Bridge Rectifiers | Mouser
http://www.mouser.com/search/Product...R=833-MP506-BP
These guys are showing 25 amp, 200v bridge rectifiers with a 1.1v drop... at least I think I'm looking at the specs right, either way you would want a heat sink on it as well, maybe a small fan as well.
I would look more at the open source chargers and see if the design could be tweaked to work with a 48v DC input.