Is it time for a new Inverter?

By Jeff Cote, Pacific Yacht Systems

Mooring and cruising has never been more convenient for boaters with onboard inverters. If your inverter is more than 10 years old, it just might be time to upgrade. Here are some options.

Inverters are not new in the boating world. They have been providing boaters with all of the comforts of home since the early 1980s. Staying on top of your boat’s systems is essential – inverters included – and when it fails miles from shore your power options become limited.

The two dominant types of inverters we see in the marine industry are modified and pure or true sine. Many boaters still have modified sine wave inverters on their boats and they work well for most resistive loads, including lights and coffee makers, but have a hard time running any inductive loads, such as microwaves and TVs.

Modified sine wave inverters were once the most common among boaters and are the least expensive. Pure sine wave can manage all AC loads and are effective for AC inductive loads needed for laptops, battery chargers for cordless tools, dimmers, and stereos. In addition to producing more efficient and cleaner power like that in your home, the price difference between modified and pure sine wave has narrowed. Considering the benefits, most boat owners are choosing pure sine wave inverters.

Know the Benefits of Modern Inverters

The capabilities of modern inverters are two-fold. Not only can they change direct current (DC) to alternating current (AC) or 12V DC to 120V AC, they include multi-stage chargers designed to maintain batteries by conditioning them to manufacturers’ specifications. Proper conditioning leads to longer battery life.

If your inverter is more than 10 years old, it may be time to consider replacing it. While it’s important to replace an inverter before it quits, the new inverter/chargers feature very cool new functions. When choosing an inverter think carefully about these factors:

1. Size: Inverters vary in size and are gauged by wattage. The larger the inverter, the more devices you can run simultaneously. From our experience, the most popular size is 2,000 watts.

2. Type: There are two types of inverters, a modified sine wave and true sine wave. We recommend purchasing a true sine wave for better performance in the long run. The higher cost is worth it. The disadvantages associated with having a modified sine wave inverter often override its lower cost.

3. Cost-Effectiveness: Most large inverters come with battery chargers. Purchasing a larger inverter/charger is more cost effective than purchasing two separate devices.

What’s Available for You?

In 1992, Xantrex launched a line of inverter/chargers called Freedom, specifically for the recreational marine and RV markets. These became one of the most popular inverters on the market and we still see boaters using them today. The most recent addition is the Freedom SW series. This is a pure sine inverter that can stack with other Freedom SW inverters. You could stack two 3000W inverters for a total of 6000W, which could actually run an air conditioner.

Another great innovation from inverter manufacturers is the automatic generator start (AGS) function. The controller will automatically start your generator based on battery voltage, and then automatically stop after a pre-programmed amount of time. You can even program during quiet times, so your generator won’t wake up the entire bay in early hours of the morning.

Inverter companies are also embracing onboard Wi-Fi to offer advanced onboard power management systems. Products like the Xantrex, Conext ComBox and the Magnum MagWeb offer live monitoring of the inverter, battery monitor and automatic generator start modules. For instance, current conditions, settings, summaries, faults, and battery monitor statuses can be viewed via a web-based portal or a smart phone app. You can even be alerted via email or text if there is an issue.

One of the significant installation challenges of replacing an inverter/charger is that older models would often use a telephone cord for connection on board your boat and the newer models use an Ethernet cable. This meant spending hours removing the old cable and running the new cable. Companies, such as Xantrex, now offer a telephone network cable adapter that simply plugs into the old cable so you don’t have to run a new cable.

Every year we perform electrical audits on boats and always see the same installation mistakes. If you are installing an inverter/charger on your boat, avoid these common pitfalls:

1. Having no on/off switch on the DC-positive inverter wiring. ABYC codes require an on/off switch. When servicing AC circuits on your boat, you need to disconnect the inverter. An on/off switch on the DC side is critical to ensure that the inverter is off.

2. There are fusing issues. Inverters require very precise fusing. So, it’s important to follow ABYC standards, along with the manufacturer’s recommendations. These are the most common issues:

  • There is no fuse.
  • The fuse is located at the end of the circuit. This is incorrect. The fuse should be closer to the batteries, not the inverter.
  • The wrong type of fuse was installed. Inverters require a Class T fuse, not an ANL fuse.
  • The fuse is the wrong size. You must install the fuse to the exact recommendation of the manufacturer.

3. The inverter is in the wrong area on the boat. Inverters are not ignition-protected and cannot be installed in a potentially explosive environment such as a gasoline engine room.

4. Large AC loads are wired to the inverter. Appliances such as water heaters and stovetops have large AC loads. Such large loads should be avoided on any inverter because they deplete the batteries. As a general rule, heat should never be created from battery power, because it consumes too much energy. It’s better to use a generator or connect to shore power for large AC loads.

5. The chassis ground connections use 10- or 12-gauge wiring. Since an inverter has both AC and DC connections, the chassis ground connection must protect up to the largest wire. Therefore, chassis ground connections should always be equal to or one size smaller than the largest DC wire feeding the inverter.

Advancements in inverter/charger technology have been another game changer for the marine industry. Boaters are no longer required to install two different units, incur almost twice the costs, and sacrifice twice the space. The new inverter/chargers have a smaller footprint, are more efficient, offer smart charge capabilities and come with a lot of new and user-friendly features.

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