Electrical system architecture

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TheMobileWanderer

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I'm drawing up plans for my new self-build MH.

Would anyone be kind enough to see if I have overlooked anything?
(Bracketed comment removed to avoid people being easily side-tracked).

My aim to to have scaleable systems so batteries and solar can be swapped out, as panel power evolves.
Peak usage means IF I were to run everything off Battery, even though in all likelihood I wouldn't.
So peak usage could be 84Ah for about 2 hrs (cooking a meal). (2kW / 240)
Rest of time/continual normal usage (including periodic kettle demand), 21Ah ( 5kW / 240).

Solar power (input side)
Solar panels (2000W)
Cabling to charge controller
Isolator switch
Charge controller
Cabling to Battery pack
Inline fuse (what size?)
Battery pack

ICE power(input side)
Thick cable to B2B charger (up to 4m long)
B2B charger
Inline fuse (what size)(how to calculate)
Battery pack

Shore power (input side)
Connection fitting
Charge Controller 240V to 48V
Inline fuse (what size. How to calculate)
Battery pack

Storage
Lithium (Sterling 48V) 100Ah

Output side
Power inverter 48V to 12V 5000W
Power inverter 48V to 240V 5000W
Consumer unit (fuse & trips box)


I'm guessing the 5kw inverter is too small for peak times
I'm guessing Battery size isn't enough for much time off-grid.

Open to your suggestions too please.
TMW
 
Last edited:
TheMobileWanderer said:
I wish manufacturers would show batteries measured in terms of how many 2kw kettles they'll boil from full charge.
Click to expand...
No that simple, I'm afraid. How many pints is your 2kW kettle? How many people will be drinkng the tea?

Quoting battery capacity in Ah makes a lot of sense.

As described in another thread, you can work how much the kettle needs.
In that case, the answer was 8 Ah to boil that specific kettle.

Easy enough to work out how many times you can do that with your particular battery.
 
Last edited:
LithiumConvert said:
No that simple, I'm afraid. How many pints is your 2kW kettle? How many people will be drinkng the tea?

Quoting battery capacity in Ah makes a lot of sense.

As described in another thread, you can work how much the kettle needs.
In that case, the answer was 8 Ah to boil that particular kettle.

Easy enough to work out how many times you can do that with your particular battery.
Click to expand...
Battery capacity in Ah can be very confusing. Case in point .... you quoted a thread where boiling a kettle used 8Ah?
The OP here is talking about a 48V battery - in which case that very same kettle would take 2Ah out of his battery.
See the confusion?

Amp Hours and Amps are all dependant on voltage. The best common measure is WattHours and Watts as they are voltage agnostic.
 
Not sure about your peak usage calculations, think they may be low. Your battery is only 4800 Watthours together. It must be a very big vehicle if you can get 2000w of solar on the roof, perhaps 10x 200w panels.
 
I would suggest 2 inverters for your 240v needs, one dedicated to cooking (probably the only large load) and the other for everything else. Separate circuits tho unless you find a brand that will parallel. Larger inverters tend to get expensive too.

With lots of solar and 48v consider a domestic type controller perhaps, instead of many individual boxes, a much simpler install perhaps. The off grid type suit best, still allowing 240v input, hook up or generator, battery charging and inverter all in one operating in a few modes to suit your use. There's lots to choose from and you sound like you are making a house on wheels ;)

You'd still need B2B but with 2kW of solar you wouldn't be so reliant as those with a 200W panel.

Decide for yourself how much power you will use, but you're never going to feel you need less battery, get plenty. 48v batteries are great for keeping the cable size and losses down, consider 2 x 24v batteries for ease of fitment and more choice of battery.

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Hoovie said:
The OP here is talking about a 48V battery
Click to expand...
The vast majority of us use 12 volts in our motorhomes.

The people who use 48 volts know what they are doing and only confuse things by talking about it in a motorhome forum.

In this thread, I have to admit to missing the references to 48v - Mea Culpa.

But having read it all again, it is clear that the OP comes from a marine environment - reference to Shore Power, etc.

Once again, the thread only causes confusion on a motorhome forum.
 
Reallyretired said:
Not sure about your peak usage calculations, think they may be low. Your battery is only 4800 Watthours together. It must be a very big vehicle if you can get 2000w of solar on the roof, perhaps 10x 200w panels.
Click to expand...
Domestic panels typically are 450W and 1.7m by 1.1m. You could fit 3, maybe 4 of those on a ducato van roof is you needed to. Smaller panels would be easier width ways. Roof vents and weird roof contours can reduce the flat are on coach built.

Many ways to fit solar on a camper or MH, but most motorhomes despite their size don't seem built to take much solar.
 
Thank you for your replies. Some good food for thought.
LithiumConvert
I shan't bite, however, suffice to say, I wasn't aware of a rule that only 12v can be used on an MH. Wasn't aware either that I should go to a marine forum to find out how to power my MH. Principles are the same. Both are mobile and utilize 240v, alternator 12V and solar 12V. Only the storage is (potentially), to be 48V. All terms you seem annoyed about; I picked them up in these forums.

Hoovie: Thanks, we might think similarly lol
Reallyretired: Thanks, yes, I have seen 500W panels. I thought they were for MH but, I 'll check again and, if they're domestic, I shall check if they can be used on my MH. Whatever I use, they will be secured to roof rails/roof-rack to minimise drilling the roof and potential for leaks. Also for better deployability :)
I'd like eventually for 4 to be deployed by default but, when stationary, to have the ability to deploy 4 more up there, remotely, from the ground. That would be 8 panels at 500W.

Sewdhull: That's interesting - I shall look into 'domestic type controllers'. I'd like to be off-grid so I can go places where there's no sites/power hookups.
When at home, not using the MH, I'd quite like to explore plugging the MH into the home system, using it's power in the house.
 
OK, to maintain clarity, I've updated the spec list (battery) to take account of members' suggestions.

Still reading up on 48v power.

Curent spec list:
Solar power (input side)
Solar panels (2000W)
Cabling to charge controller
Isolator switch
Charge controller
Cabling to Battery pack
Inline fuse (what size?)
Battery pack

ICE power(input side)
Thick cable to B2B charger (up to 4m long)
B2B charger
Inline fuse (what size)(how to calculate)
Battery pack

Shore power (input side)
Connection fitting
Charge Controller 240V to 48V
Inline fuse (what size. How to calculate)
Battery pack

Storage
Lithium 2 x 24V 100Ah (Eco-worthy)

​

Output side
Power converter 48V to 12V 5000W
Power converter 48V to 240V 5000W
Consumer unit (fuse & trips box)

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Most of the people here are just enjoying their motorhomes and helping when they can or looking for help when they need it. Ah is what gets written on batteries and nearly everything is 12v because that's how manufacturers make em.

For solar panels you should look at your available roof space to see what you can in fact fit. I looked at the ducato and 1.7m wide was about all that could be fitted without overhang, and the ducato is quite wide. There's not really an RV panel etc, no reason not use a domestic panel which has a frame attached and a toughened glass front. Lots of physical sizes based on the wattage. Choose a panel whose voltage matches the solar charger, parallel if you can, in case of failure, but series is normal.

It's best to think about W Wh and kWh. Voltages matter of course to connect things up.

It's worth looking at lower wattage stuff, which takes longer to boil water for example but it means you can have all the normal things.

A normal domestic fridge is better in nearly all the ways than the MH offerings, a Combination oven is reasonable, induction hobs are great and come in various wattages. lower wattage kettles are a good choice.

The total wattage above is about 6kW. If you never use an oven its obvs a bit less.
 
My understanding is also that DC voltages needs to kept below 50v. Series PV voltages can be much higher than that.
You'll want to match the pv panels to the solar charge controller.
 
TheMobileWanderer said:
Thank you for your replies. Some good food for thought.
LithiumConvert
I shan't bite, however, suffice to say, I wasn't aware of a rule that only 12v can be used on an MH. Wasn't aware either that I should go to a marine forum to find out how to power my MH. Principles are the same. Both are mobile and utilize 240v, alternator 12V and solar 12V. Only the storage is (potentially), to be 48V. All terms you seem annoyed about; I picked them up in these forums.

Hoovie: Thanks, we might think similarly lol
Reallyretired: Thanks, yes, I have seen 500W panels. I thought they were for MH but, I 'll check again and, if they're domestic, I shall check if they can be used on my MH. Whatever I use, they will be secured to roof rails/roof-rack to minimise drilling the roof and potential for leaks. Also for better deployability :)
I'd like eventually for 4 to be deployed by default but, when stationary, to have the ability to deploy 4 more up there, remotely, from the ground. That would be 8 panels at 500W.

Sewdhull: That's interesting - I shall look into 'domestic type controllers'. I'd like to be off-grid so I can go places where there's no sites/power hookups.
When at home, not using the MH, I'd quite like to explore plugging the MH into the home system, using it's power in the house.
Click to expand...

Something I would give further consideration to is going for a 48V setup though.
12V is obviously the most common. 24V is also not that unusual and as people are getting bigger batteries and using inverters more and more, 24V is certainly making inroads. 36V is occasionally seen but is an oddity so best ignored. And with 48V, it is certainly doable but your choice of products are significantly less than 24V.

There is also maybe worth consideration of "what ifs" in the event of problems..
The question of solar panels was raised? with a 48V system (which will have a charge voltage of around 56V), you will need multiple panels needed to achieve a minimum voltage needed for charge. If a panel is damaged or fails, your array could be massively compromised. The impact for a 24V system would be lessened and give you some redundancy so still have a working albeit reduced capacity setup.
Similarly with batteries ... you want more batteries capacity than the 48V 100Ah one? you'll likely need to double up. If you had say a pair of 24V 100Ah batteries in series, you could be more modular and just add one more 24V 100Ah or even maybe 3 more to give you 500Ah @24V. And if one battery failed, you would just lose partial battery capacity and not the lot.

I had considered a 24V setup when I updated my own motorhome but decided on staying 12V just for the simplicity and also meant I could play around with the setup and try stuff (started with 3 batteries, and have at various times have had 3, 4, 5, 4 again, 5 again, and now currently 6 batteries installed (for 620Ah@12V). Staying 12V made that possible :)

Price of batteries now, and the fact for my DC Habitation Power I am actually using a 12V-12V DC Converter to regulate its voltage, I would probably go for a 24V installation if I were starting again.
Overall I probably use as much AC Power as I do DC Power (I have a 240V Fridge/Freezer) and when cooking I tend to use AC applicances (Induction Hob, Microwave, Air Fryer) but not so much that a 48V Inverters efficiency outweighs the negatives (IMO) that go with it. But of course, other people have different needs and there is no one size fits all.
 
Going 48v with only 5kwh storage is a mistake, costly one. You will need 10kwh battery for a 5kw inverter, and thats for short peaks, the continuous run ratio should not exceed 1/3. That will give you a 0.5C discharge peak, with 0.3C continuous.
If you can double the storage then stick to 48v and go for a 5kva multiplus. That will take care of shore incoming, and stick to ONE inverter, don't be fooled by ideas that actually nobody implemented them. Ppl preach but never lived with what they recommend.

Also do consider the 24v route, as it had advantages, major ones being almost any appliance, lighting at 12v is available in 24v as well, and you skip a DC converter.
In terms of panels, stick to large panels with good high voltage. I have two large 300w on the van.
Solar controller, victron 150/45 for a 48v system, or a 150/85 if you opt for a 24v system.
There is no such thing as domestic controllers, just size it up to your requirements.
 
My roof will be 2.5m wide and the flat part is 6m in length. Dimensions of each panel: 2279 x 1134 x 35 mm. Voltage: 540W each

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Last edited:
TheMobileWanderer said:
My roof will be 2.5m wide and the flat part is 6m in length. Dimensions of each panel: 2279 x 1134 x 35 mm. Voltage: 540W each
Click to expand...
Just under 2.4m by 1.13m you can get 600w plus panels. You got the space, also look at Canadian Solar option as well.
If you can get 4 large panels on the roof, to make a high enough string voltage, then you are in territory for Hybrid storage inverters as well, like SunSynk inverters. The advantage: no double conversion on direct solar usage, can do the shore charge, managed battery with CAN bus comms via inverter, dual mppt trakers, you may be tempted for a portable solar that could be used on the second mppt, and it can be paralleled with virtually anything.
 
Raul: So many phrases in that post, that are new to me, I'll take time out tomorrow to research their significance. Might have some questions.
 
TheMobileWanderer said:
Raul: So many phrases in that post, that are new to me, I'll take time out tomorrow to research their significance. Might have some questions.
Click to expand...
Not a problem, I will be happy to help, I do have few years of experience with off grid systems, started in 2012 as a roof top installer then 2014 my house was born, all of grid since. The van is a baby system. I've been trough all the changes and upgrades, few winters, adapting to new tech, etc. but the journey continues and still learning. 👍
 
Not sure how or why I haven't seen this. Voltanic 1200W panels (monocrystalline) with the dimensions,
1722L x 1134W x 30H mm (each).
 
It's a con or typo. Can't get that power out of that area.

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TheMobileWanderer said:
Not sure how or why I haven't seen this. Voltanic 1200W panels (monocrystalline) with the dimensions,
1722L x 1134W x 30H mm (each).
Click to expand...
I'd guess it's this kit:

Max-Power 1200W 24V Solar Panel Kit

The 1200W Voltanic Solar Kit is the perfect choice for bus conversions, static caravans, on and any building that demands larger than normal power requirements.
voltanic.solar voltanic.solar
So 3x 400W panels with those dimensions each.
 

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