These units don’t last forever, so avoid problems next cruising season by replacing your inverter this winter.
We can always gauge what is going on in the market place by the conversations we are having with our clients. One topic that has been coming up a lot lately, involves older modified sine-wave inverter/chargers, failing. And they aren’t failing in the driveway, they are failing while in use, in the middle of the vacation. It’s to be expected, these units are now 10 to 20 years old. An inverter/charger is a sophisticated piece of technology and, like other pieces of electronics, are not made to run forever.
Losing the benefits of an inverter will vary, many users only have an inverter to run convenience items like a TV or microwave while away from land-power. If your inverter fails, you can make do without it. However, for many, the inverter is critical as it runs the fridge while away from land-power or without the genset running. As well, many inverters also come with a charger, often referred to as an inverter/charger. While losing the inverter functionality will vary from user to user, losing the charger for the house batteries will most likely curtail a cruise for most users. A battery charger is essential to recharge the battery bank and to offset the DC loads while on land-power or running the genset to ensure that the batteries are not depleted. Without a charger, the only means of charging the batteries is via the alternators. This is fine if you are moving and going to new spots constantly, but what if you want to be in one spot or run the genset to recharge the batteries. Very quickly you will find yourself with depleted batteries and limited ways of recharging them.
Another difference between old and new technology, is the efficiency. An older inverter/charger offered about two thirds efficiency, the new units are 90 percent plus. For those who use inverters a lot, this will translate to significant power savings on your batteries and less draw provides a longer time between charges or a shorter charging time.
As we have mentioned in prior articles, there are two main types of inverters, modified and pure or true sine. Many users still have modified sine wave inverters and they work well for most resistive loads, such as lights and coffee pots, but have a hard time running any inductive loads, such as microwaves, TVs, and even modern coffee machines. Modified sine wave inverters used to be the most common and are the least expensive. Pure sine wave can handle all AC loads and are specifically good at handling AC inductive loads such as laptops, battery chargers for cordless tools, dimmers, sanders, polishers and stereos. Pure sine wave inverters produce a better, cleaner power, identical to that in your house. The price difference between modified and pure sine wave has narrowed and, considering the benefits, most boat owners are choosing pure sine wave inverters.
If you have a modified sine wave inverter of any age or a pure sine wave inverter that is over 10-15 years old, it may be time for an upgrade. So what should you consider when choosing a new inverter/charger? The first thing to take into account is the size of your existing battery bank. The challenge is matching your house bank, measured in amp-hours, to the inverter rating measured in watts. As a rule of thumb, we recommend a battery bank with a capacity sized at 20 percent of wattage. For instance, a 2,000-watt inverter should be connected to a 400 amp-hour battery bank. Inverters are available in all sizes, but the most popular choice is between 2000 to 3000 watts.
Next, calculate the draw or maximum concurrent AC loads you will run. Then decide the output of the charger, the larger the inverter wattage rating the larger the charger output. For instance, a 2000-watt inverter will provide a 100-amp charger at 12 VDC and a 3000-watt inverter will provide a 150 amp charger at 12 VDC. Depending on your battery size, you will want to have a charger that is at least 10 percent of battery capacity. With flooded lead acid batteries you can comfortably go to 20 percent of capacity. For instance, eight flooded golf carts in a 12 VDC bank will provide 880 amp-hours of capacity. With the minimum charge rate of 10 percent, the charger for this bank should be at least 88 amps.
Also remember, there are some high wattage loads that should not be run on the inverter such as a water heater, air conditioner, electric range or space heater. If you are using these items, you will need a generator or be connected to shore-power.
Replacing your inverter/charger is a good winter project and with many RV and boat shows just around the corner, you will have the opportunity to speak directly with manufacturers and installers. Before you go, make sure you know the size of your battery bank and how many amps you consume in a day, this will help with the decision making process.