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  • Solar Panel Voltage

    What is the difference between the volt ratings on different panels. Is a higher voltage better than a lower voltage panel? Whey would you want a lower or higher voltage panel? And what are the advantages or disadvantages of having a lower voltage panel instead of a higher voltage panel while both panels have the same amount of wattage output? Thanks

  • #2
    i am just a marketer, so i just supply sample advise. what you would like to use solar panels would depend on which voltage panels. if you charge for 12V equipment, you may choose low voltage panels; if you charge for 24V or 48V equipment, you need to choose high voltage panels.

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    • #3
      Originally posted by wika_boy View Post
      What is the difference between the volt ratings on different panels. Is a higher voltage better than a lower voltage panel? Whey would you want a lower or higher voltage panel? And what are the advantages or disadvantages of having a lower voltage panel instead of a higher voltage panel while both panels have the same amount of wattage output? Thanks
      The advantage of higher voltages is smaller wire size - easier to install and saves a few bucks. The advantages of low voltage panels is not having to deal with high voltage. 12 V is pretty safe stuff, a string of 240V is a different matter.

      I've opted for 48VDC panels and strings of 4, which under the right conditions can add up to over 400V!! My inverter is able to deal with high voltage inputs, and I'm comfortable working with 400VDC, since I do that in my job anyway.

      Most new inverters are made to have higher voltage inputs - it is simple to string several panels in series and use smaller wires to connect them to the inverter. In the old days inverters took 12V or 24V inputs exclusively. In fact many of the newer inverters reach their maximum efficiencies around 240VDC input.

      Lawrence
      Lawrence Lile, PE

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      • #4
        Hi

        Does Higher panel wattage and inturn reduced current affect the charging time of the battery??

        for 12V battery system shall we choose 17.6V panel??? PLease advice

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        • #5
          Originally posted by moonrathna View Post
          Does Higher panel wattage and inturn reduced current affect the charging time of the battery??

          for 12V battery system shall we choose 17.6V panel??? PLease advice
          Not at all. Charge time of a battery is dependent on the current. However with respect to battery systems the panel voltage selection is selected based on 2 ctiteria: Charge controller type and Battery voltage. For explanation I will only use 12 volt battery systems.

          If you are going to use inexpensive PWM charge controllers you should not use anything higher than a 22 Voc panel which produces !8 Vmp voltage. But PWM charge controllers have a huge flaw, they are very inefficient at 60 to 70% at best. With any linear type voltage regulator the input current = Output current. So if you have a 12 volt panel rated @ 100 watts the Vmp = 18 volts, and Imp = 5.5 amps. Since we know input current = output current the maz output wattage with 100 watts is 12 volts x 5.5 amps = 66 watts. To add insult to injury most of the PWM controllers will accept up to 50 volts on a 12 volt system. So a 100 watt panel is 50 volts @ 2 amps with an output of 24 watts a 75% loss.

          MPPT controllers are true DC-TO-DC converters and able to take advantage of using up to 150 Voc or 135 real working Vmp. So if there was such a thing as a 100 watt panel with 135 volts Vmp @ .75 amps, the output is 12 volts @ 7.9 amps or 95 watts.
          MSEE, PE

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          • #6
            panel voltage and system voltage

            normally, we choose the nearly voltage solar panel for charging battery.
            that's to say, if you have 2x12V batteries, you want to connect them to 12V.
            you have to use 12V solar panels for them.
            if you connect 2x12V batteries to 24V, in this case, 24V solar panels are needed to charge for them.
            (you could use one 24V solar panel or connect 2x12 panels to 24V, that's depend on you), and so on
            Last edited by Mike90250; 07-26-2011, 09:43 AM. Reason: sales links in .sig deleted - Mod
            [COLOR=#000080][B][SIZE=2]Professional solar energy & solutions provider
            [/SIZE][/B][EMAIL="info@do-solar.com"]info@do-solar.com[/EMAIL]
            [URL="http://www.do-solar.com"]www.do-solar.com[/URL][/COLOR]

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            • #7
              Originally posted by dosolar View Post
              normally, we choose the nearly voltage solar panel for charging battery.
              that's to say, if you have 2x12V batteries, you want to connect them to 12V.
              you have to use 12V solar panels for them.
              if you connect 2x12V batteries to 24V, in this case, 24V solar panels are needed to charge for them.
              (you could use one 24V solar panel or connect 2x12 panels to 24V, that's depend on you), and so on


              Just to clear this up. It takes 15V at the battery terminal (16V when equalizing batteries) to give them a full charge. All charge controllers loose a volt or 2 in their circuitry, so you need a PV panel that produces at least 18V, and if you are in a warm area, 20V, to have enough voltage, to properly charge a battery. So a 19V panel is generically called a 12v panel, because it's used for charging 12V batteries. You cannot take a panel, with a 12V output, to charge a 12V battery, it does not have a high enough voltage to "push" power into the battery to recharge it.
              Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
              || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
              || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

              solar: http://tinyurl.com/LMR-Solar
              gen: http://tinyurl.com/LMR-Lister

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              • #8
                Originally posted by Mike90250 View Post


                Just to clear this up. It takes 15V at the battery terminal (16V when equalizing batteries) to give them a full charge. All charge controllers loose a volt or 2 in their circuitry, so you need a PV panel that produces at least 18V, and if you are in a warm area, 20V, to have enough voltage, to properly charge a battery. So a 19V panel is generically called a 12v panel, because it's used for charging 12V batteries. You cannot take a panel, with a 12V output, to charge a 12V battery, it does not have a high enough voltage to "push" power into the battery to recharge it.
                Thanks for the coherent explanations of MPPT vs. PWM controllers - very helpful. For the 12V system above, would the "19V" rated panel be Voc or Vmp? And does this scale linearly for a 24v battery bank (2 ea. 12v, 250Ah VRLA batts. in series) thus needing "36V" panels?

                I have panels that are rated V at Pmax = 30.3v, and Voc = 37.7v. Would these work for a 24v VRLA battery bank? Then I can use a cheap Xantrex C40 charge controller but will need to buy a 24V inverter. This will be used at a summer cabin in the Sierras with no shading, at 7500' elevation, and thus really just for 3 months of the year. How important will equalization of the 2 batteries be in that scenario?

                Thanks, Steve

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                • #9
                  depends on your loads, if you will harvest enough power. If loads are slight, then that panel would be an OK voltage. As the battery tops off, you won't pull as much amps, and the PV voltage can trend a bit higher. But if you are using the batteries heavily, you may not be able to fully recharge, and then you start down the spiral drain of deficit charging.
                  Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
                  || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
                  || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

                  solar: http://tinyurl.com/LMR-Solar
                  gen: http://tinyurl.com/LMR-Lister

                  Comment


                  • #10
                    voltage of the solar panel

                    What is the difference between the volt ratings on different panels.
                    Bascally for each solar cells,its voltage is around 0.5V,so we got 18 solar cells in series,36 48 and 72,so we got the panel voltage is 9v 18v 24v 36v which is for the load of 6v 12v 18v 24v.The output voltage of the solar panel can not be more than 1.5 times of the load.Suggest 1.4 times of the load.


                    Is a higher voltage better than a lower voltage panel?
                    No,depend on the load,as the rules of 1.4 times.
                    PV-solarpanel

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                    • #11
                      Originally posted by WollySF View Post
                      Thanks for the coherent explanations of MPPT vs. PWM controllers - very helpful. For the 12V system above, would the "19V" rated panel be Voc or Vmp? And does this scale linearly for a 24v battery bank (2 ea. 12v, 250Ah VRLA batts. in series) thus needing "36V" panels?

                      I have panels that are rated V at Pmax = 30.3v, and Voc = 37.7v. Would these work for a 24v VRLA battery bank? Then I can use a cheap Xantrex C40 charge controller but will need to buy a 24V inverter. This will be used at a summer cabin in the Sierras with no shading, at 7500' elevation, and thus really just for 3 months of the year. How important will equalization of the 2 batteries be in that scenario?

                      Thanks, Steve
                      Steve
                      The panel or panels you have are 60 cell panels and are really intended for grid tie applications.
                      If you have more than one up to three put them in series and use a MPPT charge controller.
                      If you only have one the voltage may be too low for charging a 24V battery.
                      So what exactly do you have?
                      Rich
                      WWW.solarsaves.net

                      NABCEP certified Technical Sales Professional

                      http://www.solarpaneltalk.com/showth...Battery-Design

                      http://www.calculator.net/voltage-drop-calculator.html (Voltage drop Calculator among others)

                      www.gaisma.com

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