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Comment by alex7734 | Hacker News Reader

> it could release highly toxic hydrogen sulfide gas.

How bad is it in real world conditions? Because from what I'm reading it's not the "it makes you sick" kind of toxic, but rather the "it kills you in seconds" kind of toxic.

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There’s no way to concentrate energy without creating some danger. Gasoline is quite dangerous but we drive around with tanks full of it now. Natural gas and high-amp electricity are dangerous but we have them coming into many houses.

So I would propose the question shouldn’t necessarily be, “how bad is the worst-case scenario”—it’s pretty bad for all energy sources. I think a better question is “how reliably and efficiently can we prevent or mitigate the dangers.” That will go a long way toward determining its commercial viability.

Current lead acid batteries can do this as well. Smells awful and pretty unsafe situation. H2S is quite dangerous but it’s rare that they’d create an IDLH situation as long as there’s a bit of breeze.

i'd be surprised if lead-acid batteries produce detectable quantities of hydrogen sulfide; isn't their sulfur bound up in an extremely stable oxoanion? still, https://web.archive.org/web/20161005164308/http://www.wesh.c... certainly doesn't sound like sulfuric acid

I've discovered damaged lead acid batteries in equipment by following the rotten egg smell back to it's source. Twice, both small current 12V DC batteries.

Humans are _very_ sensitive to the smell of H2S. Unless you meant that it might produce enough to kill your sense of smell, which is possible.

no, i meant i don't understand how you get from sulfate to prussiate at room temperature

Yes this was my initial reaction: what if a tesla battery comes in contact with water? What degree of "more dangerous" are we talking about?

MSDS for H2S - https://www.airgas.com/msds/001029.pdf

The Occupational Exposure limits are fairly low 'ppm' numbers, and LC50 is 712ppm for 1 hour. (That is the concentration at which 50% of the exposed rats died.)

Someone else pointed out LD50 is ~700ppm

It's unlikely you'd be exposed to this level for any period of time unless the battery ruptured into the car, underwater, with the windows up, in which case you have bigger problems. You're unlikely to to see 700ppm in an outdoor situation like a car wreck or battery malfunction on the highway during a rainstorm. Atmospheric CO2 is about 450ppm for comparison.

Ammonia is a superior refrigerant (widely used in industrial circles, and causes no ozone depletion, is biodegradable, etc) but not used in residential applications because it's highly toxic if there's a catastrophic seal failure and not vented outside, despite the fact that humans are very efficient at smelling even the slightest ammonia leak.

I think H2S is somewhat bigger of a safety risk than presented here.

For example, check out this case where what you describe (battery rupture) happened, killing both occupants from H2S inhalation:

https://web.archive.org/web/20161005164308/http://www.wesh.c...

And this was only from a starter battery, not a battery sized for vehicle locomotion.

It's interesting that Porsche put the battery under the driver's seat (in the cabin? unclear). Wonder if that made it more dangerous. Are modern EV batteries also in the passenger area or in their own little armored section...?

It was probably put there for weight distribution as Porsche would be more likely to optimize for that despite the user inconvenience it may cause

Possibly for a Carrera, but for a Cayenne? Despite the Porsche brand, that isn’t anywhere close to a sports car. The platform is shared with the Audi Q7 and the VW Touareg. It’s a tractor with nicer seats. The weight of a battery fitting under a driver seat would be similar to a big shopping run, so weight distribution wouldn’t have been a consideration.

Manufacturing logistics probably played a bigger role.

My Land Rover Defender had the battery under the seat as well.

But hey, there are so many holes in the car it’s basically permanently venting…

As excited as I am, there are some kinks in the supply chain that may need some extra taking care of [1]. Although this incident involved relatively few electric vehicles on open sea, it would be even more difficult to contain with larger shipments. Modular battery installations and separate fireproof(ed) shipping are options that need to be considered.

[1]: https://apnews.com/article/cargo-ship-fire-netherlands-envir...

Cars are often in tunnels, could be dangerous there?

For comparison purposes, note that indoors CO2 will go from 400 -> 1000ppm+ rather quickly if its not ventilated

According to this source [1], CO2 went from 400 -> 3000ppm inside a car cabin in 30mins, which is ~86ppm/min just from breathing. I could easily imagine a gas inside a car leaking at a faster rate and reaching 700ppm in a very short period of time.

[1]: https://www.co2meter.com/blogs/news/high-carbon-dioxide-co2-...

HS is funny stuff. Does nothing then zap, ur dead.

UK figures for safe working concentration in air, from memory, hydrogen cyanide 11ppm, hydrogen sulphide 10ppm

I remember synthesizing H2S in high school (for chemistry practicals, I think). I made the mistake of attempting to smell it. This was for a fraction of a second—but during that time, I could feel the individual bubbles of gas entering my nose; and I almost passed out.

Rotten eggs smell is just about everything you can get from this kind of experiment.

Now if they scale it up. but at any scale that makes sense economically you can get suffocated by just about any gas you can think of. Like helium or hydrogen.

H2S is also a byproduct of crude oil processing. The nose is easily overwhelmed by the smell even at low concentrations, and it becomes hard to notice before it strikes.

Depending on concentrations required for consequences a smelly gas is much safer than something like CO

I believe you go noseblind to hydrogen sulfide very quickly. [1]

[1] https://dodtec.com/news/the-potential-dangers-of-hydrogen-su...

Perhaps "safer than CO" is fair, but "much safer than CO" may be a bit of a stretch. H2S is the #2 cause of fatal chemical inhalations in the workplace, behind CO:

https://www.bls.gov/opub/ted/2019/fatal-chemical-inhalations...

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