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Online Book Table of Contents:

Electrical Systems For Cruising Boats


How to get the very best from a cruising boat electrical system—real information that works based on 25 years of live-aboard experience. John is also an electronics technician by trade, so doubly qualified to provide practical and reliable information.

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.

These days we are seeing more and more gear added to boats, much of it AC supplied through inverters from the battery, that demands currents (amperage) way higher than even dreamed of a decade ago. But will our electrical system buckle under the load? Here’s how to figure that out ahead of time.

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.

Stupid Alternator Regulators Get Smarter…Finally

One of the biggest snow jobs in boat gear sales is the myth of the smart three-stage alternator regulator. In fact, the alternator regulators that have been available to us cruisers for about the last 15 years are not that bright…OK, they’re downright stupid. But, finally, we now have a truly smart regulator. John takes a look and comes away impressed.

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.

Renewable Power

Through a combination of planning, frugality, solar and wind power, Colin and Lou have never had to run the engine of their OVNI 435 to charge their batteries when at anchor. How did they manage that? Read on to find out how.

Wind Generators

Should you install a wind generator on your boat? Find out from someone who has cruised with one for 5 years—invaluable real-world experience.

Solar Power

There are very few cruising boats these days that don’t have a solar panel fitted somewhere, and many have some pretty substantial arrays. Based on five years of real-world experience, Colin gives some tips and recommendations for how to get the maximum benefit from solar.

Hydro Power

Meeting daily electricity needs using power and solar while at anchor is one thing, but what about when passagemaking? Solar can only do so much and wind generation works best when sailing to windward. So is hydro the answer? Colin talks about the pros and cons of hydro generation.