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Normally, the owner of a new boat does not need to worry about the on-board electrical distribution system: nowadays it is to be expected that the yard will do a decent job, in line with state-of-the-art technologies and in compliance with European technical standards.

A proper electrical distribution panel aboard Shaula3 (Alubat OVNI 385)

The situation can be totally different in the case of boats built before the coming into force of the European regulation, at a time when a boat's electrical system was supposed to power only the nav-lights and little more, as it has been the case for us with Shaula4:

Other times, other sensibility to the needs of a well-done electrical distribution system: the spaghetti-like wiring behind the panel in Shaula4!

Keeping in mind the good practices seen on Shaula3 and making reference to the european Regulation, with the help of good manuals such as Nigel Calder's excellent "Boatowner's Mechanical and Electrical Manual", we have been able to perform a thorough rebuild of the electrical system.

The instrument panel and the electrical distribution panel on Shaula4 at the end of the refurbishing work

An orderly distribution system, with properly-sized wires and quality switches and breakers, fulfills several objectives:

  • minimize the risk of fire due to over-heating of under-dimensioned wires
  • reduce the risk of malfunction due to oxidised or defective components
  • simplify fault-finding
  • ensure crew protection from electrical shock
  • prevent current leakages through the water and the consequent risk of galvanic currents
    (particularly critical for metal-hulled boats)


We spoke before about battery dimensioning, but not about the choice of battery TYPE, e.g. Lead-Acid, AGM, GEL or other even more exotic ones?

The battery bank on Shaula3: just 4 Lead-Acid-Silver "low-maintenance" batteries

Books have been written about this subject, so there is no point in repeating the whole story here; we debated the subject quite a lot at the time of Shaula3 preparation for long-distance sailing, given the potential for rough sailing there was a point in favour of GEL batteries, much less prone to spilling acid substances in case of capsize.    Unfortunately there are also drawbacks, beginning with the very high price and continuing with the need of dedicated charging devices.

In the end, we opted for the simplest solution: common automotive-like "low-maintenance" batteries, cheap and perfectly fitting in the available space.    During the circumnavigation one battery failed, possibly as a belated consequence of our capsize in the Caribbean, and we had to wait until Australia to replace it.    We had no other problem, and at the end of the voyage the batteries, which had been cycled at least 1000 times, were replaced with a modest expenditure: is it really worth it to go for more complex and expensive solutions?


Rules are clear: both the 220V shore-power feed (and, if present, gensets or inverters) as well as the 12V feed coming from the batteries, must have breakers or fuses capable of interrupting the current flow in case of a short-circuit.     It's important that these devices are as close as possible near the power source, but this must be reconciled with the devices' accessibility: a manual switch buried under a bunk would not be very useful in a hurry!!

The rules require a differential breaker within 50cm. from the shore-power socket, and battery cut-off switches as close as possible to the batteries themselves, provided they are easily accessible

Problem is that the cable from the battery terminals to the switch cannot be disconnected in case of a short-circuit, so the ideal would be to put a fuse on the wire, as near the battery as realistically feasible.    Even better would be an automatic breaker, which could be restored much more quickly in case of a "nuisance tripping"


Even on a very simple boat, at least a Volt-meter and possibly an Ammeter would be very useful to keep an eye on the batteries' charge status and the speed of charge/recharge; since some years more sophisticated instruments have become common, providing a somewhat more comprehensive picture of each battery bank's charge status, including Amp-hours supplied or received, % of charge, time-to-discharge, and so on.   Essential?  No, but useful for sure!

Battery management instrument (left)                           and (Right) an electric-leakage detector

On a metal-hulled boat there is another essential instrument: a detector of electric leakages towards the hull.

Why it is so important?  Because if the electrical circuits are in contact with the hull, there may be stray currents flowing through the water, causing electrolythic corrosion!    Besides, if the leak concerns the 220V circuits, the hull may become "hot", endangering the crew as well as people swimming near the boat.



Webmaster: Gianfranco Balducci - email: gfbalduc@tin.it

Last Update: 07/09/2017

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