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An inverter allows you to use your RV batteries to run AC appliances. They come in all sizes, and systems can be built to run everything from desk fans to air conditioners (if you have the battery power). All inverters are not equal, however. There are a few ways that these devices turn the DC power from your batteries into AC, and not all of them work well on all devices.

What is a sine wave?

The image above shows a sine wave. It’s a wave that oscillates between positive and negative numbers at the same rate over time. The next question is, how does that relate to electricity?

Direct current, or DC, flows in one direction through a circuit. To put it another way, when you hook up a battery to a lightbulb, the power flows out of the battery, in one end of the light, out the other end, and then follows the wire back into the battery. Graphing this electrical flow over time would result in a straight line.

Alternating current, or AC, moves both forward and backward. In other words, the power alternates direction. Keeping the graph above in mind, imagine the wavy line as electricity moving forward through a wire, then slowing to a stop, and then starting to move backward faster and faster until it reaches the opposite stopping point. This process happens over and over again. It’s kind of like rubbing your hands back and forth to create heat. The graph is a visual representation of that AC power sloshing back and forth.

The reason DC and AC differ in how they move has to do with how the power is typically generated. There is no need to go into detail about the mechanics of generating electricity, though. The main point here is that some electrical devices in our RVs like computers, LED lights, and phones run off DC power. Appliances like coffee makers, microwaves, fans, phone wall chargers, and TVs all require AC power in some capacity to function.

Unless you have a generator, which produces AC power, you are stuck with DC power from your RV’s batteries when your RV isn’t plugged in. An inverter will convert DC from your batteries into AC so that you can run AC appliances from your DC batteries.

How An Inverter Works

Imagine you have a flashlight powered by one battery. Since a battery is DC, the current will flow in one direction through the light to power it. Imagine you quickly take the battery out, flip it around, and put it back in the flashlight. The light would still work, but the current would be flowing in the opposite direction. If you could flip that battery around repeatedly at around 50 times a second, the current direction would be alternating.

That is precisely how a basic mechanical alternator works. Unfortunately, this method doesn’t produce a smooth sine wave because instead of the current gradually changing direction, it does so abruptly. The resulting wave looks like a square wave.

A square wave will run AC devices, but many of them don’t like it. Things with motors tend to overheat, and electronic devices with a computer chip may not function at all. Fortunately, you won’t find inverters that produce a simple square wave for the most part.

Most modern inverters use various electrical components to produce what is called a “modified sine wave.” In essence, they try to gradually alternate current directions like true AC. The resulting graph looks more like a stair-step pattern.

As you can see from the photo above, the modified sine wave looks a little bit like the pure sine wave pictured above. If your electrical device doesn’t need a pure sine wave inverter, such as an incandescent lightbulb, a heater, a toaster, or any other device that doesn’t really care what the quality of current is, then a modified sine wave inverter works great.

Unfortunately, when it comes to electronic devices such as computers, fluorescent lighting, speakers, AC motors (fans, refrigerators, air compressors), and some CPAP machines, a modified sine wave inverter doesn’t work as well. Aside from flickering lights and wacky computer issues, a modified sine wave inverter causes many devices to run inefficiently. In other words, power is lost in the form of heat. The result of devices running hot is a reduced lifespan.

Pure Sine Wave Inverters

A pure sine wave inverter, like the name implies, uses more expensive components that duplicate the pure sine wave that you would find coming out of a household plug. Anything you can run with a household plug will run just fine with a pure sine wave inverter.

Which one should you get?

It’s probably apparent by now that a pure sine wave inverter is the better of the two. Unfortunately, it is also the more expensive of the two. If you already have an inverter in your RV and are unsure of what type it is, your manual should tell you. If you don’t have a manual, you can always find the make and model on the device and google it to find out.

If you have a modified sine wave inverter, take a look at how you use it. Computers are probably not a good idea, but devices like laptop plugs that convert AC to DC with a rectifier will work fine. The disadvantage is it may wear out your laptop charger. If you run fans, fridges, or other devices with an AC motor using your modified sine wave inverter, they can prematurely wear. If you travel with a CPAP machine, make sure you confirm that it will run with a modified sine wave inverter, as some don’t.

Bottom Line

Upgrading to a pure sine wave inverter is the optimal choice, but most RVers can run many of the things they need with a cheaper modified sine wave inverter if it’s not in your budget. They just have to be aware of what they are plugging into it.

RV Technical Assistance Hotline

Basic electrical issues and other problems are common, and not everyone is an RV repair expert. However, did you know that your Coach-Net Premier Plan comes with access to the RV Technical Hotline? It’s available to you 24/7 to guide you through many common operational issues. Call the Roadside Assistance phone number on your member card to be connected to a technician.

About The Author: Levi Henley

Levi Henley and his wife, Natalie, have been full-time RVers for over 5 years. They have also been Coach-Net customers for the same amount of time.  They travel and workcamp around the U.S. in their 26-foot Itasca Sunstar motorhome with their two cats.  They write for multiple RV-related publications and recently co-wrote “Seasonal Workamping for a Living: How We Did It.” You can follow their adventures on the road at henleyshappytrails.com 

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