Solar Power and Caravan Voltages

mjt57 · Senior Member

Solar Power and Caravan Voltages

Muzzlehatch · Senior Member

My set up is a "roll your own" designed for long term off grid free camping. I have 2 x 200Ah batteries and 650W of panels. If you have much more than that on a van it gets big and unmanageable. From this I run a 12 v Engels / LED lighting and sundry DC > DC converters for monitors and laptops. I also run a 800W 240 inverter for the rare occasion I run a bread maker (mix and rise cycle only) / rice cooker / blender / 50 inch TV / cordless power tools. The 240 volt is run on plug boards so I dont have installed power and I dont have a 240V IN for a powered site.

All the other cooking gets done with gas.

Once you start to run the numbers you will see you have to be very frugal with the PV power available unless you want to er cranking up a gen-set regularly.

HTH ..

Baz421 · Guru

Martin

We have systems very similar to houses in vans in that the PV output is regulated and charges the batteries AND used directly during the day when PV is supplying current. The fact that the PV output goes to batteries rather than the grid is the same principle,,, ie excess power that is not used immediately is stored/sent to the power grid.

The batteries are then connected to an inverter that can deliver the power at night for instance rather than drawing power from the grid. The inverter can be switched on/off at will.

So the PV system can be directly wired to 240V inverter but why when 240V use in a van is usually intermittent, and predominantly during the afternoon/night IMHO.

Remember if you do it like a house you cannot draw power form the grid at night unless in CP with 240v available, and if you do this the power that you could have stored in your batteries during the day for later use would be wasted.

I hope this makes sense.

Cheers Baz

PeterD · Guru

Martin, 240 V power appliances are very power hungry. You can run a house on solar, it is done frequently but takes a lot of batteries to do so. As an example go to http://caravanandmotorhomebooks.com/all-solar-house/ and see an example (scroll down to the heading "The solar system.") You may not need such an extensive system in a van but the size system required would still be heavier than the load allowance of your van.

To overcome this we use a few low power appliances that operate on 12 V. Even then some run out of power after a few overcast days, particularly in low latitudes like Victoria and Tasmania. To go camping off power you must forgo many of the so-called comforts of home.

You have probably been seduced by the purveyors of inverters at caravan and outdoors shows. They spread the word that simply purchasing one of their large inverters you can run anything from a battery that you can run at home. They just dont mention how big the battery has to be. They are the kin of snake oil salesmen.

mjt57 · Senior Member

PeterD wrote:

You have probably been seduced by the purveyors of inverters at caravan and outdoors shows. They spread the word that simply purchasing one of their large inverters you can run anything from a battery that you can run at home. They just dont mention how big the battery has to be. They are the kin of snake oil salesmen.
Thanks folks.

Peter, we've only visited two caravan yards. And have had little interaction with their sales people. It's just that I noted that vans have two separate electrical systems. Hence the questions.

Cheers

Martin

Muzzlehatch · Senior Member

Martin,

you are very welcome. Even to those of us with a background in electronics, PV / battery systems can be infuriatingly quirky despite the apparent simplicity of the set-up. It will reward your attention to do plenty of research and feel free to ask questions.

I have yet to find a definitive resource.

As Peter says there is a lot of misinformation. I just clicked off a you tube clip of some half baked off grid prepper zealot enthusing about PV. For all her enthusiasm she ad absolutely no idea what she was talking about. You get a lot of that.

cheers !

PeterD · Guru

mjt57 wrote:
Peter, we've only visited two caravan yards. And have had little interaction with their sales people. It's just that I noted that vans have two separate electrical systems. Hence the questions.
Martin

Martin, you are a rare character. You have done your research early. Generally the new members her come to the forum to solve problems resulting from unwise decisions made before they have done their research properly. Keep asking questions here and you will be able to walk away from those salesmen who feed you duff gen when you come by them.

Jaahn · Guru

Hi Martin and Muzzlehatch, smile

If you want to get a definitive book resource on this subject then I would recommend this one or another from his very informative range of books. http://caravanandmotorhomebooks.com/product/caravan-motorhome-electrics/

Colyn Rivers has written quite a few books on Solar and fitting out Caravan electrics and Solar for Caravans etc and also Solar for self sustaining houses. He has been doing all that and using it for years. Australian too. The books are available in lots of places as well as direct. Your local library may have a copy for a preview even.

Jaahn wink

The full list of Books by Collyn Rivers

Jaahn · Guru

mjt57 wrote:
Hi. We're new to the world of caravanning. So new in fact that we don't own one yet! Anyway. I'm reading up on the accessories for vans including solar power. They all seem to run separate systems. Ie. 12v and 240v. How come they don't have systems configured like your house that is. The solar PV and inverter connected to the 240v electrics? Thanks Martin

Hi Martin smile

I have posted a book reference on these subjects and perhaps the cost is so insignificant compared to the outlay on a new van or motorhome that I am surprised Colyn does not sell out. However ---------

To directly give an answer to your question. At home we are connected to an almost unlimited source of 240V power. We are familiar with it and just flick the switch. Want more heating just get a bigger heater and plug it in etc. Our great electrical standards ensure that the potential danger of the 240v wiring and its use is minimised and we know that we have to be careful with it. hmm The home solar systems are linked into that to supplement the supplied power and inside you do not know where the power comes from, just that it does come at the flick of a switch and it is all safe to use. Great stuff really.

However out in the great outdoors in your van, life is more constrained. The fact that it is not connected to the power grid permanently means the system is not foolproof either safety wise or power availability. Even when you plug in at a caravan park these factors are not always 100%. The park power point system is limited to 3600watts max supply and the safety may not be as good as at home either. Your van only has an earth when it is plugged in.

Putting solar and batteries in for power is an alternative, and the fact that it is a lower voltage system at 12v or 24 volts makes it safe in practice and also by the regulations. It can work well but the power is limited and you will have to 'keep an eye on it' so you do not use more than you make! Obvious really wink

However if you then convert this safe low voltage power into 240 volts AC power there are other factors which come into the picture. Safety is one. Overuse of power is another. Even use of 240v generator power has its problems of how to use it correctly and safely. There has been lots of discussion on this forum on the subject. hmm

Jaahn

Opps, just had a seniors moment ! Thanks Frank bleh

-- Edited by Jaahn on Thursday 10th of September 2015 12:18:12 PM

-- Edited by Jaahn on Thursday 10th of September 2015 12:32:20 PM

KFT · Guru

At the standard Australian voltage of 230 volts AC a 15 amp power outlet will normally supply 3450 watts. If the voltage is higher say 240 volts then the outlet can supply up to 3600 watts.

frank

mjt57 · Senior Member

Thanks for your input, folks. It's appreciated.

A bit of background. I work in the power industry (generation) as a technician. Whilst not a sparky, I do have a reasonable knowledge of the stuff as it pertains to my work. I am, however, unfamiliar with the background of caravan electrics, but am learning. ie. why there are two separate systems and what they do.

I've also started to browse the forums, the Grey Nomads website and others. One thing that seems to stick out is the use of generators. Apparently one can be "pariahised" if you rock up to a camp site, set up the 'van and hook up the Honda generator. So, socially, I suppose that I'll need to be on top of the solar thing, what my requirements need to be and what its capabilities are, and ergo, limitations on what I can do.

However, to start off, we'll be getting used to living out of a 'van and the main thing, towing it and towing it long distances. Already the missus wants to go to Alice Springs!

Anyway, I'll keep reading and if necessary keep pestering people with questions.

Thanks again.

Muzzlehatch · Senior Member

mjt57 wrote:
Thanks for your input, folks. It's appreciated.

<snip>

However, to start off, we'll be getting used to living out of a 'van and the main thing, towing it and towing it long distances.
<snip>

Anyway, I'll keep reading and if necessary keep pestering people with questions.

Thanks again.

As a general philosophy I reckon you are bang on with that approach. I have been living in my caravan and fitting it out at the same time. It is so easy to get a great idea and get all enthusiastic. You incorporate the idea into the build only to find out 1. It just isn't going to work ever. 2. It will work but with modifications. Now I prototype something and build it roughly. Live with it for a few weeks to see if there are any tweaks that need doing. Then finish it off. That way you dont commit yourself to barking up the wrong tree. What will work just fine for one person (I like it pretty spartan) will not suit other folks.

My big mistake was to rush ahead and build a 24v system that was too generous, however the downsides out weighed the advantages so I downsised. Time consuming and expensive.

The "cut and try" philosophy works for me.

mjt57 · Senior Member

Muz, chances are that we'll be buying a used caravan. Friends had one built recently. A single axle van with all mod cons. Mob in or around Carrum Downs, a south eastern bayside suburb in Melbourne built it for them. We also looked at a mob in Kilsyth recently, up the road from World of Caravans (eastern suburbs). They are branching out into vans now that they're about to lose contracts to supply car makers with body parts. But they do build the pods for police divvy vans here in Victoria. Their cans, one called the "Karacampa" look OK, too.

But our budget doesn't extend to $50k+. So, used it will be, I think.

So, hopefully, whatever we get will have the solar panels and the required equipment to go "off grid" if required. It's then up to us to modify the car to accomodate a dual battery system and keeping the van charged.

Phil C · Guru

Hi all,

We struggled with these questions as well. The conclusion was a compromise between weight and need.

We have 2 110AH batteries, a fixed 120W panel, a portable 120W panel and a 2000W Generator.

So far, touch wood, we have survived the bush camps with visits to a caravan park every 5th day.

The inverter question will always be a major pain for some. We have a feebay, 2500W pure sine wave inverter, it powers my coffee machine and the electric blanket as well as charges the non USB stuff. I dont expect the world from my inverter so Im not disappointed when it doesnt power my aircon. In summer we have small 12 volt fans and in winter the electric blanket keeps us comfortable.

I think this whole question revolves around how smart we are and what features and "comforts" we can do without. After all we are at camp. Mind you, in saying that we still live very comfortably off the grid. We have TV with DVD, LED lighting, gas cooking and refrigeration. Our 240 volt use is minimal as most of our stuff is 12 volts (battery).

BTW I have yet to use my generator at a free camp, it is there for that dull day to top up the battery.

Good luck with your choices, PeterD is 100% correct in saying do a lot of research and I will add be prepared to make some compromises. We did a big list of wants vs needs and came out looking pretty lean and mean.

Cheers

mjt57 · Senior Member

What I'm starting to realise is that weight is a major factor in what we want to put into a van, or indeed, into the car that is towing it.

We could go to town with solar panels heaps of batteries, generator and so on. But it all adds up. Might not have allowance for the pots and pans, otherwise...

Looking at the rated weights of vans there are two figures. ATM and Tare weight. There often isn't much difference between the two, particularly if say, 200kg of that is taken up with water along. Some vans that we looked at had an all up weight (ATM) of about 300kg above that of its unladen weight. Or tare weight, or kerb weight. Oh, wait. I'm confused now...

In any case, it leaves little room for extras, it seems.