Instructables
Connecting Multiple Solar Panels

There are 3 ways to connect solar panels; parallel, series, and a combination of parallel and series. The first way I am going to talk about is parallel because this is probably the most common way that panels will be connected. For this example I am showing you connecting panels that are for a 12 volt system.  This is how the panels that I have built in my other instructables are connected, and feed my solar charge controller.

In this first image there are 3 solar panels.  If you look at the arrows along the white and red lines they are showing the direction of flow. The white line is the negative connection, all 3 panel negative wires are just simply tied together and to the wire that runs back to the negative connection on the charge controller.

The red line is the positive connection to the panels.  You will see a symbol that looks like a triangle pointing down at a horizontal line.  That symbol is for a diode, also known as a blocking diode.  What this diode is doing is only allowing the positive electrons to flow in only one direction. When looking at this symbol the triangle points in the direction of flow, when looking at the diode in your hand there should be a colored line around one end of it.  This line represents the line in the symbol that the triangle is pointing to.  The non-colored end would be the “in” side, and the end with the colored line around it would be the “out” side. By installing these diodes on each panel it stops the electrons from going back into other panels. Diodes also use up a small amount of voltage, so don't go crazy and put to many in or you will to low to use.

If you look below the panel to the left you can follow the red arrows from the panel down and make a right turn to the diode. Then they continue through the diode and down the line to the end where they would be connected to a solar charge controller.
 
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graphixv10 days ago

What type of circuit would you need to build in order to be able to switch the panels from series to parallel? I'm going to have 2 100 watt 12 volt panels. I'm planning to add an AC inverter to supply power to the house which requires them to be in a series for 24 volts. But, I already use one panel with a 12 volt back up battery system that I want to keep as-is, which means I'll need to be able to switch them to parallel to provide 12 volts to the charge controller/batteries.

rover41926 days ago
dear sir, I have lived off grid over 10 years. I have run into a situation that no one, including me ,can seem to figure out. Would you be interested in hearing my solar / wind dilemma
vinz3nt1 month ago

Hi,

Thanks for the clear explanation.
I was wondering, I don't use a lot of diodes and I have some IN4001, IN4002 and IN4003 diodes lying around (I think the only difference is the voltage). Are these sufficient?

Thanks!

evert.pitout2 months ago

Hi

I have a 5W PV Solar Power Panel 12V Battery Charger Boat Marine, 5Watt Trickle Charge CAR and 12V KIT Offer ISTA-BREEZE® i-500 Small WIND GENERATOR + Charge Controller.

Will this be sufficient to run 15 to 20 KwH household per day?

kalefranklin (author)  evert.pitout1 month ago

no. you need a lot more generation and storage before you even come close to your power needs. if you are using 20 KwH per day then you need to be producing more than that amount and store it so you have power at night.

gphat6 months ago

my GTI has MPPT function. Is there any lost when some of panel is shaded if I dont have diode in panel

kalefranklin (author)  gphat1 month ago

depending on the quality of the MPPT it may have a diode internally. you would have to do some research to know for sure.

lelegriccioli5 months ago

So what is the advantage of putting them in parallel?

kalefranklin (author)  lelegriccioli1 month ago

putting them in parallel lets you keep the voltage the same and increase the amperage. if you have a 12v system, and two 12v panels that produce 1 amp in series you will have 24v at 1 amp. if you put those panels in parallel you would get 12v at 2 amps. amperage is what pushes power into a battery or powers a system of some kind.

vaddieg1 month ago

Bypass diode serves the similar purpose to blocking diode. It protects the shadowed cell from reverse current

davisbr97 months ago
(removed by author or community request)
kalefranklin (author)  davisbr96 months ago

yes, that is correct. if you have taken any electrical training this is something that you should be learning in at the beginning of your training, or online. that website gives you a good start into series and parallel circuits.

timeman21 year ago
Thanks for the info. Would you spec a certain size diode for a 12v system? I'm sure that would depend on the total amps, correct?

The diode will drop about .6 volts. Multiply this times the maximum current from the panel to get the wattage dissipated by the diode. So if you have 10 amps from the panel, it would be 6 watts for the diode. Then the diode should be rated for the maximum panel output voltage.

Petebob1 year ago
Thank you for writing up a very clear and concise summary of connecting together solar panels.

I'm sure many will find this helpful.