And already the problems begin:

There are hundreds of them on the market with extremely different prices. Now you might say: If you buy cheap, you buy twice, and that may be true, but that doesn’t mean that I’m best off with the most expensive one. So what to do?

To find the right inverter you need to know 2 things:

• How many watts do my devices have? And which devices are running at the same time?
• Which types of devices do I want to use?

The first question is important because I figure out what power the inverter must have. If I have a 2000W oven and it should always run in the morning together with the 1800 Watt coffee machine, that is 3800 Watts. sounds simple at first, if there were not the inrush currents. Inrush currents are only present for a very short time, but can be many times higher than the continuous current that flows afterwards.
(This is called the inductive loads, which includes pretty much everything with a motor/drive. E.g. drilling machines, washing machines but also compressors, etc.)
However, the manufacturer of the devices always specifies the power in relation to the continuous current and not to the inrush current. A rule of thumb says that you should always calculate with twice the current. In our example, that would be 7600 watts. Fortunately, the inverters also have a tolerance and always indicate two powers. On the one hand, of course, the continuous power but also the short-term power. This should be but is not always located at twice the continuous power. And it is usually only available for a few milliseconds, which is difficult when the connected motor needs e.g. 5 seconds to reach full speed.

The second question: device types? Now we come to the sine curve. I think that everyone has seen such a curve before and if not, it doesn’t matter because one is shown below. But what does this have to do with inverters? Well the cheap inverters have a so called modified sine wave and that means simplified that the curve is actually not a curve but more like a staircase. And exactly these modified sine curves are not tolerated by every device.

Which device needs which sine wave now?
So-called capacitive loads.
This usually includes all sensitive electronics, such as the coffee pad machine and the fully automatic coffee machine, control units, measurement technology, amplifiers, hi-fi systems, etc.
Some of it can still work but it can lead to premature defects, unpleasant side effects like humming and other side effects that you don’t want to have.
And how do I find out if my device can handle a modified sine wave? This is usually only possible by trial and error, because the manufacturers usually do not provide any information.

So if I just want to run a classic coffee maker and some chargers, then an inverter with a modified sine wave may be quite sufficient but…

my conclusion:

An inverter I will buyonly once for a very long time. For this reason, I advise the following:

1. required total power plus 30 percent reserve
2. real sine wave to be future-proof, because nothing would be more annoying if you buy a new device a few months later and find out that it can’t cope with a modified sine wave.
3. double peak load (3000/6000W: even if this is only in the millisecond range, it usually means that instead of 3000 watts of continuous power, you can also call up 3500 watts over a few minutes).
4. In the end, all of the above has an impact on the price, which in my eyes is amortized very quickly if you convert this to the years of operation.

And last but not least, here’s the model I’m planning to install:

Giandel 3000 Watt pure sine wave*

* The links are so called affiliate links. This is a fair way to support me and say thank you, because it costs you nothing except the regular price of the item and I get a commission for your purchase which helps me to realize this project and the following.

Here is on the one hand the inverter and on the other hand the direct connection to the shore power.

Which power I give priority to depends on the planning.

In the first step you can say that I don’t need the Wechserlrichter when the shore power is connected. This would mean that the shore power is preferred to the inverter.

In the example above the charger is supplied parallel to the total 230V demand of the CamperVan, which charges the battery(ies), because the battery(ies) still supply the 12V grid and also the inverter.

If you want to connect a generator to charge the battery, a switch should be installed in the supply line to the relay for the mains priority circuit, as very few generators can supply enough power to maintain full 230V operation during charging. But even if this were the case, it would only prolong the charging process unnecessarily and thus also the noise pollution caused by the generator.

By the way, the picture shows the mains priority switch of the company offgridtec* which I plan to use

* The links are so called affiliate links. This is a fair way to support me and say thank you, because it costs you nothing except the regular price of the item and I get a commission for your purchase which helps me to realize this project and the following.

1. Option: Of course the alternator. This charges the starter battery and can of course also charge the body battery. In the simplest case this requires a cut-off relay and in the special case a charging booster. When is this special case? I will write a separate article on this topic at some point.
2. Option: The charger on shore power. In my case of application this is only an emergency solution, because I plan to be self-sufficient and therefore I will have shore power available rather rarely.
3. Option: Solar. Nowadays the dimensioning and the costs are rather standard but still very individual. In my case it will be the main source of supply and therefore I will dedicate one or more own contributions to this topic.
4. Option: The Generator. It replaces the shore power connection and supplies a charger. Also this can only be an emergency solution, because whether I run the van motor or a generator is at most a difference in the resulting noise pollution for the surrounding area. So this is only possible if you are not only self-sufficient but also lonely.

The options mentioned are of course not exclusive and so you don’t have to choose one but can combine them. For this reason all 4 of them are planned. The generator does not appear in the plan, because it only supplies the shore power connection if necessary.

And now an important warning and an explanation!
Work on the electrical system is life-threatening and must be carried out by a specialist. You neither want your WoMo to burn down nor do you want to get an electric shock. So only do it yourself, if you know what you are doing! My plans are for me and can contain mistakes, so I don’t take any warranty or liability for them.

The following plan shows only the electric circuit. So the drawn lines are not necessarily single-core. The lamp symbol is only a symbol for a power consumer to make the plan easier to understand. Whether this is a lamp or a consumer connected to a socket is not important for the plan.
But again: Who does not understand the plan must get itself compellingly technical support, in order to avoid damage to humans and machine.

The idea:

What do you see there now?
There are 3 potential power sources (shore power, solar, alternator) These all need their own electronically controlled connection to the batteries.
-The cut-off relay or charge booster connects the starter battery to the body battery. (in both directions)
-The solar regulator converts the voltage to 12V and conducts/regulates the charging current to the battery.
-The 230V charger does what the name says when shore power is available.
-Then you can see a grid priority circuit in the plan. This relay only controls a “preferred” power source. In this plan this is the shore power (A). If this is present, the inverter is disconnected. But I will write a more detailed report about this as well, because this variant has advantages and disadvantages and might be adapted again.

The voltmeters only show the voltage of the respective batteries. This is purely informative and optional.

The battery monitor shows, depending on the version, everything concerning the battery. Voltage, capacity, charge current, discharge current, consumption, remaining range, etc. Although this is also an optional accessory, because it does not serve the function, I can only warmly recommend it, because this is the only way to get an overview of your energy balance. Of course, you could always measure everything manually and calculate the values yourself but economy is different.

Now the power sources and batteries are under control. So we can take care of the consumers.
For this purpose we need a 12V connection panel, which also houses the fuses and an inverter which converts the 12V DC voltage into 230V AC voltage. From the inverter on, we continue in principle according to the rules of home electrics with a few exceptions. You already suspect it? There is also a separate contribution to this.

How I have connected what is of course still detailed in the individual articles that show the actual conversion. The planning phase is still running. Of course, the material list is also part of the planning. In the range of the devices one can get everything from cheap to expensive or from simple to luxury. What it will be in the end is of course budget and wish dependent.

But a warning in advance! I will order large parts of this equipment directly in China, because there it is mostly produced anyway. BUT do this only if you know how the Chinese mail order companies tick. There “label fraud” is the order of the day. PWM chargers are often called MPPT chargers. Solar panels have 300 Watt and more. Small batteries have 10 thousand mAh capacity, etc…. In short, even Chinese manufacturers cannot overcome the laws of physics and do magic. I will also write my own article on this topic on occasion, because I have been ordering in China for almost 20 years and without any problems.
To make your purchase safer I will always give an alternative source with buyer protection, like Amazon.

So much for the installation of the electrical supply in my CamperVan. Details will follow in the implementation phase. How does the planning continue? The water supply is at least as important as the power supply…