Solar how to know how much I need?

[Darcar]

I'm looking at fitting solar panels to the roof of our van. The van is a Mercedes 814 so plenty of space!

I will be using a compressor fridge, & blown air heating which I think will draw the most! Then we'll have 20 led light scattered around? The power to the cooker ( lighting it ) the power to the toilet, and the water pump also a 12volt phone charger socket . Theses will all run form the LB which will have a split charger & mains charging when 240v is available.

Our VB is running 24v via 2x 12v batteries I intend to only use 12v in the habitation side and still have 2x 120Ah batteries.
I hope I've given enough info here? To work out the amps I'd need.
Secondly. What's the difference in the different solar panels available and controllers ?
Thanks Darren..

 

[wakk44]

A few variables there,what time of year will you be in the van,whereabouts in the world and for how long do you need electrical independence?

There's some useful information about solar power from the C@CC which answers some of your questions....Solar Power - The Camping and Caravanning Club

Of particular interest is the following chart which shows the big difference in solar output between summer and winter.

 

[iampatman]

It's a long read but probably worth it.

http://www.caravanfacts.com/modules.php?name=SolarCalc

Hope this helps,

Pat

 

[Fazerloz]

We look to have similar requirements to you and have 200w of solar. In the winter we can go about a week without a boost. The rest of the year no problems. We have 140 amp LB. In winter blown air heatering is on all night and also run a compressor fridge.

 

[trevskoda]

200 watts on roof will keep batterys charging during good daylight but they will not keep up to demand 24/7 as there will be a loss at night which may not be fully recovered during day,so a few days or so and a engine charge over a few hrs run should bring them up again to full charge.

 

[witzend]

Some info here worth a read A & N Caravan Services : Solar Power

 

[trevskoda]

Some info here worth a read A & N Caravan Services : Solar Power

Thats the way my van is wired up with fuses on both sides of solar panel,and as i always said bosh s5 or varta silver are much better than so called lez or traction batts,so im not as daft as my teachers told me.:banana:

 

[st3v3]

The simple answer is cover the roof.

You can never have too much, and too little sucks.

If money is an issue, buy what you can afford, but make sure the controller will support a roof full for later.

 

[Darcar]

A few variables there,what time of year will you be in the van,whereabouts in the world and for how long do you need electrical independence?

There's some useful information about solar power from the C@CC which answers some of your questions....Solar Power - The Camping and Caravanning Club

Of particular interest is the following chart which shows the big difference in solar output between summer and winter.

Thanks.. We intend to use the van in the spring winter and Autumn. Not keen on summer it's all to busy ! We probably won't be off grid for much more than 5 days at a time. Mostly in uk, Europe & North Africa.

 

[wakk44]

Thanks.. We intend to use the van in the spring winter and Autumn. Not keen on summer it's all to busy ! We probably won't be off grid for much more than 5 days at a time. Mostly in uk, Europe & North Africa.

I think the reply from Fazerloz is very helpful..................

We look to have similar requirements to you and have 200w of solar. In the winter we can go about a week without a boost. The rest of the year no problems. We have 140 amp LB. In winter blown air heatering is on all night and also run a compressor fridge.

He has a similar 12v usage to you and with 200 watts of solar can go a week without a recharge in winter with a smaller leisure battery capacity.It's all right doing all the calculations but you can't beat someone who has had practical experience.

I think if you go for a 200 watt solar panel system on the roof as Fazerloz has done you should be able to last at least a week in winter without a recharge and be electrically independent for the rest of the year.

 

[roamwood]

We have pretty much the same setup of twin (90ah) batteries, a compressor fridge and led lighting throughout but with a total of 420w's of solar panels (one 330w, one 90w). You would expect us to be self sufficient, but even if the van is just parked on our drive (with only the fridge running) 1 or 2 prolonged gloomy winter days can fully deplete our battery bank. Its easy to see why, our fridge consumes on average around 4Amps, and yours is likely to be the same. In the winter you would be lucky to have usable sun for 6 hours per day so each of those 6 hours need to be providing 16ah just for the fridge! A 200w panel would be doing extremely well to provide half of that in full winter sun so at best it would only extend the interval before hook up was required.

Don't forget that conditions for your panel are rarely optimal, particularly when your panel is lying flat and the sun is low in the sky over the winter. More capacity the better in my book, your solar controller can always throw away excess energy when you have too much. A genuine "MPPT" controller is great as it will allow you to recover more energy from your panel/s and will also enable you to use larger higher voltage panels such as those intended for houses which are often cheaper to buy. A PWM controller will typically throw away around a third of the power your panels produce simply because when your "12v" panels are producing full output, that output is at 18v. An MPPT controller can convert those excess volts above 14v into more amp hours. Our first 60w panel / PWM combination never produced more than 3amps even in the height of summer which is why we have gone for 420w now.

A decent 30a MPPT controller will start at around £130, look at anything cheaper than that with skepticism! Many MPPT controllers on eBay are not even good PWM units. If budget is tight and roofspace isn't, there is an argument that the extra money spent on a MPPT controller might be better invested on an extra panel. Then it is relatively simple to upgrade the controller later if you need more power.

I think my recommendation based on my experiences would be to aim ultimately for a minimum 400w system if you wildcamp much in the UK when the days are shorter, unless you very rarely stop in one place more than one day. If your motorhoming is mostly short stay, or summer time and sunny lattitudes, 200w might be enough.

 

[Deleted member 2572]

We look to have similar requirements to you and have 200w of solar. In the winter we can go about a week without a boost. The rest of the year no problems. We have 140 amp LB. In winter blown air heatering is on all night and also run a compressor fridge.

You will have to explain exactly how you manage that and your set up as no one I know can compete with that in the winter.
What is your secret

 

[trevskoda]

You will have to explain exactly how you manage that and your set up as no one I know can compete with that in the winter.
What is your secret

He parks outside a nuk power station.:lol-053::lol-053::lol-053::lol-053::scared:

 

[Obanboy666]

You will have to explain exactly how you manage that and your set up as no one I know can compete with that in the winter.
What is your secret

I cannot with 220 amps of battery and an 80 watt panel. In winter the solar is next to useless that's why I use a generator.
I am a tv addict through a sky box which is a heavy demand but don't have the heating on overnight.
Even without the tv I wouldn't last anywhere near a week.