Batteries with Prussian blue cannot kill people silently.

Cyanide could be released only at high temperatures, e.g. if the battery is opened and burned, not during normal operation, even if overcharging is not prevented, as it should.

The sulfuric acid from the traditional lead-acid car batteries is more dangerous than this.

We pipe methane into millions of homes. I don't think "this can silently kill people in the worst case" is enough to block something.

We also have to adulterate that methane with bitter smelling agents too warn people of the danger when there's a leak. The line into the house is also limited by a regulator to ensure the pressure is very low. If gas builds up in a battery, it's either going to leak out slowly or build up and leak out all at once.

Very much not an equal comparison.

What the other poster said about the risk of releasing cyanide during overcharging is not true.

Cyanide could be released only at high temperatures over 300 Celsius degrees.

During a fire, there are many other things in a car that can release toxic fumes easier than a sealed battery.

The methane is almost always piped in to be burned, and that can easily create odorless carbon monoxide. And the smell is not foolproof either. This does routinely kill people and we keep doing it. The jurisdictions that are banning it are doing so because of environmental reasons, not safety.

> hydrogen sulfide is not anywhere in the same category.

It has the same LD50 dose as HCN. It literally _is_ just as bad. It routinely kills people on oil rigs because in lethal concentrations it immediately shuts off your nose.

How often do you hear about people getting poisoned by it from lead-acid batteries?

Not precisely the same:

https://en.wikipedia.org/wiki/Hydrogen_cyanide - 107 ppm (human, 10 min)

https://en.wikipedia.org/wiki/Hydrogen_sulfide - 600 ppm (human, 30 min)

https://en.wikipedia.org/wiki/Carbon_monoxide - 4000 ppm (human, 30 min)

These are "LCLo" values from the databoxes on those pages. More easily comparable numbers may be around somewhere.

Hydrogen cyanide has the bonus of being mostly odorless too. Whereas hydrogen sulfide is distinctly bad smelling.

Apparently it only smells bad if you have non-lethal concentration.

The only people with any significant amount of lead acid batteries on their property are off grid types who typically store them away from their primary domicile as a fire safety precaution.

Fast charging a car/chemical weapon in your garage isn't terribly appealing.

If that battery is a chemical weapon then so is a big half-plastic box with ten gallons of gasoline inside.