Boat Electrics

Boat renovation requires you to think ahead and in some cases study ahead otherwise your project frequently becomes stalled by questions such as ‘what should I do next?’ and ‘how on earth do I do that?’ So for me, bedtime reading during this period of intensive  Gel-coat sanding has centered on trying to gain an understanding of 12 Volt electrical systems and methods of keeping juice in the wires when I’m not hooked up to a land-line on a pontoon.

I had kind of hoped to make a technological leap when I came to considering what my power needs might be. I already have a handheld GPS and VHF so I thought I might be able to go for a very simple system, maybe supported by an Apple I’pad  or something but the more I thought about how I wanted to use the boat and what that meant for power (in and out) the more complicated it seemed to become, especially for me who doesn't know the difference between an Amp, and a Volt.

I don’t claim to be a fast learner but I do know that if I’m told something three times (preferably in three different ways) then I have a chance of understanding and retaining the knowledge. Three books were particularly useful. You’ll find them listed below. Now I’m living in a country district in France so its hardly likely that I’m going to put my hands on these books in my local book store twelve miles away – so thank goodness for the internet and, for people in similar circumstances, the book titles below are links to a trusted supplier. If I were to purchase just one of these books it would be the 12 Volt Bible – but in truth I must confess I needed all three.

I bought mine with the intention of selling them on later --- in retrospect I think it’s a better idea to keep hold of my copies.

It would be impossible to cram all the information on 12 Volt boat systems into one blog post but here is a very brief synopsis of the logical steps in system design and the processes you need to go through to get yourself started.

Essentially you need to consider what kind of sailing you intend to do and list the electronic equipment you will require:

            Echo sounder or fish finder?

            VHF Radio?

            GPS?

            Navigation lights?

            Autohelm?

            Comapss light?

            Cabin Lights?

            Sound system?

            Electric bilge pump?

            Domestic water heater and pump?

The list can be as long or as short as you feel you need. To my list I added a bank of 12 Volt plugs so that I can always plug in additional equipment or recharge hand held stuff.

The next step is to calculate the ’power drain’ that these items will inflict on your batteries. Careful thought is required at this stage. The packaging and product information will give you and idea of how many amps a given piece of equipment will require when in use but you will have to determine how many hours you are likely to have it turned on for a given stretch of time. 12 Volt direct current also weakens according to the distance it has to travel from the power source to the equipment so you have to accommodate that in your calculation in order to get an idea of the amount of power you need to be able to store (one battery, two or more!). Thought also needs to be given to choice of batteries. Automotive (car) batteries can be less than idea – they are built to provide an enormous power hit over a brief period to start an. Boat equipment however, has a much smaller requirement but will expect power to be provided over a much longer period. A deep cycle battery is therefore more useful. Then thought has to be given as to how you will keep your batteries charged. One way is to use a 24 Volt landline from the pontoon – but at sea, can you keep the batteries topped up using you boat engine, or is solar or wind turbine power more appropriate to your needs? Some would argue that the best idea is to install both systems  so that you have an option of any given circumstance. Finally, you’ll need some mechanism to stop batteries charging when they are full – otherwise they may overheat. If you are considering a 24 volt recharge capability why not also think about dockside comfort and opt for a 24 volt domestic circuit for use while in port?

OK there is a great deal to think about and I’ll let you know how I get on – but if you’re considering tackling your boat’s electrics please remember 12 Volts are unlikely to kill you but a badly set up 12 Volt system can start fires. 24 Volt domestic electricity is always dangerous if it isn't correctly installed but close to water the dangers multiply enormously.

Here are those books I found most useful: 

Title:   The 12-Volt Bible for Boats (Second Edition)(USA Readers)
(UK Readers Click here)
UK

Author: Miner Brotherton Revised by E Sherman      

Publisher: International Marine / Mc Graw Hill

ISBN    978-0-07-139233-4

This is a complete introduction to the 12 electrical system you are probably going to want to use on your boat. It explains how the system works and how to install maintain and troubleshoot problems. If you are installing your own system it offers the basic information and it should be your first port of call for most answers.

Title:    Understanding Boat Wiring (USA Readers)
Understanding Boat Wiring (UK Readers)

Author: John C Payne  

Publisher:  Sheridan House

ISBN       1-57409-163-8

The book is a very practical guide to planning and installing wiring on your boat. It establishes the standards to which you should be working, explains electrical principles, circuit protection and isolation, switchboards and panels, systems for earthing circuits.

Title: Understanding Boat Batteries and Battery Charging (USA Readers)
Understanding Boat Batteries and Battery Charging (UK Readers)

Author: John C Payne  

Publisher: Sheridan House

ISBN  1-57409-162-X

Whereas the previous book dealt mainly with power distribution around your boat to drive the electrical systems and equipment on board, this book explains how to choose and install the sources of that power (the battery or batteries) and how to keep those storage cells charged and functioning. I would recommend that this book be read in conjunction with Understanding Boat Wiring (above).

Finally, thanks to significant correspondence from readers, it has become clear that many of us are working in remote locations and that the issue of sourcing materials equipment, tools and information is a central concern to us all. With this in mind you now find a new Page on this site : ‘Seaward’s Boatshed’.  As time goes by you will find here a growing list of all the books and tools I have used and found useful with links to trusted suppliers. In keeping with my own self imposed site policy explained on the ‘Homepage’ however, you’ll only find gear listed here that I have found to be reliable and useful. Other gear may be just as good but if I haven’t had first hand experience of it or if it has let me down – then I can’t recommend it and you won’t find it listed.

Seaward