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Many sailors want the comfort and convenience of using standard household appliances on board, yet away from the dock an alternative source of AC power must be provided. Generators are an option, but they don't match the freedom and quiet operation of DC-to-AC power
inverters. If your total AC load is moderate and your battery capacity and charging system sufficient, an
inverter can eliminate the need for any other AC power source.
WHAT THEY DO
Inverters take DC power stored in a battery bank and convert it to household AC power. They simultaneously raise the voltage and invert direct current to alternating current, then supply this electricity either directly to an AC outlet on the inverter (on smaller models) or directly to hard-wired AC circuits on board. The power they draw from the batteries must be replaced on a routine basis.
To estimate how much electricity an inverter draws from a battery bank:
- Multiply the total AC appliance power draw (in watts) by the number of hours the inverter operates to get the total watt-hours of energy consumed.
- Multiply this number by 1.1 to 1.2 to account for inverter inefficiency.
- Divide this number by the DC system voltage to convert to amp-hours of battery power consumed.
For example, a 72-watt TV/VCR combination operating from a 12-volt inverter for two hours would consume roughly 14 amp-hours of battery power, whereas a microwave oven drawing 1000 watts for 20 minutes would consume roughly 32 amp-hours of battery power.
WHAT THEY DON’T DO
Loads that are not supplied by inverters include:
- AC to DC battery chargers; in essence, trying to use battery power to charge the batteries.
- Air conditioning, unless supplemented by an engine-driven, high-output charging source.
- Appliances with large heating elements such as hot water heaters, space heaters, and electric ranges.
- A few appliances with multiple, digital timers, notably bread makers, have difficulty running from inverters with a modified sine wave form.
A generator best satisfies these loads when the boat is away from dockside power.
PROPERTIES
Initial Surge and Continuous Power Output In Watts
- An inverter's size and weight are proportional to its rated output, and also to whether it is designed to operate as a battery charger.
- Inverters come in a wide variety of continuous rated outputs, from small 50-250-watt pocket inverters ideal for powering computers, radios, tape decks, TVs and VCRs to large units of 3,000 watts or more.
DC Input Voltage
- Typical inverters operate on either 12 or 24-volt DC input voltage ranges.
- Most inverters are equipped with low battery cutout protection that prevents the inverter from working if the battery voltage drops below a pre-set or adjustable voltage set point.
AC Output Voltage
- Inverters are available with either 120VAC/60Hz output (North American models) or 220VAC/50Hz output (European models).
- Waveform - Most inverters on the market produce modified sine wave power, which roughly approximates sine wave power produced by the utility. Modified sine wave inverters are less expensive, more efficient, and work well for almost all appliances. Inverters that produce utility-grade sine wave power can operate any AC appliance without harm and are a good choice for sensitive electronic AC loads.
ACCESSORIES
- Fuse as recommended by the manufacturer.
- Remote control panel/monitor to display voltage and amps, inverter On/Off control and charger status as a minimum.
TIPS
Inverters are quiet, making them perfect for computers and other work-related appliances, as well as stereos, TVs and VCRs, even kitchen appliances.
INSTALLATION
Fundamentals of DC electrical systems and a complete electrical toolbox are required for inverter installations.
Toolbox
- Screwdriver
- Drill and bits
- Bolts, nuts, and washers
- Soldering iron if required for connectors
- Multi-meter
- Wire ties and clips
- Tin-plated wire
- Terminal connectors
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