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Forcing A Shore Power Plug to Fit

Putting around peg into a square hole. Why it is a bad idea.

Pros and Cons of a Traditional Isolation Transformer

A marine isolation transformer is a versatile device that can be used to provide galvanic isolation from shore power systems, to enhance electrical safety and eliminate corrosion caused by stray currents. Some isolation transformers can also be used for raising the shore voltage to deal with voltage drop. Another common use is to adapt the vessel’s internal power system voltage to a higher or lower shore power supply. If isolation transformers are so useful why is every boat not equipped with one?

Charge Distribution

Quite often on boats there will be more than one battery bank that will be charged from a single source, as is very common with an alternator. There are several ways of distributing the power from the charging source to the various batteries allowing prioritization of current flow.


Early electrical pioneers discovered that passing a magnet in close proximity to coiled wire induced an electrical charge, and that a rotating magnet in front of coiled wire created alternating current. This electrical principle is the basis of an alternator. An alternator is a rotating machine designed to produce alternating current that can then be rectified to produce directional current that can be used, or stored for later use in a battery.

Solar Charge Controllers

Solar energy is becoming a very common addition to many boat’s electrical systems as an alternative charging source for their battery bank. Solar energy is harvested by photo-voltaic cells converting the light energy, photons, into direct current that can then be stored in a battery bank; however, like all charging sources it is important that the charge is controlled to prevent battery damage.

Shore Power Connections

With the coming of fall and cooler weather, there will inevitably be some concerned boat owners having a closer look at their shore power connections. Many boats will soon, if they are not already, be tied to the dock for the duration of the ‘off-season’ with the exception of possibly a couple of forays on spectacular or special days. Most people will leave their AC electrical system connected to the shore side utility to run the battery charger and maintain the batteries

Connecting and Disconnecting from Shore Power

There is a suggested sequence for connecting and disconnecting from shore power and sound reasoning for it. When connecting to shore power, first make sure the main AC disconnect switch is in the “off” position and connect to the boat side inlet before connecting to the...

AC Reverse Polarity Indicator

An important part of a boat’s AC shore power system is the reverse polarity indicator light. Typically, power to a 120VAC system is delivered on three lines. A reverse polarity situation arises when the hot and neutral lines are inadvertently crossed making the neutral “hot”.

Double Pole AC Circuit Breaker

Most boats have a shore power inlet to plug into dockside power. The power supplied is AC (alternating current), and it is usually available in 240V/120V, with a 30A, 50A or 100A service offered. Most mid-sized boats (32 to 45 foot) will have a 30A inlet installed, as original equipment...

More Energy: Reducing Your Power Needs

Anyone that has ever lifted a battery knows that they are quite heavy and bulky. In many cases the demand for power on a boat is greater than the space that is available to hold the battery banks. In these instances...

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