durability reasons, cylinder is best. For packaging reasons, pouch is best. Good pouches last just fine. Good cylinders last just fine. Pouch cells have the advantage of very low internal resistance, as well. A PROPERLY designed pouch pack is superior, IMO. It is also much more modular. Ultimately, though, buy a warranty. Anything can happen. Just like with turbos or the hundreds of sliding, spinning surfaces in a gas burner.
AFAIK, Nissan is using the similar pouch cells in the Leaf and maybe Ariya - and the former is air-cooled. The metal tube with cylindrical cells also is a better conductor of heat.
Pouch cells are better for high-density/low-draw like cell phones and laptops, but even so, spicy pillows are common there. Cylindrical cells have a big benefit of keeping a BOM simpler.
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