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.
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:
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.
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?
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 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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
Do you need a diesel generator to go cruising? It’s a surprisingly simple decision governed by only two criteria.
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.
The story of how John nearly wasted a bunch of time and money, but finally got a grip of himself. Lots of electrical system recommendations and a caution to make sure that the complexity we choose is right for us.
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.
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.
Matt examines lithium ion batteries in detail and answers the question, “Should I use lithium ion batteries for the house bank on my boat?”
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.