how many diode amps will support a 20 volt solar panel ?

 

http://www.avdweb.nl/solar-bike/pv-panels/bypass-diodes.html

 

Unless it is a very small panel it will crush most diodes, especially the glass body types.

If you want to know how many amps the diode need to handle, it might help to tell us how many amps the panel can provide.

Ultimately when you are finished there would be no way your system would ever pass a code inspection with home made unlisted, untested components.

 

another gentleman built his own solar panel catching 18.88 volts using 3.5 amp schottys diode , he powers his lights . the panel i built is catching 20 volts . when i hold my multimeter to jones plug it reads 20 volts for a few minutes then just keeps dropping . i have used at 12 volt deep cell battery and a 750watt continous inverter powering a 500 watt space heater. it works! but why does my panel keep losing that much power , that fast when it not in use ?

 

...when i hold my multimeter to jones plug it reads 20 volts for a few minutes then just keeps dropping...

I don't have any explanation of why that would happen, but it does not sound good.

 

Voltage will drop as the panel gets hotter. How much drop are you seeing?

 

dont know if im writing in the right place , this is new to me also . it holds at 19 to 20 volts for a min or two then slowly drops to 15 . my diode doesnt look right tho , it says rectifier diode , is their a difference between rectifier or diode or are they the same? my panel is 2fx4ft with 36 cells with the diode inside with a plexi glass cover . jones plug from panel to 12volt deep cell then to an inverter. it works ! i can run anything with enough batteries but i need my panel to keep the 19 to 20 volts or its to weak to charge my battery. thanks for any help

 

A diode is a diode is a diode... "rectifier" diode would mean it can pass a large amount of current, exactly how much would depend on it's rating. We could check that for you if you can see any sort on number on that specific diode.

A Schottky diode may also come in a rectifier form for large current. It's main attribute is a much reduced voltage drop, in the range of 0.2 volts where a conventional silicon diode drops 0.7 volts or more.

A diode will typically fail shorted or open. A short would not make the voltage drop (it would be very constant as it's now directly connected), open would look give you no voltage out. Can you measure the panel output before this diode? Does it look good there?

If the panel has been in the sun for a few hours, then you put your meter on it and see this drop after a few minutes then it is not a heat effect.

I've never had to troubleshoot a solar panel like this, but I would suspect something is open inside the panel giving you a "ghost" of a voltage that bleeds off into the meter. If you have a 12V light bulb and hook that to the panel I would suspect the voltage would drop immediately.

If by "dont know if im writing in the right place" you mean the forum, it is fine to place it right here. We see it. <grin>

 

... I would suspect something is open inside the panel giving you a "ghost" of a voltage that bleeds off into the meter. If you have a 12V light bulb and hook that to the panel I would suspect the voltage would drop immediately.

I'm inclined to agree that this is somehow a measurement anomaly. If your panel is in steady-state operation (under load) when you attach the meter, and then you observe this voltage sag while nothing has really changed in the panel circuit, I really can't see how it could be "real".

 

i missed a step , THE CHARGE CONTROLLER .

 

I was told my multimeter should have said RUN , FIRE ! anyaway , do i keep my 3amp diode in my 20 volt panel with 36 cells rated 3 amps a cell OR do i go with a 4 amp diode with a 4 amp charge controller ? bulbs are fine but id like to run a 500watt space heater for 8 hrs . im guessing ill need 24 volts because a 12 volt pulls to much at the start up , 3000 watt inverter because a 1500 with 750 watt continous doesnt last long at all without beeping and a bigger charge controller . how much would be enough ?

 

No one has mentioned the 'meter' yet.

I have had multimeters give me some very strange readings. I know, on the cheaper import types, that DC voltage readings will change with any change in the output voltage of the meters' batteries.

Take your readings again with fresh batteries in the meter. VERIFY your results/readings.

You never want to run electronic devices at 100% capacity during NORMAL operation. The 100% capacity rating is should be your MAX., not your normal mode of operation.

3 amps output thru a 3 amp diode is considered operation at 100% capacity. Got it?