Online Book:

Cruising Boat Electrical Systems

Here’s how to get the very best from a cruising boat electrical system—real information that works based on 25 years of live-aboard experience on boats with batteries. John is an electronics technician by trade, so qualified to provide practical and reliable information for both sailors and power boaters.

Table of Contents:

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.

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.

How Batteries Get Wrecked and What To Do About It

So far in this Online Book we have covered the basic theory. Now let’s look at, and quantify, what will happen if we just stick with the electrical system installed on most boats. After all, if we are going to improve things, it’s as well to know what the payoff will be.

11 Steps To Better Battery Life

In the last chapter, we quantified how short battery life will be on a cruising boat with a standard electrical system, now let’s move on to fixing that.

10 Tips To Buy And Install A Live-aboard’s Alternator

On a cruising sailboat the batteries will likely be charged most often by an alternator on the main engine, particularly if the boat does not have a generator. And if you live aboard, the alternator that came with the engine is simply not going to cut it. In this chapter we share how to buy and install a real cruiser’s alternator.

Installing And Programming The Right Alternator Regulator

Even if you have the biggest and best alternator in the world, if you don’t have a good regulator and, in most cases, reprogram it from the factory default settings, your batteries are not going to get the full charge they so desperately need. In this chapter we share how to buy and reprogram a regulator.

Smart Chargers Are Not That Smart

Most marine battery chargers are, in fact, battery killers. Yes, that includes most of the fancy three stage units we all pay so much money for. Here’s why and what to do about it.

Equalizing Batteries, The Reality

Fully charging your batteries after each discharge on a live-aboard cruising sailboat is simply not practical. Instead, most of us will cycle our batteries between 50 and 80% of their capacity. The bad news is that this will ruin your lead-acid batteries (regardless of type) in a distressingly short time due to sulphation. However, there is a solution: equalization. In this chapter we cover what it is and how to do it.

Battery Monitors, Part 1—Which Type Is Right For You?

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.

Battery Monitors, Part 2—Recommended Unit

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.

Battery Bank Size and Generator Run Time, A Case Study

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.

Battery Options, Part 1—Lithium

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.

Battery Options, Part 2—Lead Acid

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.

Q&A—Are Battery Desulphators a Good Idea?

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.