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Old 21 February 2009, 16:57   #1
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Solar Panel

Hi everyone,

I have a solar panel fitted to my rib to charge the battery. on the box it says you cant have the solar panel attached to the battery when you start the engine. this is true because i had a solar panel on my boat and forgot to unplug it and started the i think it blew up but anyway it didnt work. I was just wondering... on my rib i have 2 150w marine speakers and a car cd/radio, if i was using the stereo and speakers with the solar panel attached to the battery would it do the same thing and blow it up?

thanks for your help,

alex
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Old 22 February 2009, 03:45   #2
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you could put a resistor in the cable coming from the panel, that would only let the current go one way and not back to the solar panel, seek out goeffs on this forum, he's the man
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Old 22 February 2009, 06:02   #3
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Generally, most solar panels come with a reverse diode built it, what this does is prevent your battery from tryung to charge the solar panel, i.e. the charge can only pass from the solar panel to the battery and not the other way.

So, in practical terms, if your panel has one already then you should do no damage by leaving it connected all the time. Ask the people where you got the panel form if it has one.

It is possible to fit an external diode, but you will get a 0.7v drop across it, so your charging will be affected, the makers of the panles allow for this in the design.
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Old 22 February 2009, 12:17   #4
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you could put a resistor in the cable coming from the panel, that would only let the current go one way and not back to the solar panel, seek out goeffs on this forum, he's the man
You mean a DIODE
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Old 22 February 2009, 12:25   #5
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http://www.maplin.co.uk/Module.aspx?ModuleNo=98358

this is the soalr panel that i have.. it says it has a built in diode but it still blew up??
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Old 22 February 2009, 13:27   #6
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TBH i wouldnt worry about it too much, just sling it in the hedge!
A 1.5 watt panel is next to useless anyway, the output will be 1.5 watt when the sun is shining at perfect 90 degrees to the panel and at a solar radience of 1kw/Msquare.
If you get 1/4 watt max on an average day for 6 hours you will be lucky, running the engine for a 10 minutes will do more.
my dad had one in his camper to charge the battery when it was sat idle, the alarm only takes a few milliamps but it couldnt even make up for that
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Old 22 February 2009, 15:59   #7
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I agree - solar panels are pretty crap. I have a 10W fitted and it hardly does anything. Of course in the summer it will give me a few amps a day but my bilge pump won't need it then!!!

As has been said 10 mins of engine running is worth a whole day of sun.

Smaller yachts use solar panels quite a bit but all they really do is keep the batteries from self discharge.
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Old 22 February 2009, 17:49   #8
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I agree - solar panels are pretty crap. I have a 10W fitted and it hardly does anything.
Codders! Where's the logic in that?
Of course it doesn't, it's only 10watts flat out!

That doesn't mean solar panels are crap. It's kinda like having a 1amp alternator on your car and claiming alternators are crap.
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Old 22 February 2009, 18:44   #9
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Our local Tesco has a 40kw solar panel array. Wow 40kw - I could easily run my house on that. In the 3 years they have had it fitted they have generated about 50,000kwh. That works out at about 5,000. It cost 2 million to install - and uses hundreds of panels each one as big as a car!!!

To me that is crap.

Solar panels have their place - in remote areas where laying normal power isn't an option and current usage is very low. For example at a remote resevoir for monitoring equipment etc.

A wind generator on a boat makes more sense in the UK. Problem is they will put out too much power for a RIB.
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Old 23 February 2009, 04:06   #10
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Codders! Where's the logic in that?
Of course it doesn't, it's only 10watts flat out!

That doesn't mean solar panels are crap. It's kinda like having a 1amp alternator on your car and claiming alternators are crap.
But If ALL car alternators were the size of a tall ship sail and 16% effecient like tescos solar panels then you would say they were crap!
The ones that heat water are far more effecient and the way to go for a house, not much god for charging a battery though.
Now a wind generator on a rib! theres a thought, it would pump out some power at 30 knots
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