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> You seem to be under the common misconception that it's the energy density of batteries that make them unsafe. not at all. in fact, i said their (comparative

> You seem to be under the common misconception that it's the energy density of batteries that make them unsafe. not at all. in fact, i said their (comparatively) low energy density is what makes them safe. that low energy density is a problem for range, places a lower bound on the size of vehicle, and somehow fixing that issue will make battery storage a far less safe option. > There's nothing inherent about battery energy density that makes them more dangerous. yes, their absolutely is - gasoline requires air to burn. batteries store energy, and they can discharge that energy without any other materials: a battery could burn in space. > What makes LiPo/Li-ion unsafe is that they have a flammable liquid electrolyte in the middle. well its the combination of the electrolyte and the metals that make the battery the battery, it wouldn't be battery without it. > EVs, even with LiPo/Li-ion, are FAR safer than ICE vehicles, there's just no competition. indeed, and i don't disagree. i think you may have misunderstood what i was trying to say about about safety here: i'm not trying to suggest that gasoline vehicles are inherently safer, at all. i'm saying that if you were to create a battery technology that was even 10x more energy dense, i.e. 10MJ/kg, you'd have great difficulty in making that vehicle safe. > But the fire department here in Norway say they already have the needed training/experience, and make it clear that EVs are far better for fire safety in general. once the battery has started burning, it has basically inextinguishable. "clear the area" is the only option you'd have. > As for your points on whether they're better for longer distance, personal journeys.. I mean, yeah.. at some point they are. If you're driving 1000km in a day I'd definitely agree. But how many people do that often? in Europe? probably not much. in the US? India? Pakistan? > [...] For most people the range of EVs is good enough, even for long trips. likely true, and, as i mentioned, EVs have a place. > Almost every single road-trip charging session for me has been: 1. spend 30 seconds plugging in and beeping the payment card (with Tesla you don't even have to do this). 2. walk into a restaurant/cafe/grocery store and take a pee, drink some coffee, buy groceries for the trip, etc.. 3. come back to a fully charged car well there's a couple of issues there - adding 30/45 minutes to a journey like that might not be suitable for everyone. traumatic charge rates (above 4C) are not good for the battery, too. > The only reason you need that expertise with ICE drivetrain is because it's so hard to maintain. well even the linked video states that this isn't really the case these days for ICE vehicles, a point i largely agree with. regardless, if gasoline could be recovered from the atmosphere - closing the CO2 cycle - what would be so bad about this? as it stands, with EVs alone, we're pushing the costs of a complete infrastructure change over to individuals. sure, government assistance might help us here in the west, but that's not the world a lot of people live in.

bryanlarsen 4y ago
To make a battery safer, you reduce the ways it can give up that energy. For example, some batteries will give up their energy if they are penetrated with a sharp object. Some won't. Some tolerate high temperatures, some don't. Energy density is only loosely correlated with safety.
- foxhill 4y ago
  > To make a battery safer, you reduce the ways it can give up that energy. well, not exactly: > [...] some batteries will give up their energy if they are penetrated with a sharp object. Some won't. and your options for surviving punctures are essentially either: * make the battery store less energy, or * don't stack/roll the battery layers. the first is clearly a non-starter, the latter necessitates very flat & space wasting batteries. > [...] Some tolerate high temperatures, some don't. lithium based batteries chemistries are completely unfavorable to high temperatures. there is no way around this, without changing the chemistry of battery (which is likely an energy density decrease), or adding thermal mass to soak up extra heat for some finite duration. > Energy density is only loosely correlated with safety. ok, consider this scenario: say we found a battery chemistry is resilient to puncture. can tolerate hundreds of degrees of heat without issue, and can sustain the power required to drive an electric car. ultimately you have 50kwh battery with a positive and negative terminal. you could put a bar of copper over those terminals. one of two things is going to happen; * the copper will rapidly heat up and explode * the battery will rapidly heat up and its container will explode this battery is still very dangerous.
  - bryanlarsen 4y ago
    proof by example: https://youtu.be/CGQwqWqzkNA https://youtu.be/CGQwqWqzkNA We do agree on one thing: significantly safer batteries have to use a different chemistry than Lithium NMC.
    - foxhill 4y ago
      it looks like that battery is exactly what i'd said it'd be: a flat, less space efficient form factor. all you're seeing here is fewer layer penetration from the puncture, and more surface area to dissipate the heat over. note, you can't stack these on top of each other (without loss of safety), otherwise you have a conventional battery again, this time with more conductors in between each cell.

bryanlarsen 4y ago

To make a battery safer, you reduce the ways it can give up that energy. For example, some batteries will give up their energy if they are penetrated with a sharp object. Some won't. Some tolerate high temperatures, some don't. Energy density is only loosely correlated with safety.

foxhill 4y ago
> To make a battery safer, you reduce the ways it can give up that energy. well, not exactly: > [...] some batteries will give up their energy if they are penetrated with a sharp object. Some won't. and your options for surviving punctures are essentially either: * make the battery store less energy, or * don't stack/roll the battery layers. the first is clearly a non-starter, the latter necessitates very flat & space wasting batteries. > [...] Some tolerate high temperatures, some don't. lithium based batteries chemistries are completely unfavorable to high temperatures. there is no way around this, without changing the chemistry of battery (which is likely an energy density decrease), or adding thermal mass to soak up extra heat for some finite duration. > Energy density is only loosely correlated with safety. ok, consider this scenario: say we found a battery chemistry is resilient to puncture. can tolerate hundreds of degrees of heat without issue, and can sustain the power required to drive an electric car. ultimately you have 50kwh battery with a positive and negative terminal. you could put a bar of copper over those terminals. one of two things is going to happen; * the copper will rapidly heat up and explode * the battery will rapidly heat up and its container will explode this battery is still very dangerous.
- bryanlarsen 4y ago
  proof by example: https://youtu.be/CGQwqWqzkNA https://youtu.be/CGQwqWqzkNA We do agree on one thing: significantly safer batteries have to use a different chemistry than Lithium NMC.
  - foxhill 4y ago
    it looks like that battery is exactly what i'd said it'd be: a flat, less space efficient form factor. all you're seeing here is fewer layer penetration from the puncture, and more surface area to dissipate the heat over. note, you can't stack these on top of each other (without loss of safety), otherwise you have a conventional battery again, this time with more conductors in between each cell.