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The electrical systems and their dimensioning are one of the most debated subjects during the preparation of an ocean-going yacht, and for a reason!   Unlike a typical summer-cruising boat which at worst will spend few days far from a shore-power plug, an ocean-going boat will spend extended periods of total electrical self-sufficiency while powering a wider set of electrical equipment!

Fundamentally, all the fuzz about electrical systems boils down to two questions:

  • how many batteries will I have to fit on-board, and of what size?
     

  • what's needed to recharge the batteries, and how long will it take?

In a production-boat, the yard probably answered these questions already with a straight-forward solution: 2 Lead-Acid automotive batteries, typically around 100 Amp-hours (Ah) each, one dedicated to feed the on-board services ("House"- or "Service"-battery) and the other reserved for engine-starting ("Engine"- or "Start"-battery), and in the few cases when the boat will not be connected to shore-power during the night running the engine for an hour will do.

Too easy!    On a seafaring boat there are a number of complications:

  • the daily consumption is high, because there are more devices and they are powered through the 24 hours, so a 100 Ah battery is not enough or it would not last 24 hours and would need to be charged more frequently.
     

  • the engine would take several hours to perform a daily recharge, building up (in a sense, waisting) precious engine-hours and using a lot of fuel.
     

  • failures must be taken into account, so a backup recharging system must be foreseen.
     

  • it would also be desirable to recharge using "green" methods, taking advantage of natural resources such as wind, sunlight, the boat's motion through the water, therefore reducing (if not downright eliminating) the use of the engine and providing a backup recharging system.
     

OK then, let's tackle the subject of ELECTRICAL SYSTEM DIMENSIONING (batteries and charging systems).
 

      

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Last Update: 11/11/2014

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