Well written and illustrated explanation of how batteries are built, how they are wired, and how you should dispose of used batteries.
A couple who have completed at 10,000-mile tour of the Pacific on a 31-foot cutter talk about what equipment they chose and how it worked, including their battery capacity and management.
An argument against placing your boat's batteries in parallel, the normal configuration, for safety and efficiency reasons. Instead the author favors two separate battery banks operated alternately and charged separately.
Range of sailboat electrical gear including battery switches, panels, voltage-sensitive relays, switches, terminal links, fuse holders, circuit breaker panels, and other electrical control devices.
Unmoderated forum on marine electrical and electronic equipment, including batteries. Good advice and resources here, but you have to dig and you have to be selective.