cable and never had any problems with corrosion.
Your nearest motor factors will be able to supply cable
in large reels and the various cross sections you
will need. The simplest rule of thumb when deciding
the cable size for any particular use is “if in doubt
increase the size”. If the cable size is underspecified
then voltage drop will always be a problem but if you
oversize slightly then this problem will not arise. I
recently bought bought several large rolls of cable
from an eBay specialist making a big saving on
the way. This particular lot was ‘arctic’ cable that is
designed to remain flexible down to ridiculously cold
levels and is more heavily insulated than standard two
or three core cable. The only downside of this is that
it takes up more room in the trunking when running
through the boat.
Battery charging was dealt with as part of the wiring
scheme and it was decided to use Voltage Sensitive
Relays (VSR) for the split charging to ensure the
batteries were separated when not being charged.
This is an important factor in preventing the engine
start battery inadvertently being discharged while
using the domestic batteries. VSR’s are probably
the simplest and cheapest method of arranging a
split charge system as they are connected between
the engine start battery to which the alternator is
first connected and each domestic battery. Unlike
an ordinary relay that simply closes the circuit when
power is applied to it the VSR will not close until the
voltage in the primary battery (in this case the engine
start battery) reaches a pre-set level of something
13.8 volts. This tells the relay that the battery is being
charged and closes the circuit to allow current to flow
to all the batteries in the system.
If the domestic batteries are very low after long use
without charge then they may pull the engine start
battery voltage down to below the cut-out level. In
this case the VSR’s will open and allow the engine
start battery to build up its voltage level again before
passing current to the domestic batteries. There is
usually a delay built into the VSR to prevent it from
rapidly cycling on and off in this situation.With the batteries and electrical locker located
running the wiring could begin. You may recall that
early in this series during the initial construction
phase we glassed-in several lengths of plastic water-
pipe throughout the length of the boat to be used as
trunking for wiring and pipe-work. The value of this
unusual forethought could now be fully appreciated as
wiring could be run to any part of the boat by cutting
holes in the piping anywhere that wiring had to enter
or leave and then using a simple wire pull-through to
draw the cabling in and out of the piping. This was
particularly handy when running cables from the helm
position at the forward end of the wheelhouse to the
engine compartment right aft.
Along with the VSR’s each battery was equipped with
an isolating switch to ensure that everything is totally
disconnected when the boat is not being used. There
are a couple of exceptions here as both the automatic