All About Inverters!
An inverter is a box full of electronic goodies that will convert your battery voltage into mains type power.
Once upon a time if you wanted to get "mains" type power from your battery bank you used a device called a rotary inverter. This was simply a battery powered motor spinning generator with an output similar to mains power. As you can probably imagine efficiency was somewhat lacking ...
The modern inverter is so efficient and reliable that using appliances powered directly from the battery, as was the norm in the past, is now all but history excepting motor homes, caravans and camp sites.
The modern concept in solar design for anything other than a small camper van, 4WD or campsite is to power everything from "mains" type voltages "inverted" from the battery bank. The advantage this gives us is that we can go shopping in a local electrical store and buy conventional appliances just like the common folk on grid fed power. Take the humble light globe for an example: A 12 volt device that gives good light output for a reasonable power consumption is getting hard to find and somewhat expensive. Choosing 24 volts for your lighting makes light bulb hunting even more difficult. If you stick with mains voltage, efficient bulbs are available from the local supermarket.
To sum up ... You need an inverter to utilise the power your solar system will produce! Without further ado lets look at what's in the box. BUT and its a BIG BUT ... An inverter is only as good as the battery bank it is connected to and that battery bank is only good if your power system is capable of charging it when needed!
The three ratings that should concern you when buying an inverter are:
1. Continuous Rating: This is the amount of power you could expect to use continuously without the inverter overheating and shutting down.
2. Half Hour Rating: This is very useful as the continuous rating may be to low to run say a large power tool or appliance but if the appliance was only to be used intermittently then the half hour rating may well be high enough to cover this.
3. Surge Rating: A high surge is required to start some appliances that once up and running may only need considerably less power to keep functioning. The inverter must be able to hold its surge rating for at least 5 seconds.
What the market can provide for you
The inverter market today will basically supply you with two inverter types:
Low Cost: These inverters are available from electrical stores, hardware stores and electronic suppliers are commonly available. Often you will find them sold by folk who know nothing of inverters or electricity. These inverters usually lack devices such as auto-start or any form of adjustability. Performance may or may not be as stated (or even not properly stated at all). However they are not all bad. Consider one if your needs are modest and your budget is limited. Usually they present no problems for TV and video, computers and smaller appliances. High output models can be good "power tool" inverters. We don't sell them.
High Quality: There is no substitute for quality. You will find only a small handful of companies worldwide who make high quality power inverters. You don't need a price tag here, one look will convince you of a superior product.
With a High Quality Inverter You will Get:
An auto-start system. An auto start allows an inverter to switch to a low power consumption standby state when nothing is connected and turned on. This will save you a lot of manual switching and/or wasted power
Adjustability. An ability to adjust parameters such as auto-start and battery depth of discharge is also helpful.
High quality heavy-duty power transformer. You wont see this unless you go poking around inside your box of electronic goodies but looking at the weight spec or picking up your quality inverter will demonstrate a heavy transformer inside.
Two Types of Electrical Wave
Your inverter will either be a modified sine wave variety or a sine wave variety. If you could see electricity you would notice a difference between two types. You may have to take my word on it here however if you can lay your hands on an oscilloscope (and work out how to use it) you can easily view the differences on the monitor.
Modified Sine Wave Inverters
Virtually all low cost inverters are "modified sine wave". A modified sine wave is easier and cheaper to produce than a sine wave inverter. It is also a fact that cheaper modified sine wave inverters have given this type of inverter a bad name. Very few "high quality" inverter manufacturers even make an inverter with this type of electrical output. If you buy a high quality modified sine wave inverter however you will get an inverter that will run 99% of everything electrical, have a higher surge rating and cost you less than a sine wave inverter.
Sine Wave Inverters - The Cutting Edge of Inverter Technology
A small bunch of inverter manufacturers worldwide have developed quality sine wave inverters to highly efficient levels. Efficiency has reached up to around 94% and the electricity from these devices is of a higher quality than grid power virtually anywhere in the world.
Choose a cheap modified sine wave inverter if your needs are modest and occasional.
Choose a high quality modified sine wave inverter if you want value for money.
Choose a high quality sine wave inverter if you want the best available.