These are the deep cycle solar batteries. They are normally used in solar cycling application where charging is done during the day and discharging at night regularly. In a typical application the discharge in 12-14hours a day and charging of about 5hours a day. This requires the batteries to have fast charge characteristics. The battery should be able to discharge deep enough (50%-80% DoD) without damaging the battery. A good solar should battery give service of above 1800 cycle.
Available sizes in 12V range as from 12Ah to 260Ah and 200Ah to 3000Ah for the 2V batteries.
The brands include Ritar, SHOTO, Northstar and Enersys.