Inverters. DC to 230 Volt AC
When you need 230 Volt AC on your boat, in the caravan, cabin or in any Off Grid battery installation, you must have converted your 12/24/48 Volt DC voltage to 230 Volt AC.
There are several things to consider and include in your calculation.
- First, you need to know how many watt, you need to pull at the same time, from your inverter. You should therefore know the maximum watt from the fridge, the radio, the fans, etc. if these potentially may run at the same time. You must put all these watt numbers together and you have the watt number that you should be able to extract from your inverter as an absolute minimum.
- You should also know the start currents as some, especially inductive loads (motors, pumps, etc.) may have much higher starting currents than those consumed when they are running. Therefore, it is also important to know how much power the inverter can deliver at startup moments and how long these moments last.
It’s usually not a problem when you buy a quality inverter and do not drive it to the limit. Always add min. 40% to the indicated startup current on your inductive loads.
MasterVolt is able to deliver up to twice the nominal wattage in short moments, and it often covers the need, but it always depends on your equipment and a calculation.
- You can pull all the 230 volt AC power from your battery bank via your inverter, but you need to make sure that there is enough power on the battery to deliver the amount of power needed and especially at the rate you need to consume it in .
Because it does not help to have a battery that contains all the power you need to use, if the power is needed suddenly and in large quantities. So your battery must be able to deliver at the speed you need. AGM and Lithium batteries are fast, while GEL can be a bit slow, (but normally GEL is a better choice than AGM), but read our battery guide to know more about the batteries.
- One very important thing is to look at the sinus curve that comes out of your inverter.
There are 2 different basic technologies used when converting 12/24/48 Volt DC to 230 volts AC
1. Modified its wave is the “old” method that delivers an almost square “sinus” curve to consumers. You should use this technology ONLY if you absolutely know that your consumers can handle to this type of “sinus” curve. As a rule, we do not use it today. Unless there will never be any other equipment connected than intended loads from the start (resistor load).
And if you do not know weather your equipment can handle to this, stay away from Modified sine waves.
2. True Sine wave is basically a fine rounded sine wave curve taken straight from the electrician’s basebook (see more further down).
This sine wave curve will work with all 230 Volt AC devices (provided the inverter can deliver the wattage).
From a good Pure Sine Wave inverter, there comes a sine wave that is even nicer than the one that comes from the grid.
With this sine type you made a good choice and I usually recommend it as a standard.
- Inverters with the modified sinus …. I would not recommend for anything but a resistance based load.
Pure sinus (or True Sine Wave) are many manufacturers calling their inverters. If you buy really cheap, you will not get anything but a modified sinus marketed as Pure Sine.
As the price rises, the sinus curves tends to be better and better, but don’t fool yourself. It’s the electrical items that you connect to the inverter that will pay the price if you have bought to cheap.
Clean resistive load consumers (motors, pumps, etc. are NOT resistive loads!) Are typically indifferent. But any kind of electronics are in the danger zone and depends on a pure sinus even when the load is high and the inverter’s ambient temperature is high. Even then the sinuses must be completely clean, because it does not take long to kill your sensitive equipment with bad sinuses.
We have chosen Mastervolt inverters, among other reasons, because even under peak load, they always deliver a pure sine wave curve that’s even nicer than the one you get from the grid.
Overload protection steps in before any bad sinuses may appear on your 230 Volt AC network.
- Temperature is important too. The inverter you are considering buying is usually data specified at 20 or 25 degrees ambient temperature. Unfortunately, this is usually not enough. From experience we know that the inverters are placed in the engine compartment, closed bench boxes or elsewhere where the temperature is often higher than standard room temperature. Therefore, the Mastervolt inverters are specified at a temperature of 40 degrees Celsius, and if 40 degrees are not enough, you must add 20% capacity, for every 10 degrees you exceed 40 degrees.
If you use the same rule of thumb on inverters specified at room temperature, you will need an inverter that is 40-50% larger in capacity, just to get to the side of what Mastervolt delivers by default …. ?
- Cables are always important! When working with DC supply to the inverter, there are always high amperage levels, so be sure to size your cables for it. Otherwise there may be a fire and it is not a thing to make jokes about.
Keep your inverter as close to the battery as possible. This will reduce power losses and reduce eventual EMC noise. If you can get the distance between the battery and the inverter down to 0.5 to 1 meter, it’s really good, but stay below 3 meters (if you need to go above 3 meters, just call us).
Under 3 meters you can use this rule of thumb: Amp/3 = Cable thickness in mm2 (square). So, a 2000 watt inverter (for 12 volts DC) that uses 167 amps (2000/12 = 167 amps) must have a 56 mm2 cable (167 amp / 3 = 56) and rounded UP to the nearest standard = 70 mm2.
- When working with 12/24/48 Volt DC, you are often allowed to do the whole installation yourself, it may not be advisable to do it, but you are probably allowed. However, do not make the 230 volt AC installations. This must be done by an authorized electrician.
You may connect extension cables to your 230V inverter if there is a standard plug in the inverter and connect your consumers that way. It is the same principle as if you were connected to the mains back home in the villa.
- When choosing your inverter, I would recommend you to be critical with the quality as this is the source of all your 230 Volt AC consumers.
Thus, electric noise from your inverter will propagate to your consumers and potentially make a humming/noise in your different consumers.
The quality is of course also a matter of how many years a given inverter will last before it’s worn out. Most manufacturers specify, as written above, at 20-25 degrees Celsius. This also applies to the expected lifetime. Again, Mastervolt are with their specifications at 40 degrees, a significantly better quality choice, than most others.
And what can it do? If you need to have your inverter in your boat or a mobile enviroment, choose an inverter that is marine approved (also for mobile installation) as it can withstand the shaking, the salt and moisture in the surrounding climate.
Qualitatively, you get what you pay for (sorry but that’s just how it often is ?) and if you need to have a solid power supply for years without trouble, no noise and ruined consumers. Do not save your money here.
It is the source of your entire 230 Volt AC net and all your consumers.
Now you may be able to figure out which inverter to use, but if you are in doubt, feel free to contact Energig and get our input. You can write to us here or call us at 70 500 999