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  1. #1
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    Solar panels in series or parallel, pro and con

    I need some help with solar panels. I've seen several post says solar panels in series is better than in parallel but haven't been able to get much detail as to why. Any explanation, reference or link will be greatly appreciated.
    Bill & Marsha
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    Quote Originally Posted by wjpatter View Post
    I need some help with solar panels. I've seen several post says solar panels in series is better than in parallel but haven't been able to get much detail as to why. Any explanation, reference or link will be greatly appreciated.
    https://www.renogy.com/learn-series-and-parallel/


    In a nutshell, parallel gives you a higher amperage, which requires a correctly sized wire gauge (read larger); series gives you a higher voltage with the same amperage. This is just like with batteries.

    For my planned install of 6 195w panels on my 320MKS, I'll be using 2 pairs in parallel, and each pair will be parallel with the other pairs to the combiner box. The combiner box will have 3 paid of #6 wire going in to it on the roof, and have 1 pair of 0/2 going down to the charge controller.

    The amperage from each of the pairs is calculated at 32.5 amps and the combined total amperage, going to the charge controller, is 97.5 amps.

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    Site Sponsor JCR GD's Avatar
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    This quote is from the above link and is most important if you ask me (depending of course on where you mostly camp.)

    "The downside to series systems is shading problems. When panels are wired in series, they all in a sense depend on each other. If one panel is shaded it will affect the whole string. This will not happen in a parallel connection."

    So if in series any shading from anything will shut them all down. Not so good when anywhere but wide open skies.
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    @wjpatter
    It also depends on the controller you use. Victron MPPT needs +5v over battery to start. Series gives you higher voltage. Depending on your set up you will want a MPPT controller. Over at the other place there is a solar forum. Also Facebook has the GD solar forum (just do a search). Lots of good reading. BTW when choosing your MPPT controller also look at the PV voltage specification and not just the volts and amps. It can be an expensive mistake and not allow your pannels to run at max performance. MPPT controllers do better than PWM units. Lots of articles and Youtube on why.
    Last edited by powerscol; 01-23-2021 at 09:35 AM.
    2018 Reflection 150 Series 220RK 5th wheel with 6K axle upgrade. B&W 25K OEM Companion, Steadyfast system, 2022 F350 SRW 6.7 King Ranch 8' bed, Trailer reverse lights, rear spare tire holder, storage tube, sumo springs, Victron MultiPlus 12/120/3000, and Solar

  5. #5
    Site Sponsor SolarPoweredRV's Avatar
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    Quote Originally Posted by wjpatter View Post
    I need some help with solar panels. I've seen several post says solar panels in series is better than in parallel but haven't been able to get much detail as to why. Any explanation, reference or link will be greatly appreciated.
    I understand your confusion about wiring in Series or Parallel, however, have you considered the advantages of wiring in both Series AND Parallel?

    You don't give us any details about the number of panels nor any information about the panels you are considering.

    Because there are several types of obstructions that can shade panels on an RV, I would recommend against wiring all your panels in Series because you never know when you are going to have partial shade from an Air Conditioner or trees.

    So now you are left with two choices. Depending on the voltage of your panels (and the voltage of your battery bank) a combination of Series and Parallel might be best.

    In my opinion, unless your panel voltage is twice the voltage of your battery bank you should consider the Series/Parallel route.

    Let me illustrate by explaining how I made the decision on my system (keep in mind that I am running a 24 volt system so voltages on a 12v system would be halved). I installed 4 panels rated at 37 volts. I felt that 37 volts was not high enough to charge a 24 volt system. So, I installed 2 panels in series (yielding 74 volts) and paralleled the two pair of series panels in parallel. When I tied the two pair of panels together in parallel, I still had 74 volts to feed into my Solar charge controller.

    Now, if I were running a 12 volt battery bank, I would probably wired all 4 panels in straight Parallel, feeding 37 volts to my Solar charge controller.

    I hope this example helps...
    David and Peggy
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    Adding additional panels down the road is easier when the system is in a parallel configuration.
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    Site Team traveldawg's Avatar
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    Quote Originally Posted by SolarPoweredRV View Post
    I understand your confusion about wiring in Series or Parallel, however, have you considered the advantages of wiring in both Series AND Parallel?

    You don't give us any details about the number of panels nor any information about the panels you are considering.

    Because there are several types of obstructions that can shade panels on an RV, I would recommend against wiring all your panels in Series because you never know when you are going to have partial shade from an Air Conditioner or trees.

    So now you are left with two choices. Depending on the voltage of your panels (and the voltage of your battery bank) a combination of Series and Parallel might be best.

    In my opinion, unless your panel voltage is twice the voltage of your battery bank you should consider the Series/Parallel route.

    Let me illustrate by explaining how I made the decision on my system (keep in mind that I am running a 24 volt system so voltages on a 12v system would be halved). I installed 4 panels rated at 37 volts. I felt that 37 volts was not high enough to charge a 24 volt system. So, I installed 2 panels in series (yielding 74 volts) and paralleled the two pair of series panels in parallel. When I tied the two pair of panels together in parallel, I still had 74 volts to feed into my Solar charge controller.

    Now, if I were running a 12 volt battery bank, I would probably wired all 4 panels in straight Parallel, feeding 37 volts to my Solar charge controller.

    I hope this example helps...
    I'm afraid I am going to open a whole new can-of-worms, but here goes.... If your panels feed 74 volts to your charge controller and your charge controller feeds 24 volts to you battery(s) then how do you get 12v to your RV systems?

    And why did you choose a 24v battery system versus a 12v battery system (which, to me seems simpler and requires one less device - presumably the one that converts 24VDC to 12VDC)?
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  8. #8
    Site Sponsor SolarPoweredRV's Avatar
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    Quote Originally Posted by traveldawg View Post
    I'm afraid I am going to open a whole new can-of-worms, but here goes.... If your panels feed 74 volts to your charge controller and your charge controller feeds 24 volts to you battery(s) then how do you get 12v to your RV systems?

    And why did you choose a 24v battery system versus a 12v battery system (which, to me seems simpler and requires one less device - presumably the one that converts 24VDC to 12VDC)?
    To get 12 volts for my coach, I simply installed a 24v to 12v DC to DC converter. This supplies all of the 12v systems in the coach.

    Why do I have a 24v system?

    Well there are are good reasons to upgrade your system to a 24v system when you have a large battery bank and a larger Inverter (3000 Watts + ). One of the biggest reasons is the efficiency of the Inverter, the Inverter only needs to increase the voltage by a factor of five for a 24v system versus a factor of ten for a 12v system. Another advantage is that I can use smaller gauge wiring, in my case I used 1/0 wires versus 4/0 wires which are common in 12v systems.

    When you are designing a system, many components like the Solar Charge Controller can be used for either a 12v or 24v system so there isn't any difference in component cost.

    So, if you are going to be installing a large battery bank and a high wattage Inverter, I would recommend everyone to seriously consider upgrading to a 24v system.

    With all of the above being said, the real reason I went with a 24v system is because my Tesla battery modules are 24 volts (nominally). However, if I were to consider building a similar system with 12v batteries, I would definitely design the system as a 24v system.
    David and Peggy
    2019 Ford F350 Lariat, 6.7L Diesel, Dually, Long Bed
    Running with 20k Reese Goosebox (Love It) and Ford Factory "Puck" system.
    Stopping with 8,000 lb Disc Brakes and Titan Hydraulic over Electric Brakes system.
    Powering all this fun with 1200 Watts of Solar, two Tesla, Model S, battery modules, 24 volt Victron Inverter.
    2018 Solitude 310 GK

  9. #9
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    Quote Originally Posted by powerscol View Post
    @wjpatter
    It also depends on the controller you use. Victron MPPT needs +5v over battery to start. Series gives you higher voltage. Depending on your set up you will want a MPPT controller. Over at the other place there is a solar forum. Also Facebook has the GD solar forum (just do a search). Lots of good reading. BTW when choosing your MPPT controller also look at the PV voltage specification and not just the volts and amps. It can be an expensive mistake and not allow your panels to run at max performance. MPPT controllers do better than PWM units. Lots of articles and Youtube on why.
    The Renogy DC-DC converter that I both to charge of the alternator is a 50 amp device that came with a MPPT solar controller with input range to support 12v or 24v input and a temperature probe for the batteries. It has an ignition sense for the alternator that I've tested and find to work ok. I hadn't expected that to be a limitation on the solar port. So given the 50 amp limitation of the controller, I'll probability be looking at 4 to 6 panels.
    Bill & Marsha
    2020 Reflection 320 MKS
    2018 2500HD Silverado 4x4
    Not All Who Wander Are Lost

  10. #10
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    Quote Originally Posted by SolarPoweredRV View Post
    I understand your confusion about wiring in Series or Parallel, however, have you considered the advantages of wiring in both Series AND Parallel?

    You don't give us any details about the number of panels nor any information about the panels you are considering.

    Because there are several types of obstructions that can shade panels on an RV, I would recommend against wiring all your panels in Series because you never know when you are going to have partial shade from an Air Conditioner or trees.

    So now you are left with two choices. Depending on the voltage of your panels (and the voltage of your battery bank) a combination of Series and Parallel might be best.

    In my opinion, unless your panel voltage is twice the voltage of your battery bank you should consider the Series/Parallel route.

    Let me illustrate by explaining how I made the decision on my system (keep in mind that I am running a 24 volt system so voltages on a 12v system would be halved). I installed 4 panels rated at 37 volts. I felt that 37 volts was not high enough to charge a 24 volt system. So, I installed 2 panels in series (yielding 74 volts) and paralleled the two pair of series panels in parallel. When I tied the two pair of panels together in parallel, I still had 74 volts to feed into my Solar charge controller.

    Now, if I were running a 12 volt battery bank, I would probably wired all 4 panels in straight Parallel, feeding 37 volts to my Solar charge controller.

    I hope this example helps...
    My controller is limited to 50 amp output so probably 4 - 6 panels depending on the panels and the amount I allow for derating. I haven't considered the panel voltage output and has to be my learning curve. Question on a different topic. How strong are these panels. The reason I ask is this last weekend I was parked under an oak tree which didn't mean much until the wind blew in the middle of the night and I thought someone was banging on the coach with a hammer. How much concern needs to be put into falling debris with selecting the panel source?
    Bill & Marsha
    2020 Reflection 320 MKS
    2018 2500HD Silverado 4x4
    Not All Who Wander Are Lost

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