- What Is An 8D Battery? Are They Worth It?Perhaps you’ve never even heard of an 8D battery. It can be overwhelming to pick out a deep cycle battery for your boat, RV, or off-grid system. There are lots of different brands, types, and sizes. One option you may come across is the 8D battery, not to be confused with D-cell for small electronics. […] The post What Is An 8D Battery? Are They Worth It? appeared first on Battle Born Batteries.