Most people have never heard of an 8D battery. Its big and found mostly in boats, but is increasingly used in off grid power systems and RVs. There are a lot of battery sizes and it can be confusing to figure out what battery you need for your boat, RV, or off-grid power system. Many different brands, battery sizes, types, and features to choose from. One of the largest sizes of RV & marine batteries is the 8D battery, which is a big battery not to be confused with the Duracell D type cell battery that you would put in a flash light. An 8D battery is much bigger, about the size of a carry on suitcase. We're here to...