pracTical
What’s inside a typical
deep-cycle battery.
Upgrade your electrics
Duncan Kent
Part 1: All you need to know about batteries
discusses the
vagaries of the Today, a typical cruising yacht uses four times energy through a chemical reaction between two
different types of
as much electrical power as was considered different metal plates, immersed in a solution
necessary just 20 years ago. There are many called an electrolyte. In short, the negative plates
marine batteries
myths around the ‘best’ policy to fulfil this are made from sponge lead metal, the positive
available and
increased energy demand, so over the next three plates from lead dioxide and the electrolyte
issues we will be explaining how to attain a is a solution of sulphuric acid. When the two
explains which is
simple, but sensibly balanced system that will different metals are immersed in an electrolyte a
best for each
supply all your needs without breaking the bank ‘potential difference’ is created between the two
or requiring a science degree to understand it. plates, which, in the case of a lead acid battery,
job – and why.
In this, Part 1 of our new practical series, is approximately 2.125V per cell.
we look at what is available and what is new
in battery technology and how it can be put to Choosing the right battery
good use by the cruising boat owner. For a boat that is used for short passages and
Part 2 will cover AC charging methods reasonably brief cruises, semi-traction lead-acid
in detail and Part 3 will explain the various batteries are a relatively cheap option, providing
methods of onboard charging and how to control their limitations are understood. The advantages
your power system to your best advantage. are that you needn’t separate the starter and
service banks, which simplifies the switching
How a battery works and charging systems considerably. Many
To keep it simple – a typical lead-acid marine cruisers use large lorry batteries and consider
battery is made up from six 2.125V ‘cells’ them to be perfectly adequate. This may be
connected together in series to produce 12.75V true, providing you don’t ever allow them to
at its terminals. Each cell creates electrical discharge too deeply and you ensure they are
110 Sailing Today July 09
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