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gotwind
Forum Admin
United Kingdom
843 Posts |
 Posted - 02/05/2008 : 18:20:40
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I have recently bought a 12v 55w solar panel.
In the image below, you can see 2 diodes, marked 10A10 or maybe IA10? - 10 Amp I assume.
My question is, are these bypass diodes for partial shading of the panel - it seems so from a volt meter test and me covering sections of the panel with my hand, (I still get 20'ish' volts).
And more importantly do I also require an additional blocking diode and heat sink before the battery? - Schottky has been mentioned for less voltage drop.
Can't get my head around it - Ghurd?
Ben.
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oz_sprog
Starting Member
USA
10 Posts |
Posted - 02/05/2008 : 19:04:31
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I can't answer what the diodes in the image are but for your second point I can give my personal experience.... I had a blocking diode between my 12v panels and the batteries and I found I lost more voltage with the diode than without it.. go figure! Now I have a simple 2 way switch that I turn off at night to stop reverse current, not that reverse current can harm the panels in a 12v system.
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ghurd
Junior Member
USA
304 Posts |
Posted - 02/05/2008 : 21:53:39
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Those are bypass diodes. 10A 1,000V.
If it is going into a 12V system, snip one end of each one. They won't help anything in a 12V system, but if one fails, the PV won't charge.
If you have 2, going in series for a 24V system, there is a tiny chance someday they will help when the battery is very dead.
They have a better chance of helping in a 48V or higher system.
A solar controller will have a built in 'blocking diode' (but probably a mosfet).
If using a windmill type controller, use a blocking diode. The ones in the box would be great if you can unsolder them.
It wouldn't need to be a Schottky. Very minor difference on 3A. If you go with a Schottky, get a 10A in a TO-220 package and use a small heat sink.
G-
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gotwind
Forum Admin
United Kingdom
843 Posts |
Posted - 03/05/2008 : 21:10:20
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Thank you Ghurd and Fungus (via email) for your help.
It is intended for a 24v system with shadowing highly likely in this application.
I will connect a 10 amp diode (same as the bypass diodes shown) on the positive line - it should fit within the housing in the image above.
I don't know why they weren't factory fitted really??
Ben. |
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ghurd
Junior Member
USA
304 Posts |
Posted - 04/05/2008 : 03:10:45
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Most solar installations use solar controllers, so no need for blocking diodes.
Many of the newer installations are higher voltage, and a diode in each panel would have more losses. It would add up if the controller was MPPT.
Serious PVs do not have them. Small PVs for use where a controller normally wouldn't be used may have them.
There is some debate about if they really do any good. They certainly do here, where it is cloudy for weeks on end.
G-
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Solar panel help
