Power Independence! What size Solar Panel?

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Infr137

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Hi

I'm presently upgrading my boats electrical system and looking to compliment my charging system with a flexible solar panel. My ultimate aim to be independent of any shore power and minimal use of the engine for charging.

I've got a single 135AH Leisure battery and an 80AH Engine battery.

Aside from charging the batteries via the engine alternator, I also have a Rutland 503 wind generator. My max daily amp draw is approx 24 amps.

What wattage solar panel would you recommend given the above setup?

Many thanks in advance

Rob...
 
I assume you mean a daily draw of 24 Ah (not a continuous draw of 24 amps!)

To satisfy that you'll need a panel of about 60 watts. Maybe more if you want to be totally independent of charging from the engine, but why not fit the largest you have space for (two small panels can alwys be connected in parallel)

Id leave the engine battery to the engine (but with provision to use the house battery if necessary for starting) and concentrate the solar and windmill on the house battery combined via a suitable regulator. You could of course use a regulator with twin outputs to charge both batteries if you wish. The HRDX regulator will combine the output of the 503 with up to 100watts of solar panels and charge two battery banks.
 
I agree, fit as large a panel (s) as you can. Better to have too much than not enough. Assuming you have a charging management unit in place to stop overcharging.
 
Might gain benefit from fitting battery charge management from someone like Adverc or Sterling. That way you'll ensure when the engine is running the batteries get best charge.

Adverc
 
You don't say where you are and where you are going! We're on our way to the med and have fitted two flexible 68w panels on the foredeck in front of the mast. The great thing is they can be walked on, even in high heels, and blend well into the dark hatch covers. We managed to find some through-deck fittings that allow the wires to enter horizontally which makes the installation very safe and neat.

We do have a much higher daily Ah than you - but I would agree with others fit the largest you have room for.
 
The way I have been told to work out the size of solar panel required is as follows: -
(Panel Wattage / Panel nominal voltage) x 4 hours = Av daily output.
Remember the panel nominal voltage is as per the panel blurb not 12v. Alter the number of hours depending on where you are. I have been advised 4 hours for UK and northern Europe and 5 hours for the Med and Tropics and remember that partial shading can cut the result by up to 80%.
I have Kyocera 130W panels with a nominal voltage of 17v so the average output of one panel in the UK would be; -
(130/17) x 4 = 30.5Ah

I hope that helps.
 
That article was most useful Alan thank you and the advice from you all is much appreciated.

The boat will be in UK waters on the south coast and I did mean a draw of 24AH.

This tho would be my max current draw which would probably apply to 4 days out of a 7 day week.

Would it be worthwhile me calculating my non passage making draw then coming up with an average?

The wattage of the panel seems a tad excessive for a single 135ah battery. But then I'm no expert.
 
As you have a small Rutland 503, you clearly understand the advantages of wind over solar, eg 24 hour input etc. I have 400 amp hours of batteries, and a single 913 with HRDX controller which has kept the boat independant of shore power for 3 years.
I did have 2 x 15 watt solar panels as well but they proved not to be neccessary
 
I would ask why you are not satisfied with the wind gen doing the job.
Based in UK and with winter approaching I wouldn't bother with solar.

However the beauty of solar is that if you buy a small panel then decide it is too small then adding panels doesn't cost much more than the relationship of added watts and sometimes smaller panels are easier to find a place for.
Selecting solar panel size depends on the space available and budget. Small panels with large batteries won't need a regulator and they can be split to 2 batteries by fitting splitting diodes. Individual diodes for small currents are very cheap and providing you don't use a regulator the volt drop doesn't matter. olewill
 
I did a delivery a couple of weeks ago of a Dufor 44 that is on the ARC this year. The owner had installed what he felt was the ultimate charging system... a fuel cell.

It is the first one I have seen on a boat but I have to say that I was impressed. It runs on Methanol, weights just 7kgs and almost silent. It monitors the electrical system and turns itself on automatically when the batteries charge drops so it is a set and forget. All you have to do is top it up occasionally with methanol.

http://www.emarineinc.com/products/fuel_cell/fuelcell.html

They delivery 100A per day if running flat out but as they only run when needed so just deliver what you need.

I liked it but it is expensive but it does get rid of solar panels and wind gennerators and no more daily engine running.

If you have the cash... IMO this is the way to go.
 
[ QUOTE ]
But where does one get methanol in this country

[/ QUOTE ] eBay.
Sold for biodiesel production. Is 99.95% pure. A Google search will turn up other sources.

Stumbled on one supplier in Glasgow!

It is as well to remember that it is highly flammable so some consideration must be given to safe storage
 
The Rutland 503 is little more than a trickle charger, it is the first step up from a forgen type.

<span style="color:blue"> Produces 25w in 19 Knots </span>

It has its place, don't get me wrong, but he will need to go up a size to get the independence he cherishes. My suggestion would be a bigger windgen before buying panels, but he does not say what type of boat he has so that may not be possible.
 
The fuel cell, seems like an excellent idea, though alas prohibitively expensive for me.

My boat is a 23 footer, so something larger than a 503 tends to be almost 3 times the weight as well as looking a tad ridiculous for the size of boat. Hence thinking about solar.

I did see mention sometime ago of a dedicated charger that goes in the water, therefore charging when under way or in a strong current. Can't remember what it was called.

Current thought is to get a full featured battery monitor, and make regular notes on "Actual" ah usage rather than max projected usage. Good idea?

Appreciate everyones thoughts/comments to date.

Rob
 
Aqua gen or duo gen is what you are referring to wrt towing a generator. If I was replacing my aerogen4 now I would seriously look toward the duogen, but both the towed gens are substantial bits of kit.

At 23ft, you're right that the bigger windygens start to become to large and solar is your option.

Adding to panels, I think you are going to need to increase your battery capacity, go for storage through the week rather than trying to keep up with your usage, if you see what I mean.

I have just added two 50W panels, on one of the few proper sunny days since, I have found it peaked at about 2A per panel, they are rated at 3.1. These are pretty large panels, well actually they are small compared to many, but trying to attach them to a 23ft boat might be a struggle. I have a cat so have a rather large coach roof and luckily they disappear for me on a 26ft'er, but I am not sure you will find the same.

There is also the KISS system, have two batteries and take one home to charge, swapping them on arrival? not great though.
 
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