No trying to discourage anyone from scrounging parts, but sometimes being able to order what you need is the way to go. There's a lot of battery options availble thru automotive performance catalogs, including 16v batteries, chargers, step down transformers, isolation switches, sealed battery boxes and battery relocation kits and charging lugs. Check out the battery disconect switch for $16, every dragrace car with a relocated battery is required to have one, so the cost has come down. These catalogs are a good place to steal ideas to suit your own ecomodder or other needs. As someone else mentioned, West Marie is a great source of all-weather 12v electrical items, I've used many of their electrical products on race cars and trailers, very superior reliability compared to the absolute junk sold at the chain auto parts stores.
Powermaster 16V Battery Accessories - JEGS
and
Powermaster XS Power Batteries - JEGS