Lithium, page-1693

Also a lot of the larger sailing yachts up to 35m/110 ft have late battery banks built in allowing the generator to be shut down while maintaining normal operations underway. I've replaced a couple of banks of less acids at 24* 2v cells @ 112kg each so lithium will be a big winner for yachts.
There was a new "J" class launched last year, s/y Topaz that is a diesel electric hybrid with an amazing custom propulsion system using lithium batteries it can popel using thebattery driven electric motor so the whole boat can run silently under motor when the wind is no good.
This is the yard that built it and there is a PDF doc if you click on the image that explains a bit more in depth the hybrid system used.
http://www.hollandjachtbouw.nl/innovations/hybrid-power-sy/