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How to connect a diode on parallel solar panel connection? Answered

I am making a foldable solar charger. I will have 3 panels connected in parallel, for a total rating of 5 volts at 1.5 amps. This will connect directly to a USB boosting converter for a maximum output of 5V at 1 amp for charging or powering a USB device. No batteries will be connected. Can I just use a diode on the + wire where it connects to the USB charger or do I really need one on each panel? Thanks for any help!

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user
icengBest Answer (author)2014-03-01

You need three DIODEs otherwise one cell will be slightly higher voltage and pass current in reverse through the other panels

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Stevemills04 (author)iceng2014-03-01

i do know series from parallel. I have three panels, rated for 5 v at 500 ma each. When i attach 3 diodes, will my voltage drop be 0.45 x 3 or just 0.45? With only 5 volts, it would hurt to lose 1.35 volts.

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iceng (author)Stevemills042014-03-01

Sorry, needed to know your electric IQ as your home page is mostly empty.

Just 0.45V x1 for all three and only if all three are pulling 1 amp each

But you will probable only loose 0.38V x 1 at the lower current.

BTW if you have two amp meters you can test the system without the diodes and not hurt anything just put amp meters in place of the diodes and watch what happens. You can get diodes here at 14 cents each.

http://www.jameco.com/webapp/wcs/stores/servlet/Pr..

If you really want ten less voltage drop 0.04V drop here is a fun circuit.

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Stevemills04 (author)iceng2014-03-01

Thanks iceng, I truly appreciate the help. I am a newbie. Made some small solar chargers but only with one panel. If I only lose .38 to .45V in total after putting a diode on each panel, thats good. I was worried that I would lose .45 per diode per panel, which would hurt. Since I will not have anything connected permanantly such as batteries, are the diodes still 100% required?

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iceng (author)Stevemills042014-03-01

No, it shouldn't hurt anything, but if a leaf or cloud covers one panel.

That panel turns into a sucking resistor which may cause a full current halt

until the leaf or the cloud moves away.

With diodes only the panel that has shade stops current delivery, leaving power by the remaining panels to continue at the current that the sun feeds them.

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mpilchfamily (author)2014-03-01

It's more common to place the diode on the negative lead but the posative lead will work too.

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user

But i can just use one diode on the lead between the usb and panels vs a diode on each panel?

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iceng (author)Stevemills042014-03-01

Do you know parallel from series ?

And use low forward o.45 voltage drop like 1N5817 schottky diodes

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