alt Hacker NewsA quick googling suggests that unloading such a vessel takes at least a couple of days, more likely 3-4.
Assuming two days available to charge the vessel, you'd need about 100MW continuous. Not trivial, but doable.
As far as battery fires go, sure, but a) there are already a lot of electric ferries in service so designing safe maritime battery packs isn't a new challenge and b) the alternative isn't exactly risk free either; we've seen plenty of oil spills from ships.
The fire thing comes up with cars all the time. Petrol cars are vastly more likely to catch fire, but are a bit easier to extinguish.
I can only imaging how hard it is to put out a ship fire, but is there any reason to see that the situation would be different? Bunker fuel appears to be less flammable.