What is a power inverter?

Do I need Modified Sine Wave, or Pure Sine Wave?

What size inverter should I buy?

What input voltage of the inverter i should choose? 12V or 24V?

Which solar system i should choose: on-grid or off-grid system?

How do I connect two or more batteries?

What is a power inverter?

A power inverter changes DC power from a battery into conventional AC power that you can use to operate all kinds of devices ... electric lights, kitchen appliances, microwaves, power tools, TVs, radios, computers, to name just a few. You just connect the inverter to a battery, and plug your AC devices into the inverter ... and you've got portable power ... whenever and wherever you need it.

The inverter draws its power from a 12 Volt battery (preferably deep-cycle), or several batteries wired in parallel. The battery will need to be recharged as the power is drawn out of it by the inverter. The battery can be recharged by running the automobile motor, or a gas generator, solar panels, or wind. Or you can use a battery charger plugged into an AC outlet to recharge the battery.

Do I need Modified Sine Wave, or Pure Sine Wave?

Some appliances are compatible with a modified sine wave; others are not. As a general rule, the more complex the appliance, the likelier it is that it requires a pure sine wave. But to be absolutely sure, you should always go by what the manufacturer says.

The main difference between pure sine wave and modified sine wave inverters is that the former produces a better and cleaner current. They’re more expensive, but for good reason.

In short, pure sine wave inverters are better suited to sensitive electrical or electronic items such as laptop computers, stereos, laser printers, certain specialized applications such as medical equipment.

Modified sine wave works well for most uses, and they’re more economical. If you mostly want to run lights, TV, microwave oven, tools, a modified sine wave inverter is fine for your needs.

The advantages of pure sine wave inverters:

a) Output voltage wave form is pure sine wave with very low harmonic distortion and clean power like utility-supplied electricity.

b) Inductive loads like microwave ovens and motors run faster, quieter and cooler with pure sine.

c) Pure sine wave reduces audible and electrical noise in fans, fluorescent lights, audio amplifiers, TV, Game consoles, Fax, and answering machines.

d) Pure sine wave prevents crashes in computers, weird print out, and glitches and noise in monitors.

e) Pure sine reliably powers the following devices that will normally not work with modified sine wave inverters:

  • Laser printers, photocopiers, magneto-optical hard drives
  • Certain laptop computers (you should check with your manufacturer)
  • Some fluorescent lights with electronic ballasts
  • Power tools employing "solid state" power or variable speed control
  • Some battery chargers for cordless tools
  • Some new furnaces and pellet stoves with microprocessor control
  • Digital clocks with radios
  • Sewing machines with speed/microprocessor control
  • X-10 home automation system
  • Medical equipment such as oxygen concentrators

What size inverter should I buy?

We carry many different sizes, and several brands of power inverters.

The size you choose depends on the watts (or amps) of what you want to run (find the power consumption by referring to the specification plate on the appliance or tool). We recommend you buy a larger model than you think you'll need (at least 10% to 20% more than your largest load).

Example: You want to power a computer with a 17" monitor, some lights, and a radio.

Computer: 300 W
2 – 60W lights: 120 W
Radio: 10 W
Total Needed: 430 W

For this application, you would minimally need a 500 W inverter, and should give some thought to a larger one, as there will likely be a time when you wish you'd bought a bigger model ... in this example, you might decide you'd like to run a fan while you compute, or let the kids watch TV.

Bear in mind also terms like Continuous Load and Starting (Peak) Load: You need to determine how much power your tool or appliance (or combination of them that you would use at the same time) requires to start up (starting load), and also the continued running requirements (continuous load).

What is meant by the terms "continuous-2000 watts" and "peak surge-4000 watts" is that some appliances or tools, such as ones with a motor, require an initial surge of power to start up ("starting load" or "peak load"). Once started, the tool or appliance requires less power to continue to operate ("continuous load")

What input voltage of the inverter i should choose? 12V or 24V?

If you are looking for an inverter for your 12V leisure battery in a motorhome, caravan or boat, there's not much choice in terms of the input voltage - you will need a 12V to 240V inverter, because your battery is 12V.

However, if you are building a standalone off-grid solar system (e.g. in a house, garden, shed or farm), then you can choose the voltage of your battery bank and the input voltage of an inverter accordingly.

Instead of a 12V battery bank you may choose to build a 24V battery bank (2x12V batteries wired in series will produce 24V). In this case you can use a 24V DC to 240V AC inverter, rather than 12V DC to 240V AC. This set up will give you some important benefits:

- The input current for the inverter will be 2 times smaller for the 24V than the 12V making the inverter and the entire system safer and more reliable

- Cables between your battery and the inverter do not have to be as thick as those used for a 12V battery bank and inverter.

This is particularly important for large standalone solar systems with 2000W inverters and for such power levels our recommendation is to opt for a 24V battery bank and an inverter with 24V input voltage.

Which s
olar system i should choose: on-grid or off-grid system?

On-grid means your solar system is tied to your local utility company’s system. This is what most residential homes will use because you are covered if your solar system under or over-produces in regard to your varying energy needs. All this means for you is that your utility system acts as your battery space. If you are producing more energy with your solar panels or system than you are using, the excess energy is sent to your grid’s power company, allowing you to build credit that you can cash out with at the end of the year, in a process called net metering. Being grid-tied is beneficial because you don’t have to buy an expensive battery back-up system to store any excess energy.

Being off-grid
means you are not connected in any way to your grid’s power system or utility company. This is appealing because you are 100% self-sustaining your energy use. However, there are disadvantages because off-grid systems require you to purchase back-up battery.

How do I connect two or more batteries?

It may be advisable to operate the inverter from a bank of 12 Volt batteries of the same type in a "parallel" configuration. Two such batteries will generate twice the amp/hours of a single battery; three batteries will generate three times the amp/hours, and so on. This will lengthen the time before your batteries will need to be recharged, giving you a longer time that you can run your appliances.

You can also connect 6 Volt batteries together in "series" configuration to double the voltage to 12 volts. Note that 6 Volt batteries must be connected in pairs.

12 Volt Batteries connected in Parallel to double the current (amp/hours)

6 Volt Batteries connected in Series to double the voltage to 12 Volts