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Cake day: August 24th, 2023

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  • My bet is they were just told it was a fire, i doubt the person to drive by and report it would have known it was an electric truck.

    The batteries definitely do have fire protections, to help delay the spread. Dousing it with 50k gals of water may have prevented the spread to another compartment for all we know. For something as big and higher risk like a semi though maybe there’s a way to eject compartments. Like if a fire starts in Module 1 of 4, modules 2 to 4 can eject themselves further away. Then were only dealing with a 250kwh fire instead of a 1mwh fire. It would add weight though.

    Edit: And then while the firefighters keep the flames at bay, something could get attached to the other compartments and be dragged further away.



  • The batteries (a battery is a bunch of cells) actually are made to be resistant. Be it firewalls between the cells, fuses, fire retardant, exhaust systems, BMS for thermal management etc.

    The cells it’s just the nature of the chemistry and form.

    The pouch cells used in many EVs are actually more fire prone than the cells used in a Tesla or Rivian. They are very easy to puncture, so in an accident or from manufacturing defects their fire risks are higher. They’re also larger in format and each cell contains more energy, resulting in a risk of more fire if something goes bad.

    Prismatic and cylindrical cells are less fire prone and IMO should be the only choices. I wouldn’t be surprised if pouch cells were deemed unfit for vehicles far in the future, but probably not before the industry moves away from them naturally. Many have already announced moving away from pouch cells. One of the reasons they’re used in cars today is there was excess pouch manufacturing capacity compared to prismatic/cylindrical. The existing OEMs had to cobble together a battery supply chain with very few options.

    Then the chemistry is important too. Lithium iron phosphate cells are more tolerant and less likely to have thermal runaway than the NCA or NMC (nickle coblat aluminum / nickle manganese cobalt), but their power density is lower, so you aren’t making long range vehicles (or semis with good range) today. LiPo cells are prismatic as well due to the nature of how they are made, so less fire risk from chemistry, and less risk from battery cell form.

    Sodium Ion are even less likely, but it’ll be well over a decade before you make more than a commuter car with those, if ever. Toss them in a cheap to build car though and we can make a really great and cheap commuter vehicle in the near future.

    Edit: more details.



  • I don’t even think this is the right metric to use.

    You aren’t putting a lithium battery fire out with water. You’re just keeping it at bay until the energy is all used up. The more energy, the longer it’ll take.

    We might need new ways to deal with these fires, but it’s not like we can completely submerge a semi in water.

    I wonder how encasing the object in a fire retardant foam would behave, although we gotta think about the toxicity of that too.

    Edit: I wonder if you could even calculate the amount of water you’d need to hold it off upfront based off the battery size and current charge.