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Why would you need an inverter in your vehicle?

Why would you need an inverter?


The mains electricity supply that runs your appliances at home requires a 240 volts AC (Alternating Current) supply. Automotive batteries supply a much lower voltage (mostly 12 volts or some are 24 volts) DC (Direct Current). An inverter converts 12 (or 24) volts DC to 240 volts AC, allowing home appliances including phone chargers, computers/laptops, TVs, coffee machines, Etc to be run in recreational applications such as 4WDs, caravans, camper vans/trailers or boats Etc. This means you can still have some of your home comforts while you are “off grid” whether you are camping, enjoying the great outdoors, or simply getting away from it all.


If you want to run 240V appliances from an inverter, the first thing to do is to choose a suitable size inverter. The second thing is to choose a suitable size battery bank to run the inverter. The easier part is choosing a suitably sized inverter. This will depend on how much 240 volt power you need and this will be determined by what appliance(s) you want to run. Required supply power is normally specified on a Compliance Plate on the back of an appliance and this is the important figure to go by. 


Some power calculations are not straightforward, for example:


  • Similar to power tool battery chargers, some variable power appliances such as phase controlled variable speed power tools as well as appliances with half wave power control can draw very high peak current, also requiring larger inverters than suggested by their stated power rating.
  • The power of a microwave means the rated (or “cooking”) power. The electrical power consumed by the microwave will be much higher than the rated power, so to run a microwave you should choose an inverter based on the figure on the compliance plate rather than the cooking power label on the front.
  • Some power tool battery chargers may appear to have a relatively low Average Power consumption, but have a very high “Peak Power” need. E.g. a 200W charger may require a 700 Watt or even 1000 Watt inverter to cover the “Peak” current.


In most cases, you will only be able to run one high power appliance at a time, so for example, trying to run a kettle and a toaster at the same time is likely to result in inverter shutdown and/or over-worked batteries and/or cables. Please see REDARC's handy guide showing suggested inverters for various appliances.


The more difficult part is choosing a suitably sized battery bank. This will depend on how long you want to run the appliance(s). This is further complicated by the peculiar ways various battery types charge and discharge.


A high power appliance (such as an air conditioner) running for a long time (such as all day or night) will require a very large battery bank and may not be practical.


A low power appliance running for a short time will only require a smaller battery bank.


Once you have determined your required inverter size and battery size, the remaining important factor is to get the installation right.


You must use the recommended cable and fuse types/sizes and that all joints and connections are sound and suitably rated. Cables that are too long and/or thin will have too much voltage drop, resulting in premature shutdown of the inverter and/ or overheating of the cables/fuse-holders/connections. Taking shortcuts on installation will lead to unsatisfactory appliance performance and frustration instead of an enjoyable camping holiday.


Want to know what inverter you'll need to run your appliances on the road?


Download REDARC's inverter selection guide here.


 Although it is powered from a 12 volt battery, 240 volts from even the smallest inverter can be as dangerous as 240 volts from a mains socket at home and must be treated with due respect.