Announcement

Collapse
No announcement yet.

Solar panel voltages too low for CC to work properly

Collapse
X
  • Filter
  • Time
  • Show
Clear All
new posts

  • Solar panel voltages too low for CC to work properly

    Trying to setup a small panel to maintain my 4wd dual batteries using a victron mppt 75/15 which connects directly to my starter batt. The isolator links both batts when there is a charger connected to starter batt terminals.
    I first tried a small 40w (21voc, 17max volts) panel.
    but the cc was stuck in bulk and would never go up to absorption even after 2hours in sunlight. I tried this when both batteries were linked and at 12.7v and at another time 13v in morning, the previous day i charged them using the AC-DC charger.

    However the cc did go into absorption with a single battety within a minute.

    Not sure what i should do? What size/type of panal should i get?

    Also my CC wont work unless PV V is 5V+ battV. There after only 1V+ is needed. I would like to know why they do this?

    thanks

  • #2
    I'd guess one of your dual batteries is sick. 40w of PV is not very much
    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


    • #3
      Originally posted by Mike90250 View Post
      I'd guess one of your dual batteries is sick. 40w of PV is not very much
      Both batteries are quite young. I went 40w as it's only to keep topped up and nothing else. What would be the minimum wattage i should get? Is 21voc and 17.5max power voltage good for this CC or do i need a higher voltage panel?

      Comment


      • #4
        Originally posted by Jman View Post

        Also my CC wont work unless PV V is 5V+ battV. There after only 1V+ is needed. I would like to know why they do this?

        thanks
        I've been researching charge controllers recently and this question came up for me also when looking into the Victron Smartsolar 75/15 and other Victron products.
        I posted a few questions on the Victron forum and these were the responses I got for the "Vbat + 5V?".
        (Also keep in mind, company is based in Netherlands so the English fluency won't be spot on.)


        "Well it seems the +5Vdc setting is a negative point, but of course that is something we did on purpose.
        I know other brands advertise with this and it can be confusing for endusers, but if you have the theory behind it i guess you agree that starting with a PV voltage at the battery voltage doesn't make sense.

        Why?, well in order to be able to charge a battery you need to have power in combination with a high(er) voltage.
        A solar panel generates a voltage, but as soon as you start taking power from it the voltage drops.
        So having a charger sitting on the exact same voltage as the battery doesn't make sense as you cannot generate a charge current towards it (technically spoken, the powerpoint is lower then the battery voltage.)
        So, if we would activate the charge controller at that battery voltage point anyway, because we then would appear to be "most efficient" it will not charge the battery at all.
        Even worse, The fact that the charge controller is ON then means it needs power to be able to run itself.
        So instead of charging the battery you risk it would deplete the battery more then you charge.
        Overall, its better to wait a little bit longer in the morning that the PV panels do get above 5Vdc above the battery voltage as then the charger can actually start right away with putting power in the battery.

        After this, the panel is "loaded "so the voltage is already lower then the open clamp voltage.
        At that state the controller keeps on pulling energy as long as it can, so untill the point when the panel voltage is at Vbat+1Vdc.
        This results that the charger continues to actually charge as long in the evening as it can."



        Originally posted by Jman View Post
        What would be the minimum wattage i should get? Is 21voc and 17.5max power voltage good for this CC or do i need a higher voltage panel?
        Also a similar question I had. This was the response to that.

        "it uses the actual PV voltage at a certain time to decide to switch on.
        For this set up the charging number of hours is more limited then working on a higher PV voltage (panels in serial connection)"


        The setup being referred to is: 100 watt 12V panel --> Victron Smartsolar 75/15 --> 12V AGM battery

        For full discussion:
        http://disqus.com/by/gretagremlin/
        If the responses don't show, you can go to view in discussion below the appropriate question.

        Comment


        • #5
          Originally posted by Greta Gremlin View Post

          I've been researching charge controllers recently and this question came up for me also when looking into the Victron Smartsolar 75/15 and other Victron products.
          I posted a few questions on the Victron forum and these were the responses I got for the "Vbat + 5V?"............
          To recharge a battery, you need a voltage higher than the battery & high enough to run the overhead of the charge controller.

          to reliably charge a 12V battery, you need at least 20Vmp PV panels. Many MPPT controllers want to see battery charge voltage x 1.5 for the solar before their circuitry becomes effective.

          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


          • #6
            Do this, take the controller out and connect directly to the panel. Once batteries are charged up, you can keep them at 100% with a 10 watt panel. My guess is you just got impatient and you have a low battery and one day was not enough to charge both batteries.

            If it were me I would give it a day or two.
            MSEE, PE

            Comment


            • #7
              Originally posted by Sunking View Post
              Do this, take the controller out and connect directly to the panel. Once batteries are charged up, you can keep them at 100% with a 10 watt panel. My guess is you just got impatient and you have a low battery and one day was not enough to charge both batteries.

              If it were me I would give it a day or two.
              I haven't purchased any solar equipment yet, the setup was only hypothetical. Still trying to figure out which equipment is compatible for a small setup. It will be based on a lead acid 12V battery and should not exceed 100 AH. Likely will experiment first with a 12V 7AH battery during the day to see what can and can't be done with panel without draining battery power. Read through the stickies also, they have been most useful.


              Originally posted by Mike90250 View Post

              To recharge a battery, you need a voltage higher than the battery & high enough to run the overhead of the charge controller.

              to reliably charge a 12V battery, you need at least 20Vmp PV panels. Many MPPT controllers want to see battery charge voltage x 1.5 for the solar before their circuitry becomes effective.
              The 12V panel nominal --> MPPT controller -->12V battery seems to be the first thought for many newcomers who want a small setup. I've read many people whose controllers fell short of expectation because they didn't know about the high voltage difference needed between panel and charge controller. That's significant for putting together an efficient system and surprised how rarely it is mentioned from what I've read on solar. I am currently trying to figure out if this is common among all solar controllers OR just MPPT OR only certain brands/models.

              So if an MPPT controller needs around 1.5 more voltage than battery, then 12V nominal panels are not ideal for a 12V battery since Vmp range is 15-19.

              Since 12V panels are likely more affordable
              x2 12V panels wired in series for 24V would work but there are the shading issues with panels ran in a series.
              or
              x1 24V panel though less affordable

              Other than this, were there anymore workable solutions for making best use of:
              ​​​​​​​??? solar panel --> MPPT --> 12V battery

              Comment


              • #8
                Originally posted by Mike90250 View Post

                To recharge a battery, you need a voltage higher than the battery & high enough to run the overhead of the charge controller.

                to reliably charge a 12V battery, you need at least 20Vmp PV panels. Many MPPT controllers want to see battery charge voltage x 1.5 for the solar before their circuitry becomes effective.
                Thats depressing. The whole camping world of panels don't look to go over 20vmp. Probably because the regulators are toys.


                edit: so what about 19.5vmp on victron mppt 100/50 CC? You said at least 20 so that suggests to me its still too low. Can't know until i try but these particular panels cost alot as they fold up nicely.
                Last edited by Jman; 06-11-2018, 06:22 AM.

                Comment


                • #9
                  Originally posted by Jman View Post
                  Thats depressing. The whole camping world of panels don't look to go over 20vmp. Probably because the regulators are toys.


                  edit: so what about 19.5vmp on victron mppt 100/50 CC? You said at least 20 so that suggests to me its still too low. Can't know until i try but these particular panels cost alot as they fold up nicely.
                  You can get away with "battery" panels to charge a 12volt battery but it is not the ideal plan due to needing a higher voltage. The lower voltage usually means your batteries will probably not last as long because they will never get back up to 100% SOC.

                  Comment


                  • #10
                    Originally posted by Greta Gremlin View Post



                    Since 12V panels are likely more affordable
                    x2 12V panels wired in series for 24V would work but there are the shading issues with panels ran in a series.
                    or
                    x1 24V panel though less affordable

                    Other than this, were there anymore workable solutions for making best use of:
                    ​​​​​​​??? solar panel --> MPPT --> 12V battery

                    Where are you living that 12 volt panels are "more affordable" than 24 volt panels? The only thing that is costlier would be shipping for one or two of the large format 24 volt panels. There are 24 volt panels in the 190 watt range that are 32" x 65" shipping would likely be less on those. If any 60 cell or 72 cell grid tie type panels are available locally, shipping prices are a moot point.

                    The main reason that 12 volt panels are more expensive is the fact that they aren't manufactured in the huge quantities that grid tie panels are. 12 volt panels are selling for around a dollar a watt and up everywhere I look. Grid tie panels are typically selling for 50 cents a watt and under. Shop around, they can be found for as low as 30 cents a watt.
                    2.2kw Suntech mono, Classic 200, NEW Trace SW4024

                    Comment


                    • #11
                      Contacted Morningstar and asked about the voltage difference required between controller and battery for the Sunsaver MPPT 15amp (Another controller I've been looking at.).
                      Here's their response:

                      "Our listed battery voltage is 7-36. Start up is +1V higher, so 8V to start the controller. Hope that helps."


                      Originally posted by littleharbor View Post
                      Where are you living that 12 volt panels are "more affordable" than 24 volt panels? The only thing that is costlier would be shipping for one or two of the large format 24 volt panels. There are 24 volt panels in the 190 watt range that are 32" x 65" shipping would likely be less on those. If any 60 cell or 72 cell grid tie type panels are available locally, shipping prices are a moot point.

                      The main reason that 12 volt panels are more expensive is the fact that they aren't manufactured in the huge quantities that grid tie panels are. 12 volt panels are selling for around a dollar a watt and up everywhere I look. Grid tie panels are typically selling for 50 cents a watt and under. Shop around, they can be found for as low as 30 cents a watt.
                      In Southern Illinois, but I've been comparing panel prices from Web searches without shipping costs.
                      If grid-tie panels will be more affordable then that seems a much better way to go.
                      Where would you recommend looking at grid tie panels?
                      Also, would there be any extra steps needed for using grid-tie panels for offgrid?

                      Comment


                      • #12
                        Try Craigslist. Availability varies by location buy if only looking for a handful of panels it may be your best bet. You might find a local solar contractor with some odds and ends in their back stock.

                        As to what you need for grid tie panels, An MPPT controller to step down the voltage. . The Victron controller you have mentioned will work for you. The 100 volt, open circuit maximum will limit you to strings of two 60 cell panels in series or, one to three 72 cell panels in parallel for your 12 volt system, Voltage wise your best bet is 60 cell panels. You need a 150 volt max. controller to get more flexibility with 72 cell panels. If you're not limited to 12 volt system you, again, have more flexibility with 24 volts.
                        2.2kw Suntech mono, Classic 200, NEW Trace SW4024

                        Comment


                        • #13
                          Originally posted by SunEagle View Post

                          You can get away with "battery" panels to charge a 12volt battery but it is not the ideal plan due to needing a higher voltage. The lower voltage usually means your batteries will probably not last as long because they will never get back up to 100% SOC.
                          Its enough to turn me off camping panels. Not paying big bucks unless they fully charge. The whole camping world of panels and regulators is governed by salesmen.

                          Comment

                          Working...
                          X