When wiring a bank for series / parallel you will first want to fit and orient the batteries as they will be physically installed on the boat. You then construct the series jumpers and wire them.


Once you've created your series 12V banks you can then wire them in parallel. As explained above, by EnerSys/Odyssey Battery, it is important that the loads and all charging input be wired from opposite ends or corners of the bank, as shown, to help keep it in balance throughout its life.


With a series parallel set up the ONLY TERMINALS you connect the boat to are those two corners. You do not want to "center tap" with a 6V series or series/parallel bank otherwise you may not have a 12V bank for that circuit..



Final Thoughts:


Can 12V Group 24, 27, 31, 4D & 8D flooded batteries work? Sure, absolutely, and they do in the tens of thousands on boats every day.


The question here is of value and are you getting what you paid for on the sticker, or were sold, when you bought what you thought was a deep cycle battery? When a 12V flooded marine battery is sold for more money and with half the rated lab cycles my answer = no.


When purchasing house bank deep cycling batteries always consider cycle life in the equation. This is the part most everyone buying batteries forgets or entirely leaves out of the decision making process. The battery buying process is not just about Amp Hours and $$$. It is Ah's, $$$ and cycle life when you are buying deep cycle batteries.


By labeling "light cycling" batteries as deep cycle it's the battery maker who wins because you'll buy more batteries in a shorter period of time. By doing your home work you can avoid getting bitten by the muddy and misleading marketing of light cycling batteries.