Oils4AsphaultOnly said:
For the Tesla novices, a model S/X battery module is a brick unit composed of over 400+ cells. There are plenty of teardown videos showing that every battery pack is made from 12 to 16 of these modules.
Having a module fail doesn't tell us anything about whether having the cell protection circuitries would've done anything to help. Much like how the iPhones, Samsung Galaxy phones, and the Boeing 787's all had cell overcharge/discharge circuits in place, yet didn't prevent them from going into thermal runaway.
Correct me if I'm wrong, but ISTR that those all involved LiCoO2 cells. I'm pretty certain the battery cargo fire that caused the crash of UPS Flight 6 involved LiCoO2 batteries, and led to restrictions on
all Li-Ion battery shipments by air, e.g.
2019 Lithium Battery Guidance
Document, Revision 1
Transport of Lithium Metal and
Lithium Ion Batteries
https://www.iata.org/whatwedo/cargo/dgr/Documents/lithium-battery-shipping-guidelines.pdf
DOT Issues New Rule for Air Transport of Lithium Batteries
https://www.lexology.com/library/detail.aspx?g=dd81f41b-8e3e-4e6c-9a20-5932a12ee4e7
Battery University
https://batteryuniversity.com/learn/article/types_of_lithium_ion says of both LiCoO2 (Roadster) and LiNCA (Model S et. seq.):
Thermal runaway 150°C (302°F) typical, High charge [Full charge for LiCoO2] promotes thermal runaway
LiNMC, which everyone else seems to be using now except maybe some Chinese companies, is safer:
Thermal runaway 210°C (410°F) typical. High charge promotes thermal runaway
The LEAF originally used LiMn2O4, which is safer yet:
Thermal runaway 250°C (482°F) typical. High charge promotes thermal runaway
Finally, LiFePO4, which AFAIA no one except maybe some Chinese companies is using now (the MY 2013 Spark had them), is the safest of all (except LTO used only in the Fit EV), albeit having the lowest specific energy (NCA is the highest):
Thermal runaway 270°C (518°F) Very safe battery even if fully charged
So, Tesla presumably decided to use the batteries with the highest specific energy and energy density, but also the highest chance of thermal runaway, because they needed to set themselves apart from the rest of the manufacturers, as BEVs are their whole business. The mainstream car manufacturers had no need to take such risks, because their profits aren't tied to BEVs which are a small niche for them, and they have no desire to risk liability for the company by accepting the higher chance of thermal runaway. Both of those decisions make sense.