Online Book: Electrical Systems For Cruising Boats

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.

In the last chapter we looked at some big loads that take electricity from our battery. In this chapter John covers watermakers and diesel furnaces and shows how system thinking can save us from having to install a silly-sized battery bank.

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.

The single biggest bitch we hear about battery monitors is that they are always wrong. John shares how to fix that and make your batteries last a lot longer too.

Being able to accurately monitor our batteries is a vital function for all cruisers, but which of the multitude of systems offered should we buy and install? John defines the functions we actually need, and then recommends a monitor.

It’s tempting, when selecting a complex piece of gear like a battery monitor, to dive straight into the details and features, but that’s a near-sure route to a bad decision. First let’s take a giant step back and look at the two main types of monitors and decide which is right for each of us.

These days, most boats with AC generators have significant DC (12- or 24-volt) battery banks that need to be charged regularly by the generator. But often that process is horribly inefficient. The good news is that the fix is easy, simple, and relatively inexpensive.

John takes an in-depth look at the benefits and drawbacks of carbon foam, liquid filled, and AGM lead acid batteries, and then reveals his thinking if faced with battery replacement today.

John recently replaced the house battery bank on Morgan’s Cloud. But before starting the project he had a big decision to make: which battery type. Here’s a look at the options he considered, starting with lithium.

Are you considering a hydro generator? Here’s everything you need to know, warts and all, from an experienced user.

The claims made for battery pulse desulphators seem to make them ideal for voyaging boats. A cheap, easy to install gadget that will dramatically extend your expensive batteries’ lives. What’s not to like? But do they really work? John takes a look.

Charging batteries fast has all kinds of benefits: less engine wear, fuel savings, less carbon. But how far can we go and what are the lurking dangers?

The details of how batteries charge and how voltage regulators work together…or not. Practical information that will help make sure you have electricity when you need it.

Electricity, batteries and how to charge them are the source of more confusion in the cruising world than just about anything I can think of. But suppose you could really understand electricity? Now you can, and it’s not hard. Read on.