New to solar power which MPPT do i buy?

Collapse
X
 
  • Time
  • Show
Clear All
new posts
  • Sunking
    Solar Fanatic
    • Feb 2010
    • 23301

    #16
    Originally posted by superhuman
    Ive also been thinking because i dont want to run 2 diffrent controllers why does it matter if i want to run at 12v? because if i have 7 panels i cant i need atleast 24v and anything that i want to use can just be used via my inverter(10k) as long as it plugs, correct?
    I already answered this question. With 1600 watts of solar panels, you are forced to go 24 volts because charge controllers have a maximum power input limit. Running at 12 volts with 1600 watts of panels requires 2 charge controllers to a common battery.

    As Mike has pointed out you do not need that much power and would just be throwing money away in equipment. In addition all that extra drag and weight would cost you more in fuel, wear, and tear on the RV. Last comment, there is no battery you could install in the RV that can supply enough power to run a 5000 watt inverter. You would be well advised to get a much smaller more efficient unit.

    My educated guess is you use less than 1 Kwh per day in the RV. If you were to drive or run the engine at least once a day for an hour, you would not need any solar as th eengine alternator can easily generate that amount of power. With solar would only take 300 to 500 watts of solar panels assuming you park in the scalding sun with clear veiw of the horizon from dawn to dusk.
    MSEE, PE

    Comment

    • superhuman
      Junior Member
      • Mar 2013
      • 13

      #17
      Remember that this is a 40ft long rv i have ALOT of space i actually have a ATV inside which i will take out and easily weight over 1000pounds. And i decided to go with a PURE sine wave inverter 5000wat/10000 peak. I truly belive i will use alot of power with 2 gaming desktop's etc tvs and electric showers. Do you have any ideas how many batteries exactly i will need? Dont take into account the RV stuff i know my expenses for my rv and i dont want to include them as they are not part of this project.

      For me i personally feel its cheap i currently have this budget with the stuff ive found:
      1.6k watt of power solar panels(7) $1300
      80a Outback controller $600
      5000watt pure sine wave inverter $500
      Wiring fuses etc $150
      My budget for this project is $4k i currently have left over $1500 just for batteries. How many should i get if i want to run a 24v system with this set up?

      Comment

      • superhuman
        Junior Member
        • Mar 2013
        • 13

        #18



        What do you think about these batteries for my 1.6k watt panels(7) ?

        Comment

        • Naptown
          Solar Fanatic
          • Feb 2011
          • 6880

          #19
          Originally posted by superhuman
          Remember that this is a 40ft long rv i have ALOT of space i actually have a ATV inside which i will take out and easily weight over 1000pounds. And i decided to go with a PURE sine wave inverter 5000wat/10000 peak. I truly belive i will use alot of power with 2 gaming desktop's etc tvs and electric showers. Do you have any ideas how many batteries exactly i will need? Dont take into account the RV stuff i know my expenses for my rv and i dont want to include them as they are not part of this project.

          For me i personally feel its cheap i currently have this budget with the stuff ive found:
          1.6k watt of power solar panels(7) $1300
          80a Outback controller $600
          5000watt pure sine wave inverter $500
          Wiring fuses etc $150
          My budget for this project is $4k i currently have left over $1500 just for batteries. How many should i get if i want to run a 24v system with this set up?
          Well with a single charge controller you can only use 6 of those panels. Two strings of 3 panels in series. The 7th cannot be made to work here with unequal strings of panels. Get a cheap controller and use that to charge the 12V stuff.
          So if you go an AGM battery you will need a minimum of a 236AH- 590AH battery bank
          If flooded lead acid you would need a 590AH battery bank to stay within the charge rates for the batteries.
          At those sizes you should be looking at 2-6V batteries and put in series.
          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

          • superhuman
            Junior Member
            • Mar 2013
            • 13

            #20
            Originally posted by Naptown
            Well with a single charge controller you can only use 6 of those panels. Two strings of 3 panels in series. The 7th cannot be made to work here with unequal strings of panels. Get a cheap controller and use that to charge the 12V stuff.
            So if you go an AGM battery you will need a minimum of a 236AH- 590AH battery bank
            If flooded lead acid you would need a 590AH battery bank to stay within the charge rates for the batteries.
            At those sizes you should be looking at 2-6V batteries and put in series.
            When you say 263ah-590ah do you mean per battery or in total, i was looking into buying these batteries:


            I really dont want a cheap controller i got my eyes on the outback flexmaster 80a and i want to run 24v, are you also saying that its not possible to run 7 panels of this controller correct?

            Comment

            • Naptown
              Solar Fanatic
              • Feb 2011
              • 6880

              #21
              In total for the battery bank. Now the problem comes in is that those are 12V batteries so you will be running 3 strings in parallel of 2 batteries each. This will rapidly degrade the expensive batteries. To prevent uneven charge and discharge batteries should always be in series. Search the forum for batteries in parallel. never a good idea.

              with an uneven number of panels the charge controller will not be able to track to the MPP on the array with any reliability or consistancy. The odd panel might just as well be thrown away for all the good it will do. That's why I suggested a cheap controller ( MPPT to charge the 12V stuff) If you use a PWM controller you will lose over 1/2 the output of the panel.
              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

              • superhuman
                Junior Member
                • Mar 2013
                • 13

                #22
                Originally posted by Naptown
                In total for the battery bank. Now the problem comes in is that those are 12V batteries so you will be running 3 strings in parallel of 2 batteries each. This will rapidly degrade the expensive batteries. To prevent uneven charge and discharge batteries should always be in series. Search the forum for batteries in parallel. never a good idea.

                with an uneven number of panels the charge controller will not be able to track to the MPP on the array with any reliability or consistancy. The odd panel might just as well be thrown away for all the good it will do. That's why I suggested a cheap controller ( MPPT to charge the 12V stuff) If you use a PWM controller you will lose over 1/2 the output of the panel.
                But the outback is a great MPPT controller right? this ist good eh? What about if i go with 4 panels of 240 watt each for a total of 940watt @ 12v would you mind telling me what i should buy such as(please be specific):
                Amount of batteries~
                Specific MPPT controller.

                Comment

                • superhuman
                  Junior Member
                  • Mar 2013
                  • 13

                  #23
                  Originally posted by superhuman
                  But the outback is a great MPPT controller right? this ist good eh? What about if i go with 4 panels of 240 watt each for a total of 940watt @ 12v would you mind telling me what i should buy such as(please be specific):
                  Amount of batteries~
                  Specific MPPT controller.
                  Also if i use lets say i get 3 diffrent cheap mppts would i be able to use my 5000watt inverter to connect to all these seperate systems?

                  Comment

                  • russ
                    Solar Fanatic
                    • Jul 2009
                    • 10360

                    #24
                    Originally posted by superhuman
                    Also if i use lets say i get 3 diffrent cheap mppts would i be able to use my 5000watt inverter to connect to all these seperate systems?
                    Generally cheap mppt units are not mppt except in name.
                    [SIGPIC][/SIGPIC]

                    Comment

                    • Naptown
                      Solar Fanatic
                      • Feb 2011
                      • 6880

                      #25
                      What I said was you cannot use 7 panels on the outback controller. you would end up with two strings of 3 and one string of 1 If you put 4 panels on one string you will be over the max voltage. No matter how you slice it you can use 6 on a controller. Use the outback and keep the 7th panel as a spare would probably be the best thing.
                      As far as specific battery bank size you have not given near enough information on daily loads or locations to begin to tell you what specific size to get. I gave you ranges based on the solar array not use.
                      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

                      Working...