In simple terms, the number of banks refers to the number of separate battery groups that you can charge at the same time. If you have a smaller boat and only have one battery then you don’t have to worry about how many banks your charger has. The general rule is that you want to match the number of banks that your charger has with the number of battery banks that you have, whether that is one, two, three, or four. If you think you might expand your electronics then getting one more bank than you need at the moment will mean that you can be more prepared for the future.