Pouch vs Prismatic battery cells - VW announcing their intent to change

Dudd

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So, the Mach E uses pouch type battery cells. Recently Volkswagen announced they are moving away from pouch to prismatic cells, like the ones in your phone. I don't know much about such things but after 5 minutes of googling I can't see an advantage to this move other than perhaps cost? Just throwing this out there in case anyone that actually knows anything about this topic wants to comment :)

This article cites safety due to lower energy density: Volkswagen may switch from pouch to prismatic battery cells | Autoblog

Is that really true? I can find other articles saying pouch style is safer because it can expand, so is less likely to explode anyway. Pouch appears to be lighter, smaller and more versatile, so later VW EVs will have bigger and heavier batteries? That is the wrong type of evolution.....

In the meantime I think that leaves me happy with the pouch batteries in the Mach E :)

With regards to energy density they don't seem to factor in the intrinsic dangers of filling ICE vehicles with petrol....





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malba2366

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I dunno about the benefits, but the stock market loves it. VW stock up 40% since their battery day event.
 
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I dunno about the benefits, but the stock market loves it. VW stock up 40% since their battery day event.
I imagine that's because they announced spending a tonne of money on charging infrastructure in US and Europe as well as driving towards future solid state batteries.

The Prismatic battery technology notification does mean they will be targeting cheaper, heavier and less powerful electric cars i.e. much more mainstream than the Mach E, so that would likely have boosted the share price a little too.

I can't see any technical benefits with a prismatic battery that are relevant to a more sporty car like the Mach E. i.e. Bulkier and heavier with lower energy density are a distinct disadvantage in that sort of competition.
 

malba2366

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I imagine that's because they announced spending a tonne of money on charging infrastructure in US and Europe as well as driving towards future solid state batteries.

The Prismatic battery technology notification does mean they will be targeting cheaper, heavier and less powerful electric cars i.e. much more mainstream than the Mach E, so that would likely have boosted the share price a little too.

I can't see any technical benefits with a prismatic battery that are relevant to a more sporty car like the Mach E. i.e. Bulkier and heavier with lower energy density are a distinct disadvantage in that sort of competition.

Once charging builds out, most EVs in the mainstream price points will have smaller batteries. Only the expensive ones will have the 300+ mile ranges.
 

62Lincoln

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VW announced its plan to build a total of 6 battery cell factories in Europe during this decade with a total output of 240GWh - 2 are already under construction. This assures them of supply for their sales plans (at least in Europe) and also cut out the Korean battery companies (LG and SK) who are warring with one another over patent infringement.

VW spoke of cost reduction, which mirrors malba2366's post above. Quite a bit of the marketplace in Europe are smaller, urban vehicles, so the point about smaller battery footprints for these less expensive vehicles is point on.

The march to solid batteries is continuing, so VW must have an eye towards that technology later this decade.
 
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Dudd

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So.... all very interesting but my original question was about advantages/disadvantages between prismatic and pouch style batteries...
 
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Dudd

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As far as I can see none of those links speak to EV applications, commercial advantage to VW with regards to their decision to move to Prismatic and whether there is an advantage other than being able to build cheaper EVs with worse performance characteristics.
 

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In the stationary storage industry we prefer prismatic cells, because while they may have a tiny bit lower energy density, that doesn't matter much when you are building on a 10 acre site. The plus of prismatic cells is that they hold the electrolyte in with a lot more pressure - the tendency to puff is a problem with pouch cells (not a feature). Cylindrical cells also have a lot of internal pressure, but the round shape means you lose a lot of space around each cell. Prismatic gets you the internal pressure in a pack-able shape.

Over time, that internal pressure helps prevent degradation because the internal cell materials can't expand and contract as much during operation. In the event of a failure, prismatic cells usually have a vent that pops open to release the gas, preventing an explosion.

On EVs, the value of energy density is higher, so the compromise may get tilted more toward the pouch direction again. All features of batteries are compromises - there is no perfect combination right now, you just have to balance, density, cost, longevity and weight and find something that works for your application.
 

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other than being able to build cheaper EVs
What more advantage do you think a company needs than cost? If both options "work" then cost is what matters most. Plenty of superior technologies have died due to cheaper good enough alternatives.
 
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Dudd

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What more advantage do you think a company needs than cost?
Well, cheap doesn't mean good. Of course there needs to be lots of cheaper more poorly performing cars for the mass market, so I'm sure that cheap will be great for VW who will look to fill that niche. In particular though I was seeking further knowledge to get a better understanding as to whether the pouch style batteries in the Mach E are a disadvantage compared to the Prismatic batteries, but I couldn't see too much evidence in that direction.
 

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It seems counter-intuitive, but cylindrical cells have been the winners for most uses.
They are much easier to build, and result in a longer-lasting pack.

The cylinder (circle) packing density is obviously lower, but at over 90% (0.9069) the impact is lower than most people intuit. And if the voids provide required cooling, the overall density impact is minimal. (This is primarily for large packs. For small cell counts the packing density could be lower, and cooling might not be needed.)

What isn't as obvious is that pouch and prismatic cells tend to have higher edge and corner area. These are problematic for layer alignment during construction, and nonhomogeneous chemistry during use.
 

dbsb3233

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Once charging builds out, most EVs in the mainstream price points will have smaller batteries. Only the expensive ones will have the 300+ mile ranges.
Well, somewhat. Frequent charging is a pretty big negative when trying to drive 600 miles in a day. Plus there's the highway speed penalty. And the cold penalty. And the slow charging in the upper quarter of the battery penalty.

Even in the 300 mile MME, realistic 10-80% range at 75 MPH in 40F temps is closer to 150 miles.

If you drop the starting range to 200, now you're down to around 100 on each road trip leg (beyond the first leg where people usually charge to 100% at home). That's 5 stops of probably 20-40 minutes each in a 600 mile day. Each taking time for a detour off the highway to the charger and back. A lot of people won't put up with that much extra churn time.
 

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