Providing Electrical Power For Your Boat | Automotive Electrical

Many of the comforts aboard a boat need electricity and so a provision must be made to supply enough power. Lead-acid automotive batteries are the most common source. They can be recharged by the engine.

The first step is to work out the power requirement, and then see what recharging capacity is needed. For example, a single 12 volt interior light uses about 1 ampere. Navigation lights will probably use a total of about 2.5 amperes, a car type stereo disc player 0.5 of an ampere, and a portable compressor type fridge will use 2 to 4 amperes. Work out the number of hours that each will be likely to be on, and multiply this by the amperes each device uses. This gives the total power consumption in ampere hours (ah). A standard car battery has a capacity of about 50 ampere hours, but the main limitation may be the charging rate of the engines alternator. On marine engines there are typically 20 to 30 amperes maximum, and to recharge the 50ah battery would take more than two hours because the charging rate slows as the battery reaches full charge.

Weekend users and those without engines, have a way around this by fitting a solar panel which can top the battery up during the week. A 40 watt panel should satisfy a 50ah battery, but ensure that the panel has a diode to stop current flowing the wrong way. For power calculations use the equation (watts = volts x amperes) i.e. 40 watts = 12 volts at 3.3 amperes.

Radios use a lot more power when transmitting than receiving. Sound systems need a lot more power to shake the deck beams with heavy rock through 100 watt speakers, than to render a gentle melody played through small speakers.

Navigation lights are required on all boats moving at night. Vessels below 7 meters need an all round white light visible for 3.2 km. Craft of 12 meters or more need a white stern light visible through an arc of 67 degrees and a distance of 3.2 km, and port (red) and starboard (green), each visible from straight ahead to 112 degrees abeam and a distance of 3.2 km. A masthead light at least 2.5 m above the sidelights and visible for 4.8 km is also required. Yachts less than 12 meters need the same except that the stern light must be visible for 3.3 km and the sidelights 1.6 km.

Other lights vary enormously in price and range from circular nautical types which are operated by turning the glass, to small household wall units. Beware of cheap automotive reversing light types which have plastic covers that can overheat and melt when used inside. The caravan style of 12 volt neon lights are economical but can cause annoying radio interference.

When the sun goes down and you are out on the briny with only the hull around you and the mast and rigging above, it is nice to be prepared with the equipment and fittings which make the difference between a floating box and a home.

By: Tony D Manning

Source: http://www.pearlstreetjazzband.com/recreation-and-sports/providing-electrical-power-for-your-boat

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