More on the "will batteries have enough power to maintain propulsion..." In short, no.
Reading the info on the Lagoon 440, it seems that the electricity for propulsion will be provided by a generator - pretty much as is done on US Coast Guard Ice Breakers. The batteries can drive the boat for a short time without the generator, but certainly not for long periods. Alternate electric generation, with solar panels and wind generators, would probably decrease the fuel consumption somewhat, but not entirely.
In the long run I guess you would consider the reliability of the generator in pretty much the same way as you might look at a diesel engine.
I posted some comments regarding a novice's purchase of an electric Lagoon 440, HERE
- I didn't really say it outright, but I felt that the man's inexperience was probably his greatest problem, and his inflammatory comments to me, which I didn't repeat here, struck me as anger at others which should possibly have been directed to himself instead. I think, though, that the huge weight of the batteries on the Lagoon has to negatively affect the performance of the catamaran, and as enamored as I thought I was about electric engines, I think there's still a lot to do before they are a viable alternative to the diesel engine. Better to have a boat that sails well rather than rely totally on engines - my take, anyway.