Solar system on motorhome what should I watch out for?

I thought about making a solar system on the roof of a WoMo over the summer. Now it is the case that I have no plan of what to look for.

Suppose I would want to charge a cell phone there, for example, use the Playstation, fridge, TV, so much like in a normal stall, what should I look for in the devices? My electricity consumption is super low at 3000khw per year.

If I look online for a solar system there's something of 100W or 200W how do I find out how many devices I can use?

Please gladly declared for idiots!

So if I understand that correctly, you will start from scratch.

then I would advise you to install a 24, maybe even 48 volt system. Simple background: the higher the system voltage, the lower the losses in the cables. Accordingly, the batteries can be better used due to the lower current.

With the planned devices, you need an inverter like this. That makes a little something.

With a 24 volt system, you can charge various things such as your cell phone, lighting, etc. You can still feed directly from the battery. And also feed the "shore power" into the system via a charger. In a 48 volt system, I would then work with a transfer switch and do without the charger and operate everything at 230 volts.

your inverter should be a pure sine wave device with a power of at least 500 watts. I would, depending on what else comes, tend to tend to more.

as far as the performance of your panels is concerned: 200 W means e.g. That when 1000 watts per m² of sunlight shines on the KALTE panel (max. 20 ° C) 200 watts come out at the back. You only have that in the sahara when it is still cold in the morning. Around 850 watts per m² are realistic on bright summer days

Incidentally, I would not do everything about heating electrically, but with gas. Including coffee cooking etc. Because performance as well as battery capacity cost.

Incidentally, for your annual consumption of 3000 kWh, which is still present, your motorhome is guaranteed not to have enough roof space.

What should he do in a motorhome with 12 V on-board voltage with a 24 or even 48 V system?

You first have to be clear what kind of electricity you use in the motorhome on average per day.

To do this, multiply the consumption values of all devices by the average runtime.

Then you have to consider how long you want to stand self-sufficient. The battery is charged in a different way when driving.

Then the question is what time of year (and where) you want to use the motorhome.

The wattage for the solar modules is the nominal power or peak power in Wp under standard conditions. You can do little with that in practice.
In the summer half-year in Germany you can roughly assume that with a 100 W module, which is not shaded, you will have an average of about 30 A daily yield.
On rainy days, of course, there's also significantly less. In order to be able to recharge the batteries at the end of a rainy season, there may already be an excess of solar capacity.
Then you also have to consider that losses occur when storing and releasing energy in the battery. When operating 230 V devices using an inverter, losses of up to 10% are also incurred.

So: first determine the average daily consumption, then how long you want to stand self-sufficient.
Then you can worry about the rest.
Your information about your energy consumption at home is of no use here.

Very easily. The 12 volt should remain 12 volt. But the living area in the back can do more… As I said, where 16 volt cables are required for 12 volt, 4 mm² are sufficient for 24 volt and 1 mm² for 48 volt!

How much experience do you have with RV conversions and RV electronics?

24 V in construction is actually only made in vehicles with 24 V on the base vehicle, such as. B. For truck base vehicles. And mostly in order to be able to charge the body batteries directly with the vehicle alternator.

48 V in the camper body is absolutely unusual, I have never seen it myself.

With 24 V under construction it can sometimes be more difficult because you don't get all camping equipment with 24 V. There's no camper technology in 48 V at all.

And you don't actually have enough cables for large currents in the motorhome to make it worthwhile to go to higher voltage.

Apart from that, your statements are incorrect. If you need 16 qmm at 12 V, then it is 8 qmm at 24 V.

What you sometimes do is work with higher solar voltages, which are then brought back to the on-board voltage using the MPP controller. The reason for this is not the cable cross-section.

Hello emib5, thank you for your detailed answer.
Can you maybe tell me how I calculate consumption?
So if I understand it correctly, do I need the wattage of all my devices?
You can certainly research that.
So let's say I take my laptop, which uses about 60 watts. Would I then have to multiply the consumption by the duration? So assuming I use my laptop about 8 hours a day, is that a total of 480 watts? How is that calculated then?

Nearly. If your laptop has a power consumption of 60 W and you need it for 8 hours, that's 480 Wh (watt hours - I wasn't quite correct with the solar yield, it should be 30 Ah).
If the laptop always draws 60 W in time. If the battery is full, then not.
In some cases, you also need to know whether the nominal power is consumed permanently or only temporarily, e.g. B. At full load.

In order to determine the required capacities, it makes sense to convert the whole thing into amperes or ampere-hours. Because that is also the unit in which the battery capacity is measured.

And you should know the current in A later anyway, in order to be able to reasonably dimension lines and fuses.

The power in W results from the current that flows at a certain voltage, or vice versa.
To determine the current divide the wattage by the voltage. (Ok, not 100% correct for alternating current, but sufficient for home use.)

Your 60 W from the laptop would be approx. 0.26 A at 230 V

You are interested in the motorhome, but rather the power consumption with on-board voltage. Let's take 12 V. (Even if the 12 V battery usually has a little more voltage). That makes 60 W / 12 V = 5 A. If you operate the laptop via an inverter, you can now include another 10% loss.

At 8 h operation with 60 W that would be 40 Ah. (Without losses)

To the 24 volt:

a connection between the electrical system in the living area and the vehicle electrical system is generally not necessary. The only exceptions:

Charging the board battery via the vehicle alternator (can be implemented if necessary using a step-up controller, but does not occur if necessary because PV on the roof does this better
self-help: this is also possible if you tap the positive pole on the center tap. It's only for emergencies

to the cross sections: a 5 m long device lead with 1 mm² already has a resistance of around 0.2 ohms on the way there and back. At 10 amps, this already results in 2.4 volts of voltage loss. That corresponds to about 20%

same constellation at 24 volts: we get by with 5 amps at 120 watts. We have only 1.2 volts lost. Which then just corresponds to 5%.

to the choice of accessories: for 24 volt there's a lot of stuff. Almost more than 12 you just have to know where. E.g. In the truck shelf

for the 48 volt system: it was intended here to operate EVERYTHING directly with 230 volts via the inverter. High power consumption is not a problem here.

Are you sure about the 8 mm²? I'm sure that it is NOT exactly so, because with double voltage with comparable performance the current consumption is halved, which in the end not only halves the relative voltage loss, but also quarters it.

Unfortunately you did not answer the initial question. But this is no longer necessary, because from your answer you can read that you have no idea about camper van bodies. Sorry, unfortunately.

In contrast to you, I have over 30 years of experience in the planning and construction of electrical systems in residential and expedition vehicles.

Charging the body battery while driving through the vehicle alternator is an absolute standard and in no way unnecessary because of a solar system. Because e.g. B. In bad weather or in winter, the solar system does nothing. If, like most motorhomes, you have an absorber refrigerator under construction that you operate when you are standing by gas, then (while driving with electrical operation) via solar, it usually does not work sufficiently because the power consumption is too high at 12 V.

Yes, there are a lot of 24 V articles on the truck shelf. But I'm not talking about general car accessories, but about special camper accessories or camper equipment such as. B. Heating, boiler, refrigerator, water pumps, chemical toilets with built-in rinse water pumps, roof hoods with motor drives, roof hoods with integrated fans for the wet room, stove with electric igniter, electric remote switch for the gas supply, electric ice-Ex for the gas system, etc. Etc.

Yes, there are a few things of that with 24 V. But not everything.

And interesting that you want to operate everything in a camper with a 48 V system via an inverter to 230 V. Apart from the fact that you then again have problems finding the appropriate and suitable devices for everything (e.g. Have you ever seen a vehicle heater with 230 V control electronics? - I haven't) you are still automatically trading in the converter losses. In the camper you should keep an eye on your energy consumption, because the capacity of the body battery is finite. The solar system does not help, because a large part of the electricity is unfortunately needed in the evening, at night and in the morning when the solar system is not yet delivering.

Because of the batteries, excessive current consumption can be a problem even at 230 V via inverters.

Certainly… But better no idea of motorhomes, of which I have only made 2 so far, but 7 self-sufficient summer houses and ALL were ultimately satisfied with my work…

and ONCE AGAIN who cares if I have 12, 24, 48, 72 or 230 volts in the living area when I have the right geese. Let the 12 volts of the cart stay 12 volts - nobody cares if the electricity comes from the pv anyway…

and again! The cross-section requirement quarters with the doubling of the voltage with the same power consumption. I have not learned the disc for 40 months for nothing!

Yes, I'm certain about the cable cross-sections.

Because the line cross-section goes directly into the formula for the voltage drop.
Voltage drop = specific cable resistance x cable length x current / cable cross-section

Your calculation examples above regarding the voltage drops are not correct and are only of a theoretical nature.

The voltage drop in your example is still 2.4 and 1.2 V, but 2 u. 1 V. And 1 qmm for 10 A is often used in series vehicles, but it makes no real sense in the motor home. I prefer to dimension the cable cross-sections sensibly and appropriately.
You have such high currents in the camper body anyway, either not or only little.

You were now too quick with your comment, I already wrote something about the cable cross-sections.

Fine, so you've already made two campers? Really planned the entire electrical system, or "only" installed solar modules?

A summer house is just not a mobile home. There are completely different requirements.
And do you also read what I write: You do not have the right devices for your (in the motorhome) exotic tensions.
And I explained above that you don't usually only get along with the PV in the motorhome.
You do not need to repeat this stubbornly without further factual arguments.

Believe me, I pretty much know what's going on in the motor home and what's not.
I have my own motorhome, which is normally self-sufficient with solar power from spring to autumn. But this is not a normal-sized mobile home solar system, the energy consumption is optimized and is constantly monitored, and I operate e.g. B. Also no television. And solar power is not enough in winter. Even with a rainy phase lasting several days, it will only be tight at some point with solar.

The complete electrical system. Number 1 was a converted van. Number 2 an old gutted camper where we did everything new in the living room.

in number 1, we did not make any low-voltage electrics (apart from the batteries, the pv and the inverter (on the input side), but simply everything directly to 230 volts. Including the refrigerator.

in the conversion 24 volts and completely dispensed with the 230 volts. What for?

Believe me, I pretty much know what's going on in the motor home and what's not.

Pretty much is not enough!

Obviously you don't understand so much about electrical quantities and their calculation:

Apart from that, your statements are incorrect. If you need 16 qmm at 12 V, then it is 8 qmm at 24 V.

These are the basics, if you don't have them you shouldn't work in the field.

I put a quote here that proves Peppie's thesis:

The losses in the transmission of electrical energy are proportional to the resistance of the line and the square of the current. It is therefore desirable to keep the current as small as possible. Since the transmitted power is itself proportional to the product of current and voltage, the same power can be transmitted at twice the voltage with half the current and consequently with only a quarter of the losses.

Source: https://silo.tips/download/physikalisches-schulversuchspraktikum-3#

Btw. The proposed 24V solution is an efficient and effective solution under the given circumstances. It is not for nothing that the voltages in the vehicle area are getting higher.

Combining the question of quantity with quality is completely absurd.

Rather 2 times right than 30 years wrong.

I would like to thank Peppie in your place for patiently explaining how to do it right here!

Do not park in the shade.

The following articles give you a basic idea of what to look for, what options are available, configuration information and how, if necessary. Is installed.

Not all perfect, but really helpful for getting started:

https://www.solaranlagen-portal.de/photovoltaik-technik/passende-solaranlage-wohnmobil-wohnwagen.html

https://www.solaranlagen-abc.de/solaranlage-fuer-wohnwagen/

https://de.camperstyle.net/solaranlage-auf-dem-wohnmobil/

Here are a few alternative examples with flexible modules (easy and more flexible to "process", but somewhat more expensive and somewhat less efficient):

https://greenakku.de/mobilPV:::124.html