Probably not very many because the fuel supply is transported separately from the vehicle. Which is probably what we should be doing with electric cars. Transport the hazardous component (batteries) on a separate ship to reduce the damage when incidents happen.
A comparable question might be "how often do oil tankers catch on fire?". I don't know the answer, but there have been at least two this year:
You fill both ships. There's not much loss in efficiency, just separating hazardous material. Maybe you should look up how many ships full of oil it takes to power all of the gasoline powered cars. It's a lot.
How many of those "conventional" vehicle fires happen on container ships during transport?
Probably not very many because the fuel supply is transported separately from the vehicle. Which is probably what we should be doing with electric cars. Transport the hazardous component (batteries) on a separate ship to reduce the damage when incidents happen.
A comparable question might be "how often do oil tankers catch on fire?". I don't know the answer, but there have been at least two this year:
January: https://www.youtube.com/watch?v=I34ESUp6mdI
May: https://www.cnn.com/2023/05/01/asia/malaysia-coast-oil-tanker-fire-rescue-intl-hnk/index.html
You fill both ships. There's not much loss in efficiency, just separating hazardous material. Maybe you should look up how many ships full of oil it takes to power all of the gasoline powered cars. It's a lot.