Boat Electrics

Boat Electrics 101 - Safe & Reliable DC Systems

8 Modules 56 Lessons Beginner

About this course

In this course you will learn everything you need to know about DC systems on boats. Beginning with the basics about current, voltage and resistance, we teach you how to (re-)do all DC wiring on your boat, complying to ISO and ABYC standards.

Course Structure

3 Lessons


About Boat Electrics 101

A quick welcome and introduction of your teachers and a few words on who this course is for and what to expect.

Course Structure & Overview

Get an overview on the contents of this course and the underlying standards.

Safety Precautions

In this lesson we will cover some dangers and necessary safety precautions to keep in mind before working on your system.

Premium Course
5 Lessons


Get to know the basics of electricity and learn about Volts, Amps, Ohms and how they relate to each other.

What is electricity?

What is electricity and what happens when a current flows? We take a quick look at the behavior of electrons inside metallic conductors.

Voltage, Current & Resistance

Learn all you need to know about voltage, the equivalent to pressure in electrical systems.

Ohm’s Law

Ohm's law allows you to calculate how resistance affects voltage given a certain current and vice versa.

Power, Energy, Consumption & Capacity

Power the product of voltage and current. With two examples you will learn how to calculate the power draw of an appliance.


A quick recap on everything we have learned so far.

Premium Course
9 Lessons

Electrical Components and Circuit diagrams

Get to know the most common components of a boat's electrical system and learn how they can be represented in a circuit diagram.

The Idea Behind a Circuit Diagram

Learn why it is important to be able to read and draw circuit diagrams.

Wires & Conductors

In this lesson you learn the symbols for wires and wire connections.

Circuit Ground

What is ground/earth and how is it represented in circuit diagrams?

Switches, Buttons & Relays

Get to know the basic symbols for switches and buttons and learn how relays and solenoids work.

Resistors & Shunts

Get to know the symbols for resistors and learn about the most common type of resistor on board: the shunt.

Fuses & Circuit Breakers

How are fuses and circuit breakers represented in circuit diagrams?

Coils & Transformers

Coils mostly occur on boats within transformers. Here you will learn about their basic function and how to represent them.

Lamps, LEDs, Diodes, etc.

In this lesson you will get to know a few more symbols for common components in a boat's electrical system.

Basic Circuits

In the final lesson of the module, you will learn how the components in boat electrics are connected in parallel and in series and how this affects battery capacity and voltage.

Premium Course
9 Lessons

Cable Selection and Installation

In this module, you will learn how to choose the right type and size of cable and how to properly install it. This is crucial knowledge for anyone planning any modification on their boat's electrical system.

Cable Construction

Learn about different types of cables and which ones are suitable for use on boats.

Colors & Labeling

Learn what cable colors you can use for what purpose and how to properly label your wiring.

Sizing Cables

Learn how to choose the proper size for a cable with respect to ampacity and voltage drop.

Terminals & Terminal Installation

It is crucial for the system's safety to establish proper connections. In this lesson you will learn how to install terminals in a professional manner.

Making the Connection

Proper connections of terminals to bus bars and consumers are vital. Here you learn what makes a professional connection.

Overcurrent Protection (OCP)

In order to prevent fires due to overcurrents and short circuits, protective measures are absolutely crucial. In this lesson you will learn how to choose fuses and circuit breakers and where to install them.

Cable Installation

Learn the proper way to install cables in order to protect them from chafing and physical stress

Case Study: High Output Alternators

In this lesson we will apply what we have learned in this module to the special case of high output alternators. As we will see, there are quite a lot of things to consider.

Bonus: Nigel’s Examples

Here we show a few more examples of good or bad installations and also what happens in case of a short circuit if no adequate OCP is installed.

Premium Course
11 Lessons


In this module we cover all you need to know about lead acid batteries.


Get an overview on what to expect in this important module.

Battery Safety

Even though they operate at relatively low voltages, there are significant dangers when dealing with batteries. In this lesson we cover the required safety measures.

Lead-Acid Battery Chemistry

In this lesson you will get an overview on the chemistry inside a battery and how lead acid batteries work.

Battery Construction

Here we go more into the details of the internal construction and discuss the differences between cranking and deep cycle batteries.

Battery Types

Now it's time to look at different types of lead acid batteries, such as wet cell, AGM, gel-cell and some new innovations.

Battery Efficiency

Learn about the crucial difference between amp-hour and watt-hour efficiency and how to evaluate batteries based on this.

Battery Ratings

What do the common ratings found batteries (nominal voltage, nominal capacity and cold cranking amp) mean?

Battery Failure Modes

In this lesson you will learn what the most common reasons for battery failure or reduced lifespan are and how to avoid them.

Series & Parallel Batteries

Learn how to maximize battery life when installing batteries in serial or parallel.

Sizing Battery Banks

This lesson will help you decide how much battery capacity you really need for reliable operation and optimal battery lifespan.

Lead-Acid Battery Installation and Maintenance

Learn how to properly install your battery bank and how to maintain it in order to optimize its performance.

Premium Course
8 Lessons

Charging Systems

In this module we cover in detail all you need to know about charging batteries. Topics include charging profiles, charging systems, charging circuits and systems monitoring.

Failure Modes Revisited & Expanded

Learn about the most common failure modes with lead acid batteries so mistakes can be avoided.

The Water Tank Analogy

Through the analogy of a water tank with semi-permeable membranes we explain why it takes a long time to completely top off a lead acid battery.

Charge Profiles

Learn what an IUoU profile is and how the bulk, absorption and float phases increase battery life.

Fast Charge & State of Charge (SOC)

Learn strategies to reduce charging times and engine hours while at the same time increasing your battery's lifespan.

Charging Devices

Learn what to look for when choosing a battery charger, an alternator or when planning on installing renewable energy sources.

Charging Circuits

Learn about different ways to charge multiple battery banks from a single power source.

Systems Monitoring

Learn about the importance (and challenges) of proper battery monitoring.

Summary: Batteries & Charging

A quick recap on what we have learned so far in this module.

Premium Course
4 Lessons

Energy Systems Design

In this module we will draw on what we have learned about batteries and charging systems to design an energy system optimized for how we want to use our boat

Energy Systems Introduction

In this lesson we introduce the BoatHowTo Boat Electrics Planner which will help us to determine the energy balance on our boat

Energy Consumption

In this lesson, we will look at all loads on the boat and determine their energy consumption for different scenarios.

Energy Storage

To store the energy between charge interval, we have to carefully design our battery banks. In this lesson we look at various options for batteries depending on our calculations from the previous two lessons.

Energy Generation

Now we look at the supply side and determine the available charging sources such as shorepower chargers, alternators and renewable energy sources and their required output to keep up with our energy needs.