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A rectifying Diode on my solar panel?

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redeye
Master Marine Consultant

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3476 Posts

Initially Posted - 12/02/2008 : 12:30:16

Dave indicated the solar panel might be pulling power from my battery at night. I am surprised the solar panel is not designed to prevent electrical "backflow".

Q >> 1. TESTING 2. SOLUTION

1. connect solar panel and umphmeter on positive in the dark. (use itty bitty light to look at meter) If I see power in volts going to solar panel then...

2. Wire in the following
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=6A-1KV&vReviewShow=1&vReviewRand=2439936#reviews

It that right?

Thank You

Ray in Atlanta, Ga.
"Lee Key" '84 Catalina 25
Standard Rig / Fin Keel

Edited by - on

Prospector
Master Marine Consultant

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Canada
3159 Posts

Response Posted - 12/02/2008 : 12:43:03

Ray,

I think that sounds like the right idea - that diode will control flow by acting as a one-way valve. Most solar panels have this built in. Read your fine print. Mine does, and I have tested to be sure it is working.

The parts I outlined in the other thread will do that as well (for 1000X the money), however they will also give an output showing the battery voltage, Amps, etc. And they would be able to handle the larger flow rates generated by the alternator, AC charger,and solar all running at once. They will also control the rate of charge such that the batteries don't charge too quickly. The only thing they don't do is isolate the batteries from each other, which a bettery isolator/combiner would do.

My knowledge of this stuff is very minimal, however from what I know you have to be very careful about sizing that diode. For solar it can be sized according to your panel size, however if you have any other chargers that may be running on the same circuit, you want to be sure you aren't going to just blow that valve away.

I would suggest you start by connecting your solar etc. in the daytime so you know what current is running through it when things are working. You can put anything solid (dark) over the panel to see what happens when the lights go out, or simply turn the panel face down on a settee cusion, and put something medium-heavy on it (Push down on it) to block light - then you don't have to work in the dark to see what happens.

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redeye
Master Marine Consultant

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3476 Posts

Response Posted - 12/02/2008 : 13:01:52

Right, Check the output of the solar panel in the daylight. The rect diode I selected is rated for 6 amps up to 1000v dc and I think the panel is outputting <3 amps, like a trickle charger, but I hafta check that.

No other chargers or alternators.

Thanks for the help.

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newell
Navigator

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USA
113 Posts

Response Posted - 12/02/2008 : 14:34:20

Actually you can check the situation out in the day time as well. Just put the diode in the circuit backwards (long leg toward negative) and measure the amps being produced. Then, reverse the diode and measure again. With the diode in its blocking position (long leg toward positive) there ought to be a sharp drop in amps.

You can probably get by with an even smaller diode rating as the amps produced by a 10 watt panel are very small.

newell

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redeye
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3476 Posts

Response Posted - 12/03/2008 : 11:50:10

Thanks Newell, I thought the amps on a solar panel would be nill, but did not remember the specs. I'd thought the 6 amp rec. diode might have had some voltage drop when pushing through. I might need as small a diode as I can get away with. I am just guessing the larger diode would require more of a voltage drop than a smaller one.

Thanks

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Dave Bristle
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Djibouti
10005 Posts

Response Posted - 12/03/2008 : 14:44:30

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by newell
 ...You can probably get by with an even smaller diode rating as the amps produced by a 10 watt panel are very small...<hr height="1" noshade id="quote"></blockquote id="quote">...like 10w / 15v = .67 amp.

Edited by - Dave Bristle on 12/03/2008 14:50:34

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