Solar panels ,how large

nigelmercier said:
Typical Maplins. How fecking stupid is that!
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It's really for keeping car or caravan battery topped up. You lay it on the dashboard.......... it'd soon get nicked if you suckered it on the outside.


Many people find they dont work......if the car is in the garage either
 
nigelmercier said:
I see, I didn't look at the item, Maplins just makes me cross. I guess this also plugs into the cigar socket, where it will do no good at all.
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It will plug into the cigar lighter socket but it is also supplied with croc clips ....... Clever people these Maplins .. they think of everything.

At least one of our cars has the cigar lighter socket "live" when the ign is off, possibly two of them.
 
30boat said:
That's good but I was trying to do it on the cheap.I guess I'll have to bite the bullet eventually.The price is not bad actually.
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I had 2x40W rigid panels delivered from Germany to Spain for about £104 incl. VAT & Del. (ex. eBay) That's 80W vs. 20W.

So if you don't actually need flexible panels then stick with a cheaper rigid panel. Less financial risk and many people say that they tend to last longer than flexibles anyway. You will usually get better performance from a rigid panel but better shade tolerance from the flexible ones. Mounting issues might force you down the route to a flexible panel. However, that shouldn't be an issue for a winter top up panel if that's all you want.

I have 3 panels (65W + 2 x 40W) lying flat on coach roof. Performance since April this year has peaked at 82Ah (freak day) for a 2 hour period but normally around 65-75Ah/day. Worse lately due to lack of sun and very worst day was 34Ah.

Currently getting 110Ah/day from Rutland 914 (instead of usual 7Ah) and only 55Ah/day from the solar panels. Not so much sun but 34kn gusts yesterday and in early hours today. Can't have everything but at least the batteries are at 100%.
 
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I notice that no-one has mentioned the potential problem of over-charging batteries if solar is connected and no load is being drawn? If the objective is simply to maintain a battery that is already charged against self-discharge then a 5-10W panel should be incapable of causing a problem and should do the job. We have a small panel that maintains a caravan battery for us.

If however you are talking about solar to offset or balance the load imposed by anything: be it lights, entertainment, pumps, fridges, etc. then a much larger solar array is the way to go. That will be capable of overcharging the batteries if there is no load present, and it is essential to fit a regulator. MPPT controllers are now considerably more efficient and not so expensive. (See www.onlineladen.net).

As someone has already posted, it is a good idea to get a thorough understanding of your power requirements by monitoring and measuring your loads (amperes) over a period of time (hours). If you can mount sufficient solar to meet this you are in nervana.

Fridges are perhaps the heaviest culprits, entertainment and laptops might come second.
 
ghostlymoron said:
A recent discussion on here seemed to conclude that there was no real advantage of mppt £100 over pmw £10 controllers.
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The big problem with cheap versions of either type (mostly originally intended for street light applications) is that you cannot adjust the charging characteristics in any way. In boat applications they will reduce to charge to a low float voltage (13.8v) based on time, long before the battery has fully recharged from a previous heavy discharge. I override my (cheap) controller until I consider my batteries adequately recharged .... it then does a fine job of simply maintaining a constant float voltage as long as any load is less than the output capability of the panels.

(A big plus of the cheap street light controllers is that the 'load' output is ideal for dusk-dawn control of the anchor light!).
 
syfuga said:
I notice that no-one has mentioned the potential problem of over-charging batteries if solar is connected and no load is being drawn?.............

it is essential to fit a regulator. MPPT controllers are now considerably more efficient and not so expensive. (See www.onlineladen.net).
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I sail the same area as the OP. 200W of solar + Aerogen is sufficient for our needs including fridge (BD50F) running 24/7.

There isn't a problem with solar being connected when batteries are full and no load being taken, the regulator takes care of that so no overcharge.

As far as MPPT v standard regs, we have one of each, one to each domestic bank. Both banks are monitored with BM1s which show the cheapo reg gives a better charge rate than the more expensive MPPT.
 
nigelmercier said:
Got a link?

I don't think being flexible makes a difference to the shade performance, just the structure of the crystals (poly or mono).
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I know that the rigid panels are hugely affect by shade. I've seen claims that some "marine" flexible panels are wired to improve performance wrt shading. No 1st hand experience of that but I was giving them benefit of the doubt. I decided that rigid panels were easily best bang per buck and less financial risk as well. I have 3 panels and I'd bet shading effect is actually less than 1-2 flexibles.

I bought from solarventa on eBay. I haven't checked his prices but can do that later (downloading F1 race from BBC just now). Try a search for supplier solarventa.

Just found his shop: http://stores.ebay.co.uk/solarventa?_trksid=p2047675.l2563

TIP: I went in via ebay.es to actually place the order. I seem to remember that his prices were better there than via ebay.co.uk (think he adds a bit on for UK buyers, surprise.). It was def. cheaper that way when I bought the panels in April.

UPDATE: Just had a look at ebay.es and prices seem to be the same as the uk store now. I guess that he spotted the price difference some time after I'd ordered my panels.
 
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The OP was asking about simply keeping up with self discharge, with a view to simplifying installation, but a panel needs to be fitted properly if you want it to be there when you come back. To my mind there's just too much risk of having to buy your own panel back at the boat jumble if it isn't properly nailed down and, if you're going to go to that trouble, you may as well do it for enough to meet your needs.

I fitted two of Solarstore's 20w rigid panels (http://www.sunstore.co.uk/12v-Solar-Panels-c-286/) to Jissel and they, combined with a dual charger ensure that both batteries are fully charged when I come down to the boat even in the miserable spring we've had in the UK. Since we've had a bit of sun, it kept up with several hours a day of FM radio, electric water pump and LED lighting without raising a sweat. which sounds like something like the OP's needs.

I got two 20w rather than one 40w because of the shading effect. The only practicable place for them is on the hatch garage, under the boom, which means that the boom will often shade one panel or the other, but rarely both. Discussion with a supplier suggested that 20w full + 20w shaded would be more than 40w with the same amount of shade.
 
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