Purpose and main usage scenarios of inverter

Let’s go today to find out what an inverter is, which one to choose to best meet our needs and how it works. It is in fact a very important accessory for many of us, especially for those who love to go free and do not want to depend on the presence and availability of electric columns while traveling.

What does an inverter do? The entire system of the camper is in direct current at 12V, and the 220V sockets that you find inside your vehicle work if and only if you are connected to the electricity column of the parking / camping / storage area.

Long story short, these sockets DO NOT work if you are free parking.

But it is they who make it possible to use some small and large appliances that we are used to using when we are at home and which we do not want to give up when we are away with the camper.

The hairdryer, or even more frequently the coffee machine or the air conditioner. When we talk about the coffee machine we do not mean the mocha of course, but the one that works with the pods.

If we love to take a break, do we have to give up, for example, the pleasure of drinking a coffee like at the bar even on our camper?

Not necessarily, because this is the job of an inverter.

In fact, the inverter works to transform the 12V direct current of the battery into 220V alternating current, therefore suitable for the operation of our appliances.

For this to happen, two cables with a large diameter are needed to connect the service battery to the inverter itself. We will then have to connect our appliances to the inverter by simply inserting the plug when necessary.

Energy Is Not Unlimited: What Problems Are Created

Everything seems simple and straightforward, but that’s not exactly the case.

A first problem is in fact given by the fact that the current inside our service battery is certainly not unlimited, quite the contrary.

And a device, albeit apparently small as a coffee machine, drains such an amount that your battery will be able to withstand, to be optimistic, for about twenty minutes at the most.

Of course, twenty minutes are more than enough to make a good coffee, but what would happen if we instead connected the air conditioner to the inverter? It would happen that twenty minutes of fresh air would certainly not be enough for you. So let’s try to understand how to solve the problem.

Which Batteries and Which Inverter to Choose? An important first step is to use service batteries that are able to handle high discharge currents at the start.

Lithium RV batteries can therefore be a good solution, because unlike AGMs they are able to handle higher discharges, even of 100A.

However, keep in mind that batteries do not like to be continuously discharged and charged, and above all they do not tolerate the transformation of their current from direct to alternating well.

They face stressful situations, and can therefore spoil prematurely.

Then you need a suitable inverter: the best you can find is inverter pure sine wave.

What do I need a 12V or 24V inverter for?

An inverter is always used when a power source (battery or PV system) supplies direct current, but the electrical devices used require alternating current for operation. Since most electrical household appliances are designed for alternating current from the 230 V socket, you need an inverter to operate them with a solar system. The PV inverters convert the system’s direct current into alternating current at 230 V.

Where can I use an inverter?

You need an inverter, also known as an inverter, if there is no socket available for the electrical devices. Modern inverters are used here, among other things:

• In cars
• In mobile homes
• On boats
• In photovoltaic systems
• In garden houses

For photovoltaics (PV) you always need an inverter: The solar modules of the PV system generate direct current and charge the battery, which in turn is connected to the inverter and enables the operation of the 230 volt devices. You can connect a wide variety of devices to the system, whereby the required power must be taken into account.

What is a motorhome inverter?

In the mobile home, the solar inverter enables the operation of televisions, laptops, coffee machines and other 230V household appliances. To do this, it is connected to the supply battery for mobile homes and has an integrated mains plug. Some also have a USB port for easy charging of smartphones and other devices.

Where do I mount the PV inverter?

For best performance, you should mount the inverter in a cool place. The device is usually installed near the floor, so there are wired remote controls for convenient operation.

What is the difference between direct current and alternating current?

With direct current, the direction and strength of the current are always the same. With alternating current, the direction of the current and the amount of charge being moved are constantly changing. At an alternating current frequency of 50 Hertz, the current changes its polarity 50 times per second, while the polarity of direct current remains constant over time.

While direct current can only be transported sensibly over short distances without high energy losses, alternating current can be transported over hundreds of kilometers with almost no losses.

How do inverters work?

The main task of the inverter is to convert the battery direct current into 230V alternating current. Brand manufacturers such as ECTIVE, DOMETIC and Renogy Energy offer PV inverters with a pure or modified sine wave that impress with their high level of efficiency. The purchase decision depends on the requirements of the connected consumers. Sensitive consumers only work with pure sine wave alternating current.

Modified sine wave inverter

Modified sine wave inverters mimic classic household electricity, the sine wave is also known as trapezoidal or staircase. The simple battery inverters are cheaper in price because no complex smoothing technology is used. The devices are the right choice for simple consumers such as coffee machines, but they are not suitable for operating LEDs and energy-saving lamps. You can use these inverters in combination with a PV system as an inexpensive photovoltaic inverter.

Pure sine wave inverter

Pure sine wave inverters are equivalent to household electricity. Many modern electrical devices require this pure sine wave voltage for proper operation. This includes, among other things, modern entertainment electronics.

Whether an electrical device has to be operated with a pure sine wave is usually not apparent from the outside. To be on the safe side, we recommend purchasing a higher quality sine wave inverter. This means that all electrical devices work without restrictions.

Compared to the cheap inverters with a modified sine wave, the devices with a pure sine wave are heavier and more expensive to buy. They work excellently with a solar system and, depending on the model, have practical additional functions.

Buying guide: inverters for solar systems

When you buy solar inverters, the offer ranges from inexpensive inverters with a modified sine wave to top models with a pure sine wave and numerous additional functions.

While some electronics will work with the modified sine wave, you can be safe by purchasing a pure sine wave model. This means that any connected 230V device can be operated in any case.

Another important criterion when purchasing is the output power provided. How much power an electrical device requires is usually printed on the device and given in watts. If you want to run several devices at the same time, you have to add up the power values. The possible continuous output of the solar inverters offered is between a meager 150 watts and up to 3,000 watts.

Important: When switching on most electrical devices, significantly higher currents occur for a short time, which can be 5 to 10 times higher than the continuous output. Drills and electric saws, for example, have very high starting currents. Therefore, plan for power reserves.

Rule of thumb for calculating the required power

To ensure that the inverter also absorbs the current peaks and that sufficient power is available at all times, simply use the following rules of thumb:

• Calculate a reserve of 3 to 4 times the continuous power for devices with an electric motor.
• For all other consumers, a power reserve of 1.5 times the continuous power requirement is sufficient.

Tip: Switch on the loads one after the other and always switch on the most power-hungry load first. Do not switch on all devices at the same time via a multiple socket.

Further selection criteria and equipment of the inverters

Many modern inverters integrate practical additional functions that improve and simplify the operation of a photovoltaic system.

With MPPT solar charge controller for off-grid systems:

In connection with photovoltaics and a stand-alone system, it is worth buying a PV inverter with a built-in MPPT solar charge controller. With such a device, you save yourself the investment in a separate solar charge controller. Also pay attention to the PV power of the PV modules.

With NVS and UPS function:

In addition, an NVS and UPS function can increase the area of ​​application. When operating as an uninterruptible power supply (UPS), the available mains power is given priority and, if it fails, it automatically switches to battery operation.

Available for different output voltages:

Most models have an output voltage of 12 V to 230 V, the charging voltage is 10.5 to 14.4 V. Alternatively, there are devices with a voltage of 24 V to 230 V, with these the charging voltage is between 21 and 28, 8 V. Also make sure that the efficiency is as high as possible.

How long do PV inverters last?

These integrate numerous safety functions to protect the connected loads and the inverter. This includes features such as:

• Overload protection with automatic shutdown
• overheat protection
• Overvoltage protection
• undervoltage protection
• reverse polarity protection

Thanks to these protective mechanisms, inverters last for many years.

What does an inverter cost?

Inexpensive models produce a modified sine wave and offer low wattage. Top models with a pure sine curve cost significantly more, and devices with more power and additional equipment such as NVS and UPS functions are more expensive. The advantage of buying such top-of-the-line inverters is that you save on purchasing a separate UPS device.

What do I need for a self-sufficient and sustainable power supply with photovoltaics?

You can implement the self-sufficient power supply in the form of a solar stand-alone system that is not connected to the public power grid with the following components:

• Solar panel generator,
• Solar charge controller for charging the supply battery,
• Inverter for solar to convert the direct current of the battery into alternating current for the connected electronic devices

Note: There are also inverters with an integrated solar charge controller!

How many inverters do I need per kW?

You select the inverter according to the rated output. With an output of 5 kW, the nominal DC output of the inverter should also be 5,000 watts, i.e. 5.0 kW. With higher output of the solar modules, two or more inverters are required accordingly.

Practical accessories for PV inverters

The inverters for solar and the self-sufficient power grid can be operated even more conveniently with the right accessories. With a wired remote control, you can turn the device on and off from a distance, read the charge and see the battery level at a glance. Battery cable sets and fuses for inverters are available for the internal wiring of devices.