This is fairly relevant given the huge LG Chem recalls, but there was an article with excerpt from the recent book about Tesla's history, that describes how Tesla designed the pack in the Roadster to avoid one defective cell leading to the entire pack catching on fire.
Key point:
I would take with a grain of salt what was quoted as said or the people involved (given some accounts from the book have been disputed, for example Tim Cook ever talking with Elon Musk), but the general idea matches the pack design Tesla ended up with.
Saw this linked in some discussion about Bolt's pack design (which extends to other pack designs using similar cells). Basically with the large cell designs, while the probability of a single cell catching fire may be lower (due to lower amount of cells), due to the size of the cells, being in a pouch with no solid metal housing per cell, and how they are packed together, a single defective cell pretty much guarantees at least an entire module catches on fire, if not the whole pack.
Other factors that may come into play with LG's case specifically is the higher energy density and chemistry type (NMC). The Bolt had 60kWh with 288 cells or 208 Wh/cell, and the Kona Electric had 64kWh with 294 cells or 218 Wh/cell. The Volt had a similar cell design, but used LMO and only 16kWh from 288 cells, or 56 Wh/cell. The Leaf had 24 kWh LMO and 192 cells or 125 Wh/cell
The other factor may be LG's patented stack and fold design. This may introduce defects that happen only after the cell layers have been put into the pouch and would not be easy to catch with QC (would probably need X-raying each cell). Leaf used a more conventional stack design which probably is less susceptible to this kind of defect.
Key point:
Hitting the Books: How Tesla engineers solved the problem of exploding EV batteries | Engadget
I would take with a grain of salt what was quoted as said or the people involved (given some accounts from the book have been disputed, for example Tim Cook ever talking with Elon Musk), but the general idea matches the pack design Tesla ended up with.
Saw this linked in some discussion about Bolt's pack design (which extends to other pack designs using similar cells). Basically with the large cell designs, while the probability of a single cell catching fire may be lower (due to lower amount of cells), due to the size of the cells, being in a pouch with no solid metal housing per cell, and how they are packed together, a single defective cell pretty much guarantees at least an entire module catches on fire, if not the whole pack.
Other factors that may come into play with LG's case specifically is the higher energy density and chemistry type (NMC). The Bolt had 60kWh with 288 cells or 208 Wh/cell, and the Kona Electric had 64kWh with 294 cells or 218 Wh/cell. The Volt had a similar cell design, but used LMO and only 16kWh from 288 cells, or 56 Wh/cell. The Leaf had 24 kWh LMO and 192 cells or 125 Wh/cell
The other factor may be LG's patented stack and fold design. This may introduce defects that happen only after the cell layers have been put into the pouch and would not be easy to catch with QC (would probably need X-raying each cell). Leaf used a more conventional stack design which probably is less susceptible to this kind of defect.
