Should I Connect My Solar Panels In Series Or Parallel
CAN I MIX DIFFERENT SIZE SOLAR PANELS?
A common question asked by many iTechworld customers:
“Can I join one of your 120W Solar Panels with my existing 200W Solar Panel on my roof to get 320W?”
Mixing and matching Solar Panels can be done. In order to get the results you are looking for though you must take all the factors into consideration beforehand. In this blog I will look at the different ways of connecting Solar Panels together to make an array. I will break down the basic fundamentals to give you an idea of what wattage you should expect from your array.
When you are looking to connect Solar Panels produced by different manufacturers together the problem does not come from different manufacturing styles or cell type, it comes from the electrical characteristics of the solar panels. Watts, Volts and AMPS.
There are two ways to wire up Solar Panels. Series and Parallel. Both have their own purpose and applications and both have different outcomes when hooking up Solar Panels of different wattage together.
Firstly lets take a look at connecting Solar Panels in series. Solar Panels are usually connected in series to obtain higher output voltage. This is usually the case with 24v systems.
If we connect 4 x 150w Solar Panels in series the total power is calculated as follows:
Total power = 150W + 150W + 150W + 150W = 600W
However if we were trying to create 620watts of power using different wattage solar panels we would have a different outcome.
Mistakes To Avoid When Charging Batteries With Solar Panel
The most critical mistake to avoid when charging batteries with solar panels is connecting expensive panels and large batteries to a solar power controller and wires that arent calibrated to work with the system.
This error will result in significant drops in efficiency and could result in fire hazards if the parts overheat from being undersized.
Make sure everything works with everything. Keep your solar panel max output voltage well over your battery bank voltage by at least 2 volts. Keep your wires as short as possible to avoid unnecessary efficiency loss.
Choose a charge controller that is either equivalent to your voltage and amperage system values or large enough to accommodate added future panels.
Make sure you install your panels with the best sun exposure. Most online calculations assume five hours of direct sunlight per day. If you place the panels in a shaded location or at a wrong angle to the sun, your production rates will substantially decrease.
Dont underestimate your wattage needs. When you calculate your system needs, dont leave anything out. For example, you shouldnt think about your average wattage needs but rather your maximum wattage needs.
It is much easier to leave charge in the batteries than overdraw from them. However, when you drain a battery system too much, you can damage the batteries, which decreases their life span.
Connecting Solar Panels In Series
Stringing solar panels in series involves connecting each panel to the next in a line .
Just like a typical battery that you may be familiar with, solar panels have positive and negative terminals. When stringing in series, the wire from the positive terminal of one solar panel is connected to the negative terminal of the next panel and so on.
When stringing panels in series, each additional panel adds to the total voltage of the string but the current in the string remains the same.
One drawback to stringing in series is that a shaded panel can reduce the current through the entire string. Because the current remains the same through the entire string, the current is reduced to that of the panel with the lowest current.
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Wire Sizes For Solar Panels In Series Vs Parallel
The wiring diagram is fairly straightforward on this one, so check it out:
For series, at the 57 volts and 9 amps, we can use 10 gauge wire for anything under 70 feet from the panels to the charge controller.In Parallel, we can use 10 gauge wire from the solar panels to the combiner box, but only if the longest wire length is shorter than 24 feet.After the Combiner Box, since our amps ramp up to a little over 27, weve got to step it up to 6 gauge wire but we have to make sure our solar controller is closer than 15 for the 6gauge to be big enough.Also, those lengths dont give us much wiggle room. We REALLY have to try to make the runs as short as possible because if we have much voltage drop, it further decreases what our charge controller has to work with in terms of voltage.Remember, if the voltage of the solar panels is lower than the voltage of the batteries, they cant charge.On both setups, both series AND parallel, 8 gauge wire is recommended from the charge controller to the batteries given we keep that distance under 5 feet, which is pretty feasible as thats good system management anyway.
Breakers for wiring Solar Panels in Series vs Parallel
Now, we need to talk about breakers because we all know that none of this matters if your wires rub through, short out, and catch your camper on fire. Dramatic, yes but lets get to it.
How To Connect Two Solar Panels To One Controller Correctly
Are you planning to purchase or have you already purchased portable solar kits but are slightly baffled on how to connect two solar panels to one battery charge controller? If so, the good news is that there is nothing for you to worry about. The process is not as complicated as you imagine.
In this post, well help you with your concerns about how to connect two solar panels to one controller. Likewise, well discuss the materials youll need to prepare as well as the step-by-step guide on how to carry out the task correctly. Lets keep the ball rolling!
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Can You Add More Solar Panels To Your Existing System
Going with a full installation from the start is always best when installing a residential solar system. Using a solar calculator helps estimate your solar system costs and power needs in order to accurately determine how many panels you should have in your system.
However, if you were limited with your budget, or underestimated your future power needs when you installed your PV panels, you could consider adding more panels to your existing system.
If you are thinking about expanding your solar PV system in the future, you should design your system with that in mind. In order to accommodate more panels in the future, you should have an oversized inverter.
Ensure The Minimum And Maximum Voltage Are Within The Inverter Range
Do not allow the strings you are connecting to the inverter to exceed the inverters maximum input voltage or maximum current, or to fall below its minimum/start voltage.
Ensure that the maximum voltage complies with code requirements in the area where you are designing.
In the U.S., the National Electrical Code caps the maximum allowable voltage at 600V for most residential systems. In Europe, higher voltages are allowed.
Pro Tip: Dont Use STC Values Alone to Determine Voltage Range
We know that voltage is additive in series strings while current is additive in parallel strings. As such, you might intuitively assume that you can determine the voltage of our proposed PV system design and whether it falls within the recommended range for the inverter by multiplying the voltage of the panels by the number in a series string.You might also assume that you could determine the current of the system by adding the current of each parallel string .
However, as we discussed above, since STC values reflect the modules performance under very specific conditions, the actual voltage of the panels in real-world conditions may be quite different.
To ensure that the temperature-adjusted string voltage is within the input voltage window of the inverter it will require a more complicated formula, like the ones below:
An Example of Underperforming PV Systems
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Should I Connect My Solar Panels In Parallel Or Series
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- When solar panels are hooked up in series you connect the minus of one panel to the plus of the next panel.The voltages are summed, but the current remains the same:Putting panels in series is desirable as it keeps the amperage low, and amperage is the key factor in cost of the wire.Now let’s look at panels in parallel. Here all the negatives are connected to each other, and all the positives are connected to each other. So the voltage stays constant and you sum the currents.With a PWM charge controller you’ll want to put the panels in parallel as those devices reduce the voltage to the battery’s voltage and would otherwise waste a lot of power.When using an MPPT charge controller it will have a maximum voltage and current that you can put on any input. You typically put the most panels you can together in series but not so many you exceed the voltage. You repeat that for as many panels as you have and then connect the strings together in parallel.For example, if you had 6 panels with Vmpp= 22.5, Impp=5.75 and an MPPT with 60 volts and 20 amps max then you might arrange your panels into three parallel strings of 2 panels in series.When a panel in a series is affected by shade, it can reduce the voltage of the entire string, reducing the power output of the string.One way around this is to use diodes as shown below:Note that most modern solar charge controllers have blocking diodes built in to prevent draining your batteries at night.
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Mc4 Connectors For Wiring Solar Panels In Series Vs Parallel
MC4 Connectors are the way most solar panels are wired together. Sure, some people just cut off the connectors and splice the wires together and thats fine, but for those of us who like the ease of use of the MC4 connectors, there are a few differences between parallel and series.Solar panels typically have MC4 connectors built onto the ends of their built in wires like this:
And in the following picture, this is how you would be wiring the panels up in series and in parallel using MC4 connectors:
In 90% of installations, when wiring in series, the solar panels can be placed close enough together so that the positive lead of one panel will reach the negative lead of the adjacent panel. This means you wont need extra MC4 connectors to make the inter-panel connections.If that solar panel arrangement works for your setup, youll only need 1 pair of MC4 connectors for the whole series.For Parallel wiring, youll need a pair of MC4 connectors per solar panel you use.
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Newpowa Mc4 1′ Flexible 4 To1 Branch Parallel Connection Set
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Description SLCBL-47:Set of 1ft flexible parallel cable with high quality hard plastic IP65 rated MC4 connectors. For use to direct connect with other Newpowa modules with MC4 connectors for parallel wiring 4 modules. Y connectors will maintain a secure, tight,read more
Overall, whether using series or parallel would depend on how to balance the voltage and amperage so you could achieve the highest output possible. You can check out Newpowa cables connection for some more ideas.
Common Arguments For Parallel Over Series
Recently weve been getting a ton of comments arguing for wiring solar panels in parallel and they always go something like this:I want max solar output from my solar panels and if I wire in series, park under a tree, and get shading on part of my array, It significantly decreases power to the entire array.andI want max solar output from my solar panels and if I wire in series and a panel breaks It significantly decreases power to the entire array.
In our 3+ years of being on the road, neither of these have been a problem.Fortunately, Ive developed a highly-sophisticated strategy for solving both of these problems and still wiring in series and lucky for you, Ive made diagrams for both of them.The first diagram fixes the problem in regards to getting max solar output when your camper is parked near a tree thats causing partial shading to your solar array.
This next diagram fixes the problem in regards to getting the max solar output of an array with a broken panel.
There have been tests done showing how one bad panel or shading on one panel will decrease the output of the entire array. All of that is true Im not debating that.My point is this: If you are TRULY worried about getting the maximum output from your solar panel array park in the sun and maintain your solar panels.
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What Does It Mean To Wire Solar Panels In Series
Just like a battery, solar panels have two terminals: one positive and one negative.
When you connect the positive terminal of one panel to the negative terminal of another panel, you create a series connection. When you connect two or more solar panels like this, it becomes a PV source circuit.
Solar panels are wired in series when you connect the positive terminal of one panel to the negative terminal of another.
When solar panels are wired in series, the voltage of the panels adds together, but the amperage remains the same. So, if you connect two solar panels with a rated voltage of 40 volts and a rated amperage of 5 amps in series, the voltage of the series would be 80 volts, while the amperage would remain at 5 amps.
Putting panels in series makes it so the voltage of the array increases. This is important, because a solar power system needs to operate at a certain voltage in order for the inverter to work properly.
So, you connect your solar panels in series to meet the operating voltage window requirements of your inverter.
Solar Panels In Series Of Same Characteristics
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 from above, we can see that when these pv panels are connected together in series, the array will produce an ouput voltage of 18 Volts at 3.0 Amperes, giving 54 Watts at full sun.
Now lets look at connecting solar panels in series with different nominal voltages but with identical current ratings.
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How Many Appliances Can Be Powered By Portable Solar Panels
The energy consumption on outdoor camping sites would usually be minimal. Energy from the solar panels would be just enough for you to run small appliances such as a 12v camping fan or camping fridge and meet your lighting requirements. Heating appliances will require more energy and can drain your solar battery faster.
Key Electrical Terms To Understand For Solar Panel Wiring
In order to understand the rules of solar panel wiring, it is necessary to understand a few key electrical termsparticularly voltage, current, and powerand how they relate to each other.To understand these concepts, a helpful analogy is to think of electricity like water in a tank. To expand the analogy, having a higher water level is like having a higher voltage there is more potential for something to happen , as illustrated below.
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Wiring Solar Photovoltaic Panels In Series
As we said above, when connecting solar panels in series, we get an increased wattage in combination with a higher voltage.
Such higher voltage means that series connection is more often applied in grid-tied solar systems where:
1) the system voltage is often at least 24 volts, and
2) the solar array output voltage is fed to an inverter or charge controller of a typically higher input voltage compared to off-grid systems.
Connecting in series means joining the positive terminal of a solar panel to the negative terminal of the next solar panel until eventually you are left with one free positive and one free negative terminal of the array, which are to be connected to the input either of the inverter or the charge controller .
When you connect solar panels in series, the total output current of the solar array is the same as the current passing through a single panel, while the total output voltage is a sum of the voltage drops on each solar panel.
The latter is only valid provided that the panels connected are of the same type and power rating.
Lets consider the depicted below solar panels designated for a 12V solar panel system, operating at their Maximum Power Point, while delivering the depicted voltage and current that correspond to this power tracking point.
Scheme of solar panels connected in series
What Its Best For
Solar panels in series are optimal in unshaded conditions. If shade covers a single panel of your series array, it will bring down the whole systems power output. Each panel in a series connection is critical.
Solar panels in series are also best if you need a low-amperage system. To calculate the output power of a solar system, multiply the voltage by the current. If you have a higher voltage system, your amperage will be lower. Lower amperage allows you to use smaller gauge wires which are less expensive and easier to work with.
One important thing to know is that you will need to use an MPPT charge controller when wiring your panels in series. MPPT charge controllers regulate the voltage and current from the solar panels to match the battery banks voltage without sacrificing power. If you use a PWM controller, the battery will pull the total panel array voltage down to match it, and you will lose a lot of power.
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