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HELP - 100W 12V vs 175W 24V solar panel - HELP

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  • HELP - 100W 12V vs 175W 24V solar panel - HELP

    Hello everyone,

    I would like to setup a solar panel to power up my reef aquarium LED which use around 110W or 10A @ 12V DC and charging my Deep Cycle battery (600AH)

    I just bought a 100W panel from Costco and a 30A charge controller . This panel had 18.5 Vmpp, 5.42 Impp

    My brother also gave me a 175W panel from BP Solar (model BP 175B), this panel had 35.8 Vmpp & 4.9 Impp

    My question is which one has more power to charge my 12 battery while provide power to my LED?


    Best Regard,
    KEY

  • #2
    The answer is both obvious and obscure. and neither one will work as both are too small to charge that large a battery.
    Obviously the 175W panel has more potential watts. However it is one made for 24V systems.
    I you hook the 175W panel on a PWM charge controller you will lose over half the output.
    Hoook that 80W up and you will get almost everything out of it on a pwm controller.
    So you have 2 choices If you use a pwm controller use the 80W panel.
    If you use a MPPT controller use the 175W panel.
    What is boils down to is you will most likely need to upgrade your charge controller to a mppt if you want the higher wattage or change the battery bank to a 24V bank
    Last edited by Naptown; 11-13-2012, 03:16 PM.
    NABCEP certified Technical Sales Professional

    [URL="http://www.solarpaneltalk.com/showthread.php?5334-Solar-Off-Grid-Battery-Design"]http://www.solarpaneltalk.com/showth...Battery-Design[/URL]

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

    [URL="http://www.gaisma.com"]www.gaisma.com[/URL]

    Comment


    • #3
      Originally posted by key5000 View Post
      I would like to setup a solar panel to power up my reef aquarium LED which use around 110W or 10A @ 12V DC and charging my Deep Cycle battery (600AH)
      Just how many hours per day do you run this 120 watt light? (10 amps x 12 volts = 120 watts, not 110)
      Where are you located?
      What time of year do you run this light?

      Once you answer those 3 questions we can tell you what it will take. But be prepared because you will not like the answer.
      MSEE, PE

      Comment


      • #4
        Originally posted by Sunking View Post
        Just how many hours per day do you run this 120 watt light? (10 amps x 12 volts = 120 watts, not 110)
        Where are you located?
        What time of year do you run this light?

        Once you answer those 3 questions we can tell you what it will take. But be prepared because you will not like the answer.

        1- I want to run the LED for around 6-10 hours every day (more is better). If needed, I can reduce the LED watt to 50W.
        2- I'm in Southern California
        3- As much as I can from solar, every day for 365 days

        The key is I just want to reduce my electric bill therefore I'm going to solar

        Comment


        • #5
          Originally posted by Naptown View Post
          The answer is both obvious and obscure. and neither one will work as both are too small to charge that large a battery.
          Obviously the 175W panel has more potential watts. However it is one made for 24V systems.
          I you hook the 175W panel on a PWM charge controller you will lose over half the output.
          Hoook that 80W up and you will get almost everything out of it on a pwm controller.
          So you have 2 choices If you use a pwm controller use the 80W panel.
          If you use a MPPT controller use the 175W panel.
          What is boils down to is you will most likely need to upgrade your charge controller to a mppt if you want the higher wattage or change the battery bank to a 24V bank
          Here is what I did over the weekend:

          1- Connect 175W/24v and 12v battery to charge controller. The display show panel input 12.8V @ 4.6A
          2- Connect 100W/12v and 12v battery to charge controller. The display show panel input 12.8V @ 5.4A

          Which one of above setup will speed up time to charge the battery?

          When connect my LED light to charge controller, the display show the load is around 10A.

          Comment


          • #6
            Originally posted by key5000 View Post
            1- I want to run the LED for around 6-10 hours every day (more is better). If needed, I can reduce the LED watt to 50W.
            2- I'm in Southern California
            3- As much as I can from solar, every day for 365 days

            The key is I just want to reduce my electric bill therefore I'm going to solar
            That is not going to happen. You are going to pay much more for what you take off the grid.

            OK Let's say you are in LA, light wattage = 120 watt x 8 hours per day = 960 watt hours/day

            Panel wattage required = 420 watts = $840
            Battery Capacity @ 12 volts = 400 AH, at 24 volts 200 AH = $1000
            MPPT Charge Controller = 40 amps = $400

            Now here is the kicker if you buy a good quality battery it last about 5 years at best then needs replaced. Just in battery cost alone you will be paying roughly $0.60/Kwh. Now look and see what that mean ole POCO charges you.
            MSEE, PE

            Comment


            • #7
              Originally posted by key5000 View Post
              Here is what I did over the weekend:

              1- Connect 175W/24v and 12v battery to charge controller. The display show panel input 12.8V @ 4.6A = 58 watts
              2- Connect 100W/12v and 12v battery to charge controller. The display show panel input 12.8V @ 5.4A = 69 watts

              Which one of above setup will speed up time to charge the battery?

              When connect my LED light to charge controller, the display show the load is around 10A.
              None of the above, you can only use one of the panels and need a lot more panel wattage, plus a MPPT charge controller rather than the PWM controller you have now. You will need to loose one of the panels and buy more matching panels for the one you keep. You will also need to replace your PWM controller with a MPPT controller. You pretty much have to start over.
              MSEE, PE

              Comment


              • #8
                Originally posted by Naptown View Post
                So you have 2 choices If you use a pwm controller use the 80W panel.
                If you use a MPPT controller use the 175W panel.
                What is boils down to is you will most likely need to upgrade your charge controller to a mppt if you want the higher wattage or change the battery bank to a 24V bank
                Actually, with the Imp values of the panels being fairly close (4.9 to 5.4) and with the higher voltage panel being the one with the lower current, then as long as your (new) MPPT controller could handle an input voltage of around 100 volts (add the Voc of the two panels and then multiply by 1.25) then you could put the panels in series and get another 40% in current over what you would get from the 175 watt panel alone with the same controller.

                And finally, the fourth choice: If you just use the PWM controller, you can put your two panels in parallel to get almost twice the current of the 80 watt panel alone. You will be wasting more than half of the output of the 175 watt panel, but since you have it already, give it a try. (Note that you may need to put a blocking diode in series with the 80 watt panel to keep the 175 watt panel from backfeeding it when the controller is not pulling current to charge the battery.) The normal rule of thumb is that you should not parallel panels which more than 5% difference in Vmp, nor put panels in series with more than a 5% difference in Imp, but in this situation you may be able to get away with it.

                That still leaves you way short on panel power for the load (current and hours per day) you are trying to drive, though.
                SunnyBoy 3000 US, 18 BP Solar 175B panels.

                Comment


                • #9
                  OK, OK, OK

                  Base on my current equipment (100W/12v panel; 175W/24V panel; charge controller; 1 battery 60AH); how many watt and hours I can use off from solar and battery output?

                  Comment


                  • #10
                    Your 100W panel will run the light about 2 hours a day.
                    NABCEP certified Technical Sales Professional

                    [URL="http://www.solarpaneltalk.com/showthread.php?5334-Solar-Off-Grid-Battery-Design"]http://www.solarpaneltalk.com/showth...Battery-Design[/URL]

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

                    [URL="http://www.gaisma.com"]www.gaisma.com[/URL]

                    Comment


                    • #11
                      Another questions:

                      If I purchase a new MPPT to use with 175W panel and 12V battery, will I get FULL 175W for my 12V battery?

                      If this is true then my 60AH battery will get full charge faster, right?

                      Comment


                      • #12
                        Originally posted by key5000 View Post
                        Another questions:

                        If I purchase a new MPPT to use with 175W panel and 12V battery, will I get FULL 175W for my 12V battery?

                        If this is true then my 60AH battery will get full charge faster, right?
                        You will get 95% of the full actual output of the panel, which will in turn be perhaps 80% of the nominal 175 watts measured in ideal conditions.

                        And yes, it will charge your 12 volt battery about twice as fast as the same panel with a PWM controller.

                        But at that power level, you could buy a second panel to put in parallel for less than you would pay as a premium for the MPPT controller.
                        SunnyBoy 3000 US, 18 BP Solar 175B panels.

                        Comment


                        • #13
                          Originally posted by key5000 View Post
                          Another questions:

                          If I purchase a new MPPT to use with 175W panel and 12V battery, will I get FULL 175W for my 12V battery?

                          If this is true then my 60AH battery will get full charge faster, right?
                          Yes but a 60 AH battery discharged at 10 amps or a C/6 rate means you only get about 60 to 90 minutes use per day. Go any more than that and you destroy the battery. Everything you have is grossly undersized to do what you want to to. Your battery is too small to handle a 175 watt panel. You will be charging it at a C/4 rate. You will boil the electrolyte out the first day.
                          MSEE, PE

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                          • #14
                            I though that if I'm using 175W panel with MPPT then I can power my 12V 50W LED light while charging the battery? Am I right?


                            Can I use MPPT 10A or 20A for my 175W panel?

                            Comment


                            • #15
                              Originally posted by inetdog View Post
                              You will get 95% of the full actual output of the panel, which will in turn be perhaps 80% of the nominal 175 watts measured in ideal conditions.

                              And yes, it will charge your 12 volt battery about twice as fast as the same panel with a PWM controller.

                              But at that power level, you could buy a second panel to put in parallel for less than you would pay as a premium for the MPPT controller.

                              Some low end MPPT controller cost around $50 for 10A or $90 for 20A (no display) that is what I'm planning to buy. Will it has the same performance as premium one which cost $200-$300? what it the different beside LCD display?

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