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Comment by vel0city

21 hours ago

> The main issue with prismatic cells is that to be safe, they must be made with LFP chemistry, which hurts energy density

This is obviously untrue. Tons of other chemistries have used prismatic cells with good safety as well. You think Macbooks and iPhones use LFP or cylinder cells?

> Batteries with cylindrical cells were easier to repair,

It can be just as easy to repair a prismatic battery as a cylinder battery. It all comes down to the layout of the battery. And as you mentioned, how the battery is constructed, if the battery is structural, etc.

9 comments

vel0city

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ggreer  17 hours ago

Since this is a discussion about electric vehicles, I thought it could go without saying that I was talking about batteries in such vehicles, not batteries in consumer electronics that are 1,000 times smaller.

To use an analogy: If someone stores a gallon of gasoline in a single-walled plastic container, that's probably OK. But storing 1,000 gallons of gasoline without certain safety measures is unsafe. So it goes with battery capacities.

  • formerly_proven  9 hours ago

    Apart from Tesla very few EVs ever used cylindrical cells.

    • ggreer  1 hour ago

      My point was about cylindrical cells with higher energy chemistries like NMC and NCA. Rivian uses cylindrical cells for their non-LFP batteries. Lucid uses 2170 cells. As far as I can tell, those three (Tesla, Rivian, Lucid) are the only US car manufacturers who have not had battery recalls due to fire risk.

      GM, Hyundai, and Nissan all used pouch cells with higher energy density chemistries, and had recalls due to battery fire risks. Ford also recalled tens of thousands of their plug in hybrids due to battery fire risks, though they haven't found a solution yet beyond limiting the max charge of the battery. These batteries are also NMC pouch cells.

      I'm sure it's physically possible to make safe, reliable pouch or prismatic cells using higher energy chemistries, but so far it has been risky for those who have tried.

  • vel0city  14 hours ago

    But it still is untrue even in the discussion of electric vehicles. Tons of EVs have been made safely with chemistries other than LFP with prismatic cells. In fact most non-LFP EV batteries are pouch or prismatic, not cylinder.