For a long time I have been a 12 volt man aboard our trawler, the Patricia Ann. Twelve volt DC systems were always simple, not dangerous and served their purposes. But after a recent five-day journey on our trawler where we had to continually start up the generator to supply electrical power to the 115 volt ac freezer to sustain temperatures, I started to think about alternate options. We put over 90 hours on the genset in just 5 days; time for one more oil change!

So I began to think about adding an inverter to run the freezer. But what is an inverter anyway? An inverter is an electrical piece of equipment that changes battery direct current (dc) power to alternating current (ac). But there are a lot of alternatives from which to select, where do I start? When it comes to deciding on a power inverter for your boat, the alternatives can be puzzling. With a lot of options on the market, it is valuable to comprehend what the differences are so that you can make the best choice for your own boat application. Your primary concern will be wattage. Inverters are sized by the wattage they can handle. Consider what things you will be running and how many amps each item needs. You will need to also think about the number of them you will be operating at the same time to determine which size inverter will be the best for your needs. You do not want to overload your inverter by turning on many high wattage items at the same time. You will most likely notice that the price tag of inverters rise with the quantity of wattage. You can get the wattage by looking at the manufacturer's label on the piece of equipment. If only the amps are shown use the formula (amps x 115 volts= wattage) to convert to watts.

The next issue will likely be if you should get a true sine wave inverter or a modified sine inverter. A true sine inverter is one that will give you a nice current much like you get from the electric company. A modified sine inverter is to some extent less pure. The modified sine inverter was made as a more cost effective option to the true sine inverter. You will learn that even though the pure sine inverter will give the finest electrical flow, it also will be the most expensive. An 1800 watt modified sine inverter will amount to about $350.00.

Although the modified sine inverter is more affordable, it has its individual issues. For a good number of smaller appliances, for instance a refrigerator or hair dryer, a modified sine inverter will be sufficient. On the other hand, with several appliances like plasma televisions you might see a lack of precision. In this instance a true sine inverter might be a superior solution so that you can enjoy a better quality output. It is also vital to keep in mind that a modified sine inverter cannot be upgraded to a true sine inverter. You need to make certain you are buying the right inverter for your vessel's needs at the start.

It is a good idea to inquire with reference to overload turn off indicators or switches on your inverter just in case you overload the inverter; a good number of inverters contain them as standard equipment. You may also desire to research to find out if the inverter has thermal and short circuit shut down to prevent those kinds of emergencies as well. Additionally, a few inverters offer built-in shut down capabilities if the battery storage levels get to a specific low point.

I chose to install a Xantrex 1800 watt modified sine inverter capable of 1000 watts of continuous load. This inverter has a built-in transfer switch that transfers between shore and inverter power.

The final consideration is the battery bank on board your yacht you are going to be drawing from. Your inverter will be drawing from this battery bank and you should find a way to calculate how long the inverter can work before a recharge must take place. Examine your battery to obtain the amp-hours for them. Amp-hours represent amps time hours. A battery bank of 2 8D batteries will have about 580 amp hours.

So I know that my freezer draws 2 amps and works for 20 minutes each hour which equates to about 7 hours per 24 hours. So the entire amp-hours the freezer will use per 24 hours are 14. So in essence we could run the inverter for approximately 41 days without a recharge, but can we?

It isn't good to run a battery all the way down to zero. Battery life is directly linked to how deep the battery is cycled each time. If a boat battery is discharged to 50% every day, it will survive about twice as long as if it is cycled to 80% of full discharge each day. If cycled merely ten percent of discharge, it will last roughly 5 times as long as one cycled to fifty percent. This does NOT imply you are not able to go to 80% on occasion. It's simply that you should have some concept of the loads. You need to figure on a standard discharge of approximately 50% for the best storage vs cost factor. Also, there is an upper threshold - a battery that is constantly cycled 5% or less will usually not endure as long as one cycled down 10%. This happens because at extremely shallow cycles, the lead dioxide tends to build up on the positive plates. I prefer to cycle my batteries down 20% before recharging. Checking your batteries can be estimated but I prefer to make use of a Trimetric 2025 monitoring gadget. This electronic apparatus enables me to monitor the battery banks amp-hours use precisely.

With a little careful preparation, an inverter can make a boat trip a more enjoyable event.

After you pick the inverter that is right for your vessel, be sure to have it properly put in. If you aren't sure about working with electrical power, it will likely be best to have a professional do the task for you. Then you can be cruising away knowing that you have what you require to keep your boat running on enough power.

We went on another four-day cruise over the New Year holiday with our new inverter and I am happy to say we only operated the generator 6 hours in 4 days. Life is good.