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Connecting Solar Panels Together

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How to Connect Solar Panels Together

solar powerConnecting solar panels together is a simple and effective way of increasing your solar power capabilities. Going green is a great idea, and as the sun is our ultimate power source, it makes sense to utilize this energy to power our homes. As solar power becomes more accessible, more and more homeowners are buying photovoltaic solar panels.

However, these photovoltaic solar panels can be very costly so buying them over time helps to spread the cost. But the problem then becomes how do we connect these extra solar panels together to increase the voltage and power output of what’s already there.

The trick here when connecting solar panels together is to choose a connection method that is going to give you the most energy efficient configuration for your particular requirements. Connecting solar panels together can seem like a daunting task when you first start to look at how it should be done, but connecting multiple solar panels together is not that hard with a little thought. Wiring solar panels together in either parallel or series combinations to make larger arrays is an often overlooked, yet completely essential part of any well designed solar power system.

There are three basic but very different ways of connecting solar panels together and each connection method is designed for a specific purpose. For example, to produce more output voltage or to produce more current. Solar panels can be electrically connected together in series to increase the voltage output, or they can be connected together in parallel to increase the output amperage. Solar pv panels can also be wired together in both series and parallel combinations to increase both the output voltage and current to produce a higher wattage array.

Whether you are connecting two or more solar panels, as long as you understand the basic principles of how connecting multiple solar panels together increases power and how each of these wiring methods works, you can easily decide on how to wire your own panels together. After all connecting solar panels together correctly can greatly improve the efficiency of your solar system.

Connecting Solar Panels in Series

The first method we will look at for connecting solar panels together is what’s known as “Series Wiring“. Connecting solar panels together in series is used to increase the total system voltage. Solar panels in series are generally used when you have a grid connected inverter or charge controller that requires 24 volts or more. To series wire the panels together you connect the positive terminal to the negative terminal of each panel until you are left with a single positive and negative connection.

Solar panels in series add up or sum the voltages produced by each individual panel, giving the total output voltage of the array as shown.

Solar Panels in Series of Same Characteristics

connecting solar panels together in series
 

In this method ALL the solar panels are of the same type and power rating. The total voltage output becomes the sum of the voltage output of each panel. Using the same three 6 volt, 3.0 amp panels as above, we can see that when they are connected together in series, the array produces 18 volts (6 + 6 + 6) at 3.0 amps, or 54 watts (volts x amps).

Now lets look at connecting solar panels in series with different nominal voltages but with identical current ratings.

Solar Panels in Series of Different Voltages

solar panels in series with different voltages
 

In this method all the solar panels are of different types and power rating but have a common current rating. When they are connected together in series, the array produces 21 volts at 3.0 amps, or 63 watts. Again the amperage remains the same at 3.0 amps but the voltage output jumps to 21 volts (5 + 7 + 9) .

Finally, lets look at connecting solar panels in series with completely different nominal voltages and different current ratings.

Solar Panels in Series of Different Currents

solar panels in series with different currents
 

In this method all the solar panels are of different types and power rating. The individual panel voltages will add together as before, but this time the amperage will be limited to the value of the lowest panel in the series string, in this case 1 amp. Then the array will produce 19 volts (3 + 7 + 9) at 1.0 amp only, or only 19 watts out of a possible 69 watts available reducing the arrays efficiency.

We can see that the solar panel rated at 9 volts, 5 amps, will only use one fifth or 20% of its maximum current potential reducing its efficiency and wasting money on the purchase of this solar panel. Connecting solar panels in series with different current ratings should only be used provisionally, as the solar panel with the lowest rated current determines the current output of the whole array.

Connecting Solar Panels in Parallel

The next method we will look at of connecting solar panels together is what’s known as “Parallel Wiring“. Connecting solar panels together in parallel is used to boost the total system current and is the reverse of the series connection. By parallel wiring panels you connect all the positive terminals together (positive to positive) and all of the negative terminals together (negative to negative) until you are left with a single positive and negative connection to attach to your regulator and batteries.

When you connect solar panels together in parallel, the total voltage output remains the same as it would for a single panel, but the output current becomes the sum of the output of each panel as shown.

Solar Panels in Parallel of Same Characteristics

connecting solar panels together in parallel
 

In this method ALL the solar panels are of the same type and power rating. Using the same three 6 volt, 3.0 amp panels as above, the total output of the panels, when connected together in parallel, the voltage output would remain the same at 6 volts, but the amperage would increase to 9.0 amps (3 + 3 + 3), or 54 watts.

But what if our newly acquired solar panels are non-identical, how will this affect the other panels. We have seen that the currents add together, so no real problem there, just as long as the panel voltages are the same and the output voltage remains constant. Lets look at connecting solar panels in parallel with different nominal voltages and different current ratings.

Solar Panels in Parallel with Different Voltages and Currents

connecting solar panels together
 

Here the parallel currents add up as before but the voltage adjusts to the lowest value, in this case 3 volts. Solar panels must have the same output voltage to be useful in parallel. If one panel has a higher voltage it will supply the load current to the degree that its output voltage drops to that of the lower voltage panel.

We can see that the solar panel rated at 9 volts, 5 amps, will only operate at a maximum voltage of 3 volts as its operation is being influenced by the smaller panel, reducing its efficiency and wasting money on the purchase of this higher power solar panel. Connecting solar panels in parallel with different voltage ratings is not recommended as the solar panel with the lowest rated voltage determines the voltage output of the whole array.

Then when connecting solar panels together in parallel it is important that they ALL have the same nominal voltage value, but it is not necessary that they have the same ampere value.

Connecting solar panels together to form bigger arrays is not all that complicated. How many series or parallel strings of panels you make up per array depends on what amount of voltage and current you are aiming for. If you are designing a 12 volt battery charging system than parallel wiring is perfect. If you are looking at a higher voltage grid connected system, than you’re probably going to want to go with a series or series-parallel combination depending on the number of solar panels you have.

But for a simple reference in regards to how to connect solar panels together in either parallel or series wiring configurations, just remember that parallel wiring = more amperes, and series wiring = more voltage, and with the right type and combination of solar panels you can power just about any electrical device you may have in your home.

For more information about Connecting Solar Panels Together in either series or parallel combinations, or to obtain more information about the different types of solar panels available, or to explore the advantages and disadvantages of using solar power in your home, then Click Here to order your copy from Amazon today and learn more about designing, wiring and installing off-grid photovoltaic solar electric systems in your home.

Some high quality solar panels you may be interested in which can be connected together and used in solar arrays.


373 Comments » for Connecting Solar Panels Together
  1. Gareth Adams says:

    Hi, I am looking to maximise my simple camper van solar set up. At the moment this is 2 x 100w panels, basic charge controller and single 12v 100a battery. Already thinking that a MMPT controller is preferable? Am I right in thinking that in low light the output voltage could drop below that of the battery and charging will stop… so wiring the panels in series will be best to keep the voltage up and so keep them charging for longer? Thanks

    • Photovoltaic solar panels require sunlight (irradiance) to generate power. The 100 watts power rating of your PV panels is the maximum power they “could” produce at an irradiance level of 1000W/m2 (full sun) and at an operating temperature of 25oC. Since these ideal conditions are not always typical for real PV panels, their actual performance is usually about 85 to 90 percent of this on a good day. You are correct that as light level decreases from this ideal value (cloudy day, early morning, late night) the output power reduces significantly as lower irradiance means a lower charging current.

      For a simple stand-alone battery charging system consisting of a charge controller and a battery, the panels will deliver power at a voltage close to the battery voltage. Charge controllers regulate the flow of current into and out of the connected batteries as well as providing protection against battery overcharging and deep discharging, etc. They also include low voltage disconnection if the solar voltage falls below some value, usually about 11 V preventing reverse currents at night.

      Connecting your panels in series would indeed increase the voltage to 24 volts (2 x 12V) providing your controller accepts this DC input value plus about 25% extra for VOC conditions. 12 volt batteries need about 14.4 volts for charging at a constant current. An MPPT controller is clearly better than a standard charge controller as it will operate the PV panels close to their maximum power point (MPP), rather than at a voltage determined by the batteries, thus extracting considerably more solar power and improving efficiency but they are more expensive.

  2. joe says:

    best charging current is always find your C10 rating of your battery and multiply it by 10%. what ever is the the 10% value, that will be the required amount of Isc that needs to be produced by your PV panel. for your 310w panel your Voc will be about 44.6V and Isc of 9.02amps, i would say connect it in parallel. all 3 panels.

  3. joe says:

    hi there, ive been having this question for quite a while now. its in regards to connecting solar panel in series. i fully understand the rule of connecting t what i dont understand or i am still confused about is why? we have a controller that will regulate the voltage and make sure that the battery is charged with the recommend battery charging voltage. so what are we doing when we are wiring our strings in series???? is it just to carter for the voltage drop and to ensure that the output charging current is successfully delivered to the battery??? or is there another rule to determine how many panels we have to connect in serries????

  4. Anthony Riziki Fondo says:

    Hi guys thanks but I connected 4 200watts panels with a highbrid inverter, connected them I parallel with 3 150A batteries yet I have no maximum power what could be be problem

    • As I keep answering the same question: insolation, temperature, efficiency, cabling, orientation, positioning, etc. A panels wattage is the manufactures standard test conditions (STC) rating and NOT a “real world” rating

  5. Archie says:

    I have 3 solar panels @310 watts each and 3kv mppt inverter plus 2 200ah batteries. …how do I conet the panels? Series or parallel?

  6. Darlington says:

    How do I connect 2x300watts solar panels, 2x12v batteries, 24volts rated inverter and a 40amp rated charge controller

  7. Jeff Murray says:

    Hi there gentlemen, many thanks for a great simplified article.
    My proposed (off-grid) solar array of 8 panels to be wired in parallel, will need (I’m told) to have either a blocking diode or by-pass diode for each panel. I have a MPP 40 Amp charge controller that can handle the voltage of the panels in parallel, but not in series.
    The panels specs are:
    Nominal Power 72.5 watts each
    Voltage at PMAX 66.6 V
    Current at MPP 1.09A
    Open Circuit Voltage 88.7V
    Short Circuit Current 1.23A

    Yes, this is only a small 560W set-up to charge 3 x 12V deep cycle AGM batteries.
    Question: Some say I will need both diodes in each panel owing to fluctuating tree shadows. Where is the best placement for the diodes (either or both) and also, will I need fuses as well?
    Note: the panels have no diodes included.
    Any advice will be much appreciated.
    Cheers and thanks, Jeff.

    • Blocking Diodes are used in parallel strings to prevent a reverse current from flowing back through a string at night time from a connected battery, or if one panel has a lower voltage output than the others. Bypass Diodes are used in series connected panels and are fitted across (in parallel) with each panel to prevent hot spot conditions due to reverse biasing of the panel if it becomes damaged, or shaded. Multiple bypass diodes are usually fitted as standard across a number of cells during manufacturing of the panel.

      For your installation as there are no series connections bypass diodes are not required, and if your parallel connected panels are controlled by a charge controller then blocking diodes are not necessary. You can find more information here about Diodes

  8. Gerald says:

    I am looking for small panels that can be embended on roofing tiles

  9. Yona Sibande says:

    I need a help. How can I connect 18 or 20 solar panels with 2 inverters

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