In the last two chapters we took a deep and considered dive into analyzing the electrical loads on our boats and thinking about ways to reduce said loads through smart systems thinking. Now we get to the payoff: How to calculate optimal battery bank size or, alternatively, how to live with the battery bank size we already have. I have built a spreadsheet to make the whole process easier. And I have updated my thinking on lithium batteries too.

Two core decisions we must make when designing a cruising boat electrical system for living aboard full time and making offshore voyages, are the size of the battery bank and which charging sources we will need: generator, solar, main engine, wind, etc.

But the first thing we need to do, before getting into all that fun stuff, is think about electrical consumption and how to keep it reasonable.

There are two opposing views on chain catenary: those who believe that having a lot of chain on the bottom increases holding, and those who have observed an all chain rode being pulled bar straight in any winds above about 30 knots and therefore hold that catenary does nothing useful in anchoring. Who is right? Read on to find out, and also for John’s recommendation for the best chain grade to use.

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