The days when Joshua Slocum sailed with nothing more than an alarm clock without a minute hand are the stuff of legend. They are also long gone. Today's cruisers are more accustomed to having all the comforts aboard their floating homes.
There are valid reasons to have 110-volt AC power on board a cruising boat beyond such luxuries as having a blender to mix frozen margaritas. The ability to use power tools in remote locations can be a real lifesaver. Our sewing machine has repaired torn sails at sea in a few minutes, replacing days of work with a palm and needle. Using a small sander to care for teak while at anchor helps keeping the boat bristol an easier proposition. Many useful cruising products rely on rechargeable batteries for power, requiring a periodic drink from the 110-volt well.
Until the past decade, having 110 volts on board meant having a motor-generator set. While they certainly have their uses, generators take a great deal of space, are expensive to install and maintain, and create both noise and exhaust pollution that are an anathema to sailors in a quiet harbor.
Mounting inverters close to the batteries will allow you to reduce the length of the 12-volt cables.
As power-hungry 12-volt devices such as SSB radio, radar, refrigeration, and entertainment equipment found their way aboard, 12-volt systems became beefier and more sophisticated. Alternators, solar panels and wind generators, monitors, and even the batteries themselves were improved, and were instantly adopted by the cruising community. When working inverters were finally perfected in the late 1980s, they were an immediate hit with those already prepared to step that extra 12-volt energy up to 110 volts.
So, go ahead! Feel free to run the coffeemaker, the hair dryer, the electric drill, the microwave, TV, and VCR while sailing. Charge up the cell-phone battery and rechargeable searchlight while you're at it. Make a copy of this article on the computer printer out at the anchorage. But remember that the system has to be sized and installed properly, and that the 12-volt power has to be replaced. Here are some tips:
Size Don't overload an inverter. Figure out what loads you'll use simultaneously, add the wattage up, and then buy an inverter with a 20 percent larger rating than you think you'll need. If you want to run a 1,000-watt microwave, spend a few extra dollars to get the 1,200-watt inverter—better yet, get the 1,500-watt model, as we all tend to find more uses for the beast once it's installed.
Options Many large inverters have powerful, multi-stage battery chargers built in, and these are valuable if you have a small, older charger to replace. Most inverters with battery chargers now have automatic switchover from the inverter mode to battery charger mode when the shorepower is connected. If yours doesn't, a "Ship/Shore" safety switch will be mandatory. Some inverter/charger combinations have independent charging capability for multiple battery banks, while others offer this as an option. A remote control is a good option if you are mounting the inverter in an out-of-the-way place. Fancy monitors and regulators, however, can amount to an expensive luxury.
A fuse in the 12-volt line is a safety imperative.
Installation The first thing required is that the battery bank capacity and condition be up to the tasks ahead of them. If the banks are too small, or too tired, to run the large loads of an inverter, enlarge or replace the storage system when installing any inverter. All inverter installations require a fuse in the main 12-volt input line—this is not a place to save money as the fuse is a major safety item. Do not extend the 12-volt lines very much, if at all. If the lines are extended, use the same gauge wire as supplied on the invertor, or heavier, from the fuse block all the way to the battery connections. Insure that all battery switches, disconnects, and terminal blocks are rated to match or exceed the maximum load. The installation area must obviously be dry, but also well ventilated as inverters can generate a great deal of heat. Inverters are heavy, and must be firmly bolted down. By all means, read and follow the manufacturer's instruction manual, and be careful to disconnect both the shorepower cord and batteries before attempting to re-wire the system.
Usage A modern inverter will run any 110-volt appliance without difficulty—almost. There are exceptions:
Be aware that very small loads, such as recharging your handheld VHF battery, may not create enough load to trip the inverter out of its "idle" mode. It is sometimes necessary to plug in multiple small loads at the same time to signal the inverter that a 110-volt demand is present. An alternative is to plug in a light or other, larger load along with the small one to wake the inverter out of its sleep mode.
A small number of electrical appliances contain intricate electronic timing devices that will not operate from an inverter's "square wave" output. Chief among these are bread makers, where the timers establish the mixing, rising, kneading, and baking sequence.
Inverters can gobble a tremendous amount of 12-volt power in a hurry. The rate of exchange between 12-volt and 110-volt systems is roughly 10-to-1, stated in terms of amps—a motor that draws three amps at 110-volts (330 watts) will consume nearly 30 amps at 12 Volts (360 watts). Don't forget to replace the batteries' stored energy before the well goes dry, and that may require a bigger alternator or an alternative energy source.
Once the magic inversion box is wired into the ship's systems, sit back and enjoy the silence and the power.