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Buying a power inverter for your campervan – A to Z guide

If you own a campervan then at some point you’ve probably thought about buying a power inverter. You might think that once you have a power inverter fitted in your campervan that you can just plug in any mains powered 230V device you like, just as if you were at home. Unfortunately, it’s not quite that simple.

In this article, we aim to help you better understand the basics of this technology, so you can decide whether you actually need a power inverter for your campervan, and if you do, which type you should buy.

Does your campervan really need a power inverter?

The first question you need to ask yourself, is what do you need a power inverter for? There may be alternative more efficient and cheaper ways to run and charge your devices. For instance, using your vehicles 12V system can be an effective way to charge a mobile phone or tablet computer, all you need is a simple and inexpensive 12V USB charger that plugs directly into a cigarette lighter type socket.

 

What about charging a laptop?

Generally speaking, a power inverter will be needed to run and charge a laptop. However, it’s not the only way; there are 12V universal laptop chargers available. If the only reason you’re considering buying a power inverter is to charge a laptop, then a 12V universal charger may be worth considering as an alternative to an inverter.

A point worth considering: a power inverter can also be used to run other devices too, so is going to be more versatile than a (single purpose use) laptop charger.

 

What about running a TV?

Well, if want to use a 230V mains TV and you’re not connected to mains hook-up, then yes, you would need a power inverter. However, it would make more sense and be far more energy efficient to use a 12V TV in the first place. They generally use less power and can plug directly into your campervans 12V DC power source.

Take a look at our article on Campervan TV Systems.

 

What about using a microwave?

Yes, when not connected to EHU (electric hook up) you’ll definitely need a power inverter to run a 230V microwave off of a 12V DC power supply. Here are a couple of important points to consider when choosing a power inverter.

  • The input power required to run a microwave oven is considerably higher than the output power. For example, a 700 watt microwave will actually draw around 1200 watts of power.
  • Not all power inverters are suitable for running microwave ovens. Most modified sine power inverters will not run a microwave oven, whereas a pure sine wave inverter will.

This pure sine power inverter is suitable for running a microwave.

Also, check out our Best Campervan Microwave article for help in choosing the right microwave.

 

Using other power hungry devices:

It may be tempting to use a 230V electric kettle, hair dryer or electric heater, but like a microwave oven these too use a lot of power and will very quickly drain your campervan’s leisure battery if used regularly through a power inverter. As an example, a standard 2000 watt electric kettle would completely flatten an 85 amp hour leisure battery in about half an hour. (As a rule, a leisure battery shouldn’t be discharged below 40% on a regular basis, doing so will damage the battery.)

Installing an inverter and upgrading the 12V system to cope with high power demand is going to be expensive and will still only give you a limited amount of usable power. You’ll also have the problem of recharging the batteries. If you really do need to use power-hungry mains appliances off grid, then in my opinion, a generator would be a much better option. And don’t even bother with an electric kettle, just use your gas burner to make a cuppa.

 

There are two main types of power inverters?

Pure sine

A pure sine power inverter produces an AC current that is the same smooth, clean flow as the electricity supply at home. This means that (in theory) any mains appliance you use at home can also be used through a pure sine wave power inverter. This convenience does come at a cost however, as pure sine power inverters are more expensive to buy than modified sine wave inverters.

 

Modified sine

A modified sine wave power inverter will power most but not all electrical appliances. A modified sine inverter will run lighting, power tools, other devices with electric motors, and may power a low wattage basic manual microwave oven (although I have read that some people have struggled with this). Also, some interference may be experienced when using a modified sine power inverter to power 230V TVs, audio equipment and computers. Modified sine wave power inverters are cheaper to buy than a pure sine wave inverter.

 

Which one should you buy, pure or modified?

For running a laptop, charging mobile phones and digital cameras, powering lights, portable drills and maybe some non-digital microwave ovens, a modified sine power inverter should be fine. However, to be 100% sure that a device will work correctly (and if you can afford the additional outlay) then buying a pure sine wave power inverter will ensure that pretty much any mains device you use at home (which is within the continuous power range of the inverter) will work as intended.

 

How to choose the correct wattage power inverter

First, you need to know how much input power (wattage) collectively your devices use. Each device should have this information printed on it somewhere. So, for example:

  • Mobile phone charger – 5 watts
  • Laptop – 25 watts
  • Small TV – 70W
  • 700 watt microwave oven  – 1200 watts input power
  • Total amount 1900 watts

Now the total amount shown above is based on all the devices being used at the same time (this is not recommended). It also takes into account the input power of the microwave (1200 watts) as this is the actual amount that a 700 watt microwave uses.

To make sure that the power inverter can supply the total amount needed in the example above, it would need a continuous power output of at least 2,185 watts. This includes an additional 15% just to give a little wiggle room.

If you just wanted to use the power inverter to run the microwave, then an inverter that outputted at least 1380 watts (1200 watt microwave input power, plus 15%) would be required.

 

Peak and continuous power ratings

The peak power rating (surge) of an inverter is the maximum amount of power the inverter can deliver over a short period of time. Some devices such as a compressor fridge use a higher amount of electricity when they start up. This surge then drops once the appliance is running.

The continuous rating is the amount the power inverter will continuously deliver after the initial surge (peak power).

 

What size battery do you need and how long will it last?

There is no point in buying a large power inverter if your leisure battery can’t handle the demands. So you need to work out how much current (amps) is going to be drawn from the battery by your devices. To do this, simply divide the total amount of watts needed by 10.

 

*For example: if all your devices collectively use 1000 watts then your battery/batteries will need to supply 100 amps.

 

Converting 12V DC current to 230V AC current is a pretty inefficient process. The calculation above factors in this inefficiency (loss of energy) into the final figure.

 

How long your battery/batteries can deliver this load will depend on two things.

The size (Ah – amp hours), and the overall condition. Say you have two 110 Ah batteries (220 Ah in total) and using the example above*, the total amount of current drawn is 100 amps. You then divide 220 x 100, which is just over 2 hours (2.1 to be precise).

Now you wouldn’t want to completely run down your batteries as this could damage them. It is recommended that in order to keep a leisure battery in good condition it is not regularly discharged below 40%. So with this in mind, two 110 Ah batteries would give approximately 1 hour 25 minutes of useable power.

 

Buy a power inverter that will protect your battery from being fully discharged.

A good quality power inverter will sound an alarm when the battery is running low. If this continues, the power inverter will then turn itself off. However if the on switch on the front of the unit remains turned on, then a power inverter will still continue to draw a small amount of current even with nothing connected to it. So always make sure it is turned off when it’s not needed, to prevent your battery from going completely flat.

 

Is your leisure battery up to the job?

If you intend to draw a large amount of power through the power inverter for more than a few minutes at a time, then you’re going to need a very robust 12V system. This will include suitable heavy duty cabling (from the power inverter to the battery) and you’ll also need more than one large Ah (amp hour) leisure battery installed. Obviously, the power drawn from the leisure battery will need to be replenished. This can be done via the campervan’s alternator whilst you’re on the move, or by using solar energy.

We have an article on Campervan Solar Panels.

 

Warning:

  • If you drain your leisure battery too much and too often it may not be able to recover.
  • Do not connect a high wattage power inverter to your vehicle’s starter battery. Starter batteries are designed to produce a large amount of current in a short burst, whereas a deep cycle leisure battery is designed to deliver a more consistent flow of current over a longer period of time.
  • Make sure that your leisure battery is in good condition, or it may not be able to cope with the demands of a power inverter.

Two power inverters suitable for a campervan

Pure Sine Wave Power Inverter

2000 watt 12V DC to 230V/240V AC pure sine wave power inverter

As explained earlier in this article, the output power produced by a pure sine power inverter is the same as a domestic electricity supply. Therefore a pure sine wave inverter is compatible with a much wider range of mains appliances, such as microwave ovens, TVs, audio equipment and computers. This 2000 watt pure sine power inverter offered for sale on Amazon by Photonic Universe Ltd, converts a 12V DC power supply into 230V – 240V AC mains power. The inverter has a continuous power rating of 2000 watts with a peak rating of 4000 watts.

The power inverter has two UK 3 pin sockets on the front, as well as a standard USB port for charging devices like mobile phones or tablet computers.

Installation is very straightforward and the cables needed to connect the inverter to your leisure battery are supplied.

The unit has a low battery alarm feature; meaning that an alarm will sound if the battery is running low. If the power demands on the battery continue, then the unit will automatically shut down to prevent the battery from being fully discharged as this could result in damage to the battery.

Note: Always make sure that an inverter is turned off when it’s not being used, or it will continue to draw a small current and flatten the battery.

The physical size of the inverter is 40 cm x 22 cm x 9 cm.


Modified Sine Wave Power Inverter

1500 watt 12V DC to 230V/240V AC modified sine power inverter 

This 12V DC to 230V – 240V AC modified sine wave power inverter from ERAYAK  and availiable on Amazon, offers an affordable solution to off-grid mains power. It will power electrical devices such as game consoles, electric shavers, digital cameras, camping lamps, power tools and laptop computers. On the front of the inverter are two 3 pin UK plug sockets and a 2.1 amp USB port which is ideal for charging mobile phones and tablet computers.

The ERAYAK modified sine inverter is available in 5 sizes, 500W, 600W, 1000W, 1500W and 2000W.  The one we are covering here is the 1500 watt version, which has a continuous power output rating of 1500 watt and peak power output rating of 3000 watts. The unit has a high and low voltage shut down function to protect the leisure battery. There are also 6 internal fuses to protect your devices.

The case of the inverter is made from lightweight but strong aluminium, with two quiet running cooling fans at the back. The ERAYAK inverter is easy to install and the appropriate sized positive, negative and earth cables are included with the unit.

Note: This type of power inverter is not compatible with air conditioning units, refrigerators or microwave ovens.

The physical size of the inverter is: 26.5 cm x 16.7 cm x 7 cm.


Installing a power inverter

When installing a power inverter (especially high watt inverters) locate the inverter as close to the battery as possible. Connect the inverter to the battery using short, suitably rated cables. It’s also a good idea to install an inline fuse and an easy to reach, remote on-off switch, if the one on the unit is not easily accessed.

Warning: Always connect large wattage power inverters directly to the leisure battery. Do not use your vehicle’s 12V cigarette lighter type socket. These type of sockets are not designed to handle high loads.

Here’s a video showing how to correctly connect a 2000 watt inverter to a leisure battery.


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