Things that will destroy a boat battery
The site On the Lake has an entire section on boat batteries from which we extract some knowledge about potential damage for the battery of your boat or yacht.
Have you ever had a battery that seems to work well but "dies" much more quickly than expected? The problem may be a battery that is heavily sulfated, often the result of only light use (being discharged by only 15% or so). The sulfuric acid has become concentrated on the batterys bottom and sulfate crystals have begun to form.
(Nowadays) there is an incredible variety of batteries that are available for every imaginable use: marine starting & trolling, auto, agricultural, industrial. They all have at least one thing in common: they need to be maintained to some degree, even the "maintenance free" types.They will lose their electrolyte during normal use and need to be checked; all need to be recharged.
(...) Be very careful when recharging them; "smart charger" technology is required or damage can easily result. They are also more expensive but do have their advantages. The most important thing for the flooded acid variety is to keep them full. Top them off with distilled water only whenever possible, as minerals in tap water can contaminate the electrolyte. Keep the terminal clamps clean and free of corrosion; coat them with anti-corrosion spray or even petroleum jelly. Check connections and keep them tight; watch for frayed wires and replace them. And for a few bucks spent at your local auto parts store, a Battery Hydrometer, used to check the specific gravity (concentration of acid) is a good investment. It is a great way to determine if one of the cells is bad. If the difference in specific gravity is 30 points or more, it is time to replace your battery!
En Nationwide Batteries: