Inverters for Your Solar Power System

What are Inverters?

An inverter is an electrical device that turns 12 volt DC current into 110-120 volts AC current for use in powering your household electrical devices. Or what ever devices you have that run on 110-115 AC current.

The name inverter comes from when the voltage from power plants had not yet been standardized. Many people used this non standardized power source to power motors. Because of the different voltages one could find at the outlet, converters were used to change the AC voltage into a known DC voltage so as not to damage the motor, and thus the name inverter was used for devices that did the opposite as in converting DC to AC current which present day inverters do.

Why Do I Need an Inverter

The answer to that involves the construct of usable energy.

Usable Energy is energy that can be used to do a certain task, in this case, run your household electrical devices.

Everything in the known Universe is made up of energy. Matter is just an exotic form of energy, E=mc2. So why can't I just plug my TV into the ground? Because it is not energy that can be used by your TV.

There are, according to Google, millions of sites on the Internet dedicated to free energy. People spend huge amounts of money looking for and trying to develop free energy devices. Hello, free energy is everywhere. It's the act of turning this free energy into usable energy that is the show stopper. It's the converting of free energy into usable energy that's the hurdle. And cost is the major factor.

For the consumer, wind and solar energy harvesting are the only two affordable options as of this writing.

The inverter is one of the items used in converting solar energy into usable energy. The solar panels convert sun light into electrical energy. The charge controller converts the 20 or so volts from the solar panels, depending on your solar system, into 12 to 14 plus volts, for a 12 volt system, used by your batteries and inverters. The inverter converts the voltage from the charge controller and/or batteries into 110-115 AC volts used by most household electrical devices.

If you want to run that TV or fridge from the power that you harvest from your solar panels then you need to convert that energy from the solar panels to energy that your electrical devices have been designed to use or buy devices that are designed to run on 12 volts, but you will still need to regulate that voltage from the charge controller/batteries because that voltage is not a constant 12 volts but varies from 11 to 14 plus volts.

Most inverters have been designed to work with 11 to 14 plus volts and will give you a usable 110 – 115 volts AC that can be used by most household electrical devices.

Modified and Pure Sine Wave Inverters

There are two types of Inverters, modified sine wave and pure sine wave inverters.

Pure sine wave inverters are inverters that produce a voltage that most closely matches the voltage from commercial power plants. Pure sine wave inverters will run most anything that uses 110 to 115 volts AC from commercial power plants. But they are much more expensive than modified sine wave inverters, putting them out of reach of many who are developing a DIY solar system.

Modified waveform inverters have more of a square wave rather than a sine wave, which is only a problem when running inductive type electrical devices like motors. Running resistive devices such as lights and most TV, computers, and radios will not give you any problems. Some clocks will give you problems because they use the sine wave to determine the speed of the clock which will not work correctly when powered by a modified sine wave inverter.

But I have been using a modified waveform inverter to run my fridge and freezer for over a year now with no problems at all. The fridge does have to work a bit harder and hotter with a modified sine wave but with the newer fridges and freezers this is less of a problem. Older fans have a problem with modified waveforms but newer fans, if run on high, tend to work just fine.

Most web sites will tell you to contact the manufacture to learn if your device will work properly with a modified waveform but I don't speak Chinese and I doubt anyone that you would be able to contact would have proper knowledge of whether their devices would have problems with a modified sine wave inverter.

I have found that trial and error to be the best way to find out if your devices work well with a modified sine wave.

What Size Inverter Do I Need?

This really depends on what you plan on running with your inverter. A good way of thinking is to plan on getting an inverter that will provide at least three times the power you will need. If that sounds like over kill consider that a fridge or freezer will take up to three time their rated power use to start. And power tools will suck down huge amounts of power when put under heavy loads. If these power tools don't get the power they need they cook.

Also consumer devices are not designed to work at maximum load. To keep prices down consumer products don't use top notch components so to counter this it's best to buy things that are rated well above what you plan to use them for.

I have a 2500 watt modified waveform inverter that I use for all my heavy lifting like freezers, fridges and power tools. This is well above what I will ever use. But when I'm drilling an inch hole in hard wood my drill doesn't drag in the slightest as it has all the power it needs when it needs it. Also nothing dims when my fridge or freezer starts. I figure I'm only using at most 500 watts with everything running, but I'm covered for any surges of power I need like the fridge and freezer starting at the same time and the power tools when they need that extra power.

Now this 2500 watt inverter of mine uses about an amp just to run. That's a lot of wasted power if you only have three 66 amp hour batteries like I do, so during the night I don't run any fridges or freezers and I run my LED light directly off the batteries. But what I do is run a 400 watt inverter that uses less than a few milliamps of self consumption for running my TVs and whatnots.

So you may find it beneficial to have two inverters, one powerful one for the heavy lifting during the day when power is over flowing and a small inverter for night time necessities. All of this is only necessary if you don't have thousands of dollars for batteries.

Points to Remember When Choosing an Inverter

Pure sine wave inverters produce a current that most resembles the current from the grid, which will run your devices with motors a lot better in terms of power and heat. You may also find that some of your electrical devices just won't run correctly with a modified waveform. The down side is that pure sine wave inverters are a lot more expensive than modified waveform inverters.

Modified waveform inverters are inverters that give you a more square waveform than a sine wave, but I have found that most newer devices run just fine with this waveform. Modified waveform inverters are inexpensive and there are many makes and models to choose from. I have been running my fridge and freezer for over a year now with no problems. My power tools love the modified waveform and my 2500 watt Whistler inverter from Amazon has been running for over two years now and pumps out all the wattage I could ever need.

The size of the inverter should be around three times what you plan to use it for, reason being is that consumer products don't always use the best components and this is a way to ensure your unit will last a lot longer than if you buy an undervalued unit and push it to burn out.

Also most devices that utilize motors will need a starting current that sometimes will be up to three times the rates power of the device, like refrigerators and freezers.

Having two inverters is a good idea. Having a powerful inverter for day time use when power is plentiful, and for night time use so as not to run down your batteries a smaller inverter for the night necessities will give you added life to your batteries.

The more powerful the inverter the more power it will use just to run its self. My 2500 watt inverter uses over an amp in self consumption, were as the 400 watt inverter uses less than .5 amps to run its self.

A good practice is to convert as many of your electrical devices to 12 volts, that way you can run them directly off the batteries and for some reason the batteries love it and give what seems more power than if an inverter is used. Inverters use a lot of power when converting 12 volts DC to 110 to 115 volts AC, and the more power they convert the more power they use in doing that above what will come out of the inverter.

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