Should I hook up batteries in Parallel or keep them in separate banks? There are advantages and disadvantages to both options,
- The advantage of having batteries in parallel of course is that it makes a larger battery bank which will be less discharged in percentage terms and so will have a longer life. It will also make a simpler electrical system, less switches, combiners, isolators, expense and potential operator errors. So in reality everybody has batteries in parallel and just has to deal with the consequences.
- The main disadvantage as I see it is that as the batteries get old one will fail first, quite often by getting a shorted cell. It will very quickly damage the other batteries by causing them to be overcharged. When not charging the good batteries get worn out trying to charge the shorted battery. The end result is the entire bank quickly fails. One way to guard against this is to use an Amp Hour meter and measure the calculated efficiency of the batteries from time to time. Any drop in the level could indicate a bad battery. I have found from experience that at an efficiency reading of 85% that the batteries are still working but on their way out. Replacing batteries at an 85% efficiency rate is a good way of avoid unpleasant breakdowns out on the water