Connecting Multiple Solar Panels

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Introduction: Connecting Multiple Solar Panels

Connecting Multiple Solar Panels

Theses are the Diodes that I use, they are the same ones that are used when building the panels. Find them here.

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.

Step 1:

In this next step you can see that the left panel is covered, let’s say that a tree was blocking the sun from this panel.  If you look below this panel at the red line you will see that there are no arrows coming from the panel to the right hand bend. And if you look to the right of the diode symbol you can see that the arrows have changed direction from the previous step.  This is how the diode works.  The diode is stopping the electrons from pushing their way back to the panel that is not producing power.  If this diode was not in place then the panel not producing could be damaged.  Also you would be losing some efficiency from the other panels because they would be letting power flow through the nonproducing panel as the electrons are trying to reach the negative side of the panel.

Step 2:

In this step I am showing you how to connect solar panels in a series configuration.  For this example we are going to say that the panels are 6 volt panels in a 24 volt system. Looking at the top image, start at the bottom right that is labeled – NEG.  Following this to the left you see that out of the other side of the panel the line is red, this is the positive side. With this being a 6 volt panel, and we need 24 volts we need to increase the voltage. To do this we connect the positive side of the first panel to the negative side of the second panel. There will now be 12 volts coming out of this second panel. Continuing up to the top left panel, there will be 12 volts in and coming out with 18 volts. Continue this through the fourth panel on the top right, there will be 24 volts coming out if this one.  You can also see the blocking diode here; it functions the same way as in the first example to keep from back feeding power into the panels.  These 4 panels wired up in this way work as if they are one large panel that produces 24 volts.  Having one blocking diode is the minimum that is needed in the circuit.

In the lower image the panels are connected in the same manner, positive to negative to reach 24 volts. In addition to blocking diode there are bypass diodes.  The reason for these are to allow power to go around a panel that is shaded by something.  It helps to keep that correct flow of power, not that it won’t flow in the correct way if their not there.

**Personal note** I have not seen any information on about efficiencies of panels connected in series with or without bypass diodes. I have not connected panels in this way either, all my panels are 12 volt and connected to a 12 volt system.

Step 3:

In this step I am showing what happens when a panel is shaded by something such as a tree. You see that the bottom left panel is shaded, so the power follows the path around the blocked panel through the bypass diode. In this configuration you should be getting 18 volts.  This may not be charging a 24 volt system very well, but it will be adding some charge through amperage.  Less is better than none. If you have a higher end charge controller it may be able to use this lower voltage in some form, or maybe able to boost it back to the 24 volts to keep charging. You would need to check the specs on your particular charge controller.

If you do not install bypass diodes, as in the first image on the previous step, I do not see why all panels would stop producing power. They may just produce less power than if there were blocking diodes installed.  This is something that would have to be considered when building a panel system.  Is the loss in power worth the cost of extra diodes?

Step 4:

In this step I am showing a combination parallel and series configuration. In this example we will be using 12 volt panels in a 24 volt system.  The 2 panels at the top of the image are connected in series of each other, and the 2 panels at the bottom are also in series of each other. These 2 rows of series panels are connected in parallel of each other.  So the top row produces 24 volts, and the bottom row also produces 24 volts.  Together both rows provide 24 volts there blocking diodes, then on to the collective point that would run back to the charge controller.  Because each row provides the same voltage, and they are in parallel the total voltage to the charge controller is 24.  The only time the voltages add together is when they are in series, like in each row.  2 panels that produce 12 volts each in series produces a total of 24 volts.  And in this example I also put in the bypass diodes.

Step 5:

In this final step I am showing an example of a shaded panel in a combination parallel and series wiring configuration.  You can see that the top row is unaffected.  In the bottom row the left panel is shaded by a tree.  The top row will be producing 24 volts, the bottom row will only be producing 12 volts. Because of the blocking diodes at the end of each row the 24 volts will not push back into the row producing 12 volts.  You will be losing power because one of the panels are shaded, but they’re not going to back feed. You may still be gaining in amperage even though it’s at lower voltage if the battery needs the charge, or if there is another place for the power to go such as out to lighting or a tool. Again, less power is better than no power from panels.

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56 Comments

I have two solar panels both rated at 200watts each, unfortunately they hav different voltage. One is 36 volts and the other one is 16 volts. can hey work if i connect them in parallel and using a blocking diode for the panel with the lower voltage? do you think it could work with the blocking diode? thanks in advance!

I think you may have misunderstood the purpose of the blocking diode - this is only used to prevent the battery trying to 'power' the solar panels at night (or, to be more accurate, when the output voltage of the panel is lower than the battery voltage). The rule of thumb when connecting solar panels directly to a battery is never connect more than C/10 watts, where C is the capacity of your battery. For example a 110AH battery should never be connected to a panel more than 11W without a solar controller and, if you are using a solar controller, you do not need a blocking diode.

So, assuming you're using a solar controller...

The controller will have a 'maximum system voltage', which however you wire up the panels must not be exceeded e.g. series = 52v (36v + 16v = 52v). If this exceeds your solar controller's spec, the only option you'll have is to wire in parallel. If OK, you then need to look at the 'max power current' value. When connected in series, this will end up being the maximum current flow, irrespective of the power rating of the panels. So, for example, if one is rated at 8A, the other only 5A, you will only ever get 5A at 52V = 260W. Mismatches in current spec when connected in series will effect overall performance.

Parallel wiring in your case will probably be the worst option because, whilst the current will be additive, the overall system voltage will be limited to the lowest voltage panel i.e. 16V so, for example, you'll end up with 5A + 8A = 13A at 16V = 208W, which will inevitably be lower than a connection in series.

If I were you, and because solar controllers are usually a lot cheaper than solar panels, I would buy another solar controller and operate each panel separately.

Mismatched specification panels will always lead to a compromise in performance.

i wanted to cut my three panel portable solar panel so it would fit better on my backpack, but now matter how i connect the terminals that were left, i can't create a circuit. I have included pictures. There are two positive and two negative poles. how are the supposed to be connected? Any advice?

Sorry if this is a duplicate, I posted or thought I did, but it disappeared

My solar panel has 3 wires on it. It is rated: 90watts, 17.9volts, 5.03amps.

Has Black, White and Green wires. Black and White wires have a diode

between them with the top or "band" end on the White wire side. Could you

tell me the correct way to connect this to a charge controller that only has

a "+" and a "-" wire slot on it. Thank You

Direction of positive electrons? All electrons are negative. Positive atomic particles are called protons but only electrons (negative particles of atoms) flow in an electric circuit. Realizing that our culture is to accentuate the positive, eliminate the negative and don't mess with mister in-between, we must all relinquish our prejudices and realize that all of electricity consists of only the negative portion of the atom being pulled and tugged down the entire path of connectivity, while each electron knocks other negative particles of other atoms in, around and about in a forceful manner. Incidentally, the proton and the neutron form the atom's nucleus and the electron spins around the outer edge of that cluster. Electrons in diodes flow the direction from the arrow point into the wider part of the arrow, or for the banded diode they flow into the band and come out the other (bandless) end. The diode is a one way electron valve. The battery (-) is the source of electrons and the battery (+) is the absence of electrons, so therefore electrons flow toward the positive terminal via the external (to the battery) circuit. Negative (always) electrons flow from a battery minus to the battery plus. They flow into the diode symbolic arrow tips and bands and come out the other end of the diode, and only flowing one way.

it just mixed up current and electron flow ?

Positive electrons are called positrons like those in anti matter. Also diodes conduct in both directions. They have an avalanche or reverse breakdown voltage and will have this listed on their datasheet.

best way to full charge a baterry is in parallel connection or series whatever the volt or amp ratings are

HI there. Interesting read. I think I understand the logic. I live on a boat that has 4x Shell SM110-24 (rated output 110w; rated current 3.15A; rated voltage 35V). Becuase of the mast and boom these is often a shadow that passes over one or more of the panels - often leaving the other panels fully exposed to direct light. From what I read the shadow on one panel is likely to be affecting the performance of the whole array. It's almost that I need each individual panel going back to the batteries individually - but thats a lot of wiring. What would be the best set up - series or parallel - and use of blockign diodes to minimise the impact of the shadow on one part of the array?. Cheers.

this is dependent on your battery and controller. but most likely parallel