Power Inverter

Inverter: converting direct current into alternating current

Not every power source is suitable for every electrical appliance. For example, solar panels generate direct current, for which standard household sockets are not designed. That is why you need to store the direct current in batteries and then convert it into alternating current using an inverter. This is the only way you can power your electrical appliances using solar energy or the supply battery in your motorhome.

Do you want to convert the power from your service battery into alternating current?  Then fraron.de is exactly the right place for you. In our inverter shop, you’ll find high-quality inverters for motorhomes with pure or modified sine wave output – so you’re sure to find the perfect model for your needs. Browse our range now! Our experts will be happy to advise you and help you choose the right inverter.

What is an inverter for a motorhome?

Inverters for motorhomes are also known as voltage converters or inverters: They convert the power from the supply battery into 230 volts. This allows you to use most standard household appliances in your caravan. If you choose a sufficiently large battery for your motorhome, combined with an inverter, your power supply is guaranteed. You can also charge the battery using solar power or via a charge booster whilst driving.

For this, I need an inverter in the motorhome – the voltage converter handles these functions

Thanks to the inverter, the 12-volt voltage is converted to 230 volts, so you get the same voltage as from a domestic power socket. 12 V to 230 V voltage converters are suitable for standard motorhomes. For specialist expedition motorhomes or truck-based motorhomes, which have an on-board voltage of 24 volts, there are 24 V to 230 V inverters.

Do you need more electrical equipment for your caravan? As well as our own-brand inverters and Victron Energy inverters, our range also includes charging equipment, DC/DC converters, power stations and other accessories.

Inverters and types of electricity

Pure sine wave or modified sine wave?

When it comes to inverters for motorhomes, a distinction is made between modified sine wave output and pure sine wave output. The former is usually referred to as a modified sine wave. This waveform mimics a sine wave in a stepped pattern, which is why it is more suitable for simple 230 V appliances.

Pure sine wave power, on the other hand, uses a clean sine wave and is therefore also suitable for powering capacitive devices, appliances with built-in electronics such as fully automatic coffee machines, or battery chargers for e-bikes. With these models, the pure sine wave ensures trouble-free operation. However, if you only intend to use very simple appliances such as kettles, toasters or fan heaters whilst on the move, a sine-wave-like voltage is generally sufficient. You must, however, take care not to connect any sensitive devices with high-quality electronics to it.

In short: inverters with a sine-wave-like output, also known as trapezoidal inverters or modified sine wave inverters, are suitable for simple filter coffee machines, fan heaters, hairdryers and light bulbs, whereas a pure sine wave inverter can be used to power electric toothbrushes, laptop power adapters, high-quality coffee machines or induction hobs.

Can the voltage converter for the motorhome be powered by solar energy?

You have the option of charging the battery that supplies power to the inverter using a solar panel system, as solar panels and charged batteries both supply direct current, whilst standard electrical appliances require alternating current. The voltage converter then simply converts the direct current into alternating current at the required 230 volts.

What inverter capacity?

When choosing the right size for your sine wave inverter, you must take into account the 230 V loads to be connected to it and the available battery capacity. The 230 V load with the highest power rating, or the total power of all loads connected at the same time, determines the inverter’s power rating. Smaller 300-watt sine-wave inverters are suitable for charging small electrical devices such as cameras, mobile phones or laptops. To charge one or two e-bike batteries, you should choose a 650-watt inverter. The most common inverters are sine-wave voltage converters up to 1200 watts, which allow you to power the 230-volt appliances mentioned above, as well as a filter coffee machine (usually around 800 watts) or a toaster. If you opt for a large inverter rated at 1500 watts or more, you can use fully automatic coffee machines, hairdryers and vacuum cleaners without any problems. When choosing an inverter for your motorhome, you should always allow for a margin in case you need to add more appliances.

The amount of electricity an inverter draws from the battery (or batteries) depends on the power consumption of the devices connected to it. You can roughly calculate the current draw of the inverter by dividing the power of the connected 230 V load by 10 for a 12 V inverter and by 20 for a 24 V inverter. A 1,500 W fan heater therefore draws approx. 150 A from a 12 V battery or 75 A from a 24 V battery.

The existing power supply batteries must be capable of supplying this current, as we will discuss below.

How do I find the right inverter for my motorhome?

Voltage converters are available in various power ratings, ranging from a few watts to several kilowatts, with a distinction made between continuous power and peak power. The peak power is only available for a short period of time and is measured in watts. A mobile phone requires around 5 watts, whilst a tablet charger requires around 15 watts. If you want to connect a laptop power supply, you should expect it to draw between 100 and 200 watts. An electric kettle draws between 1000 and 1500 watts.

To choose the right inverter for your motorhome, start by making a list of all the appliances you want to connect in your motorhome. You’ll always find the power ratings of the appliances on the type plate. Check the maximum power rating. That way, you’ll be on the safe side.

It is best to allow for a safety margin of 20 to 30 per cent so that you can connect an additional device if necessary without having to buy a new voltage transformer. This ensures that the inverter is not overloaded.

These loads act on the motorhome’s inverter

Various types of load can be applied to the voltage converter in a motorhome – a distinction is made between resistive, inductive and capacitive loads.

Devices that operate with resistive loads – i.e. those that convert the supplied energy entirely into useful power – include, for example, simple incandescent bulbs or fan heaters. In such cases, the inverter output can be designed to be almost exactly the same as the load power. A 1000-W inverter is sufficient for a 900-W fan heater.

Inductive loads, on the other hand, require a high inrush current, which can be 3 to 10 times the specified rated power, depending on the appliance. This applies to all types of appliances with electric motors, such as fridges, air conditioners, compressors and pumps. The inverter for the motorhome must therefore be designed with sufficient reserves or a corresponding peak power rating. A 60W compressor fridge requires a 600W inverter to supply the compressor’s starting current.

In addition, there are capacitive loads that place the highest demands on the supply voltage. For these loads, you always need models with a pure sine wave voltage. This applies, for example, to electric toothbrushes, which are charged capacitively.

Grid priority control

A mains priority circuit is also a practical solution, as it detects when a second power source, such as shore power from a campsite, is connected. The inverter output is then automatically disconnected from the on-board power supply and the shore power takes priority; in other words, at that moment all sockets are powered by shore power and the inverter can be paused.

Inverter for motorhomes with remote control

Some voltage converter models come with a handy remote control for switching them on and off. This is connected via a socket on the inverter. As long as the motorhome’s inverter is switched on, it consumes power even if no active loads are connected. To avoid this self-consumption, the inverter should always be switched off when it is not in use. When the voltage converter is switched off using the remote control, only a small current of a few milliamps flows to enable communication between the remote control and the inverter. The remote controls usually have a practical cable length of 5 metres. Alternatively, there are also some smart models with Bluetooth functionality, allowing the inverter to be operated via an app.

Which inverter for which battery – these combinations are compatible

The type of battery or batteries you need for your voltage converter in your motorhome depends on how you intend to use it. You need to take into account the inverter’s maximum current draw and the duration of power consumption.

The two types of battery used in conjunction with inverters in caravans, motorhomes or boats are, on the one hand, conventional lead-acid batteries (flooded, GEL, AGM) and, on the other hand, modern lithium batteries.

Both types of battery are generally suitable for the products in our inverter shop, although lithium batteries offer many advantages. Some of these are listed below:

• Weight: Lithium batteries weigh about half as much for the same capacity
• Usable capacity: With a lithium battery, 80 to 90% of the energy can be drawn without adversely affecting its service life. With conventional batteries, however, this figure is only 50%.
• Suitable for fast charging: Lithium batteries can be charged without any problems at a charge current of 50% of their capacity, whereas conventional batteries can only be charged at 20 to 30%.

When determining the required battery capacity for use with an inverter, the discharge current and the discharge duration are both important factors. A 1400-watt coffee pod machine requires a large inverter with a minimum output of 1500 watts and draws a current of 140 amps from the 12V battery – but only for a period of approximately 2 minutes. To deliver this high discharge current, a conventional battery must have a capacity of at least 150 to 180 Ah. With lithium batteries, 100 Ah is usually sufficient, provided the battery is equipped with a 150A battery management system (BMS). The energy drawn from the battery is relatively low (approx. 4A), as the coffee brewing process, including the heating phase, takes only 2 minutes.

The situation is different for a consumer that draws power over a longer period of time. If an empty 500W e-bike battery is to be charged, this requires approximately 50 Ah of battery capacity (including conversion losses). A small 350–600 W inverter in the motorhome is sufficient for this purpose. If the vehicle is equipped with only a standard 95 Ah auxiliary battery, this will be a tight squeeze, as this battery will already be more than 50 % discharged after charging the e-bike battery, which corresponds to the maximum recommended usable capacity. With a lithium battery of the same capacity, there would still be a usable residual capacity of 30–40 Ah remaining.

Buying an inverter for your motorhome – what you should look out for

To find the right inverter for your motorhome, add up all the devices you want to power at the same time, e.g. a laptop, a lamp, a television. Then calculate the total power consumption of all appliances that require a high inrush current, such as fan heaters, and include this high inrush and start-up current in the overall calculation. We are happy to assist you in selecting the correct voltage converter.

We also offer combination units comprising an inverter, charger and grid priority circuit, which are becoming increasingly popular in motorhomes. Our own-brand inverters and Victron Energy inverters are usually available for immediate delivery.

Have the voltage converter for your motorhome fitted by a professional

As with all our products, you can have your motorhome inverter installed by our experts. Simply get in touch with us and we’ll work with you to identify your requirements and assess which model is best suited to your needs. We can advise you on the full range of components and assist you with the planning. Please use our enquiry form – we look forward to hearing from you!

Frequently Asked Questions about Inverters (FAQ)