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Solar panels for charging 24V trolling motor system

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  • Solar panels for charging 24V trolling motor system

    I have a two battery (Excide 27 MDC, with MCA 730, RC-160 and Amp Hr-20) for a 24V trolling motor. I am putting the boat in a dry slip and will have to set up a solar charging system for the two batteries as no other way to charge them. I will normally use the boat maybe every 3 days.

    I assume two separate panels of (100-200 watts) with controllers?

    What do I need and suggestions?

  • #2
    Yes two systems. Panels you will have to be carefully in choosing to charge a 24 volt battery. Lower wattage panels are almost exclusively for 12 volt batteries. You will need Grid Tied Panels which operate at higher voltages which is a good thing because $/watt cost is 1/2 to 1/4 that of battery panels but start at 200 watts. You must have at least a 72 cell panel with a Vmp of 36 volts minimum. Those are going to be at least 200 watts.

    As for charge controllers you have two options of PWM or MPPT. A MPPT i smore expensive but makes a 200 watt panel a 200 watt system. MPPT will make a 200 watt system into 130 watts or less. If you go PWM you only want to use a 72-cell panel with 36 Vmp. Any larger cell count and you will get less than 130 watts from a 200 watt panel.

    For MPPT operating into a 24 volt battery is 200 watts / 24 volts = 8.3 amps or a 10 amp controller.

    For PWM Input Current = Output current. A 200 watt 72-cell panel generates at best 5.5 amps.

    Either way with 200 watts of 72-cell panels into 24 volt battery is a 10 amp controller.

    So if you are using the boat every 3-days; why do you think you need solar or any charging system?
    Last edited by Sunking; 03-30-2016, 03:03 PM.
    MSEE, PE

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    • #3
      I do not have "a 24V battery". I have two separate 12V batteries paired up to run the 24V trolling motor and that is why I thought two separate 12v solar panels wired to each separate battery would work.

      Both batteries are in the front and from the plug ins I would put in for the panel to the battery would only be 2-3 feet of wire.

      The trolling motor will run down and the deep cycle trolling motor batteries have to be charged or no trolling motor. They are not hooked to an onboard charging system off my outboard.

      After some reading here, I think I need two 100 watt solar panels and two 10 watt controllers. However, I may have it wrong.

      Is that right and which ones do you recommend?
      Last edited by hharke; 03-30-2016, 04:42 PM.

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      • #4
        Originally posted by hharke View Post
        I do not have "a 24V battery". I have two separate 12V batteries paired up to run the 24V trolling motor and that is why I thought two separate 12v solar panels wired to each separate battery would work.

        Both batteries are in the front and from the plug ins I would put in for the panel to the battery would only be 2-3 feet of wire.

        The trolling motor will run down and the deep cycle trolling motor batteries have to be charged or no trolling motor. They are not hooked to an onboard charging system off my outboard.

        After some reading here, I think I need two 100 watt solar panels and two 10 watt controllers. However, I may have it wrong.

        Is that right and which ones do you recommend?
        So what is with the Title?

        Solar panels for charging 24V trolling motor system
        Two 12 volt batteries can be configured for either 12 or 24 volts. Wired in parallel, they are 12 volts, wired in series they are 24 volts. Which is it?

        Really makes no difference if I understand you correctly. So you only need one system either configured as 12 or 24 volts. Earlier I thought you had two systems, but it looks like you only have one.
        Last edited by Sunking; 03-30-2016, 05:45 PM.
        MSEE, PE

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        • #5
          I have a similar set up, 2 X 12 volt 109 amp hr FLA's, and a 24 volt trolling motor, easy to charge a 24 volt bank with a 200 watt Grid tie panel, just need a single quality MPPT controller and you are set. It's perfect for something you only use every few days. stay away from 12 volt systems and charge the batteries in series.
          4X Suniva 250 watt, 8X t-105, OB Fx80, dc4812vrf

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          • #6
            To clarify, it is a 24V trolling motor powered by two 12V batteries wired in series.

            "200 watt Grid tied panel, just need a single quality MPPT controller and you are set"

            Ok in english this time please.

            What is a grid tie panel?

            The 10 amp controller is good?

            I see different materials, single or double panels etc and not sure what is what. 200 watt panels seem to be 60x30 inches or more also. I am going to have to unhook it, take it off the boat and replace it when I come back in so size and handling could be an issue.

            Anyone have a link to ones for sale that will work on a 21 ft boat?

            This is all new to me. Do not mind spending the money, but do not want to blow up the batteries or me.



            thanks
            Last edited by hharke; 03-30-2016, 08:23 PM.

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            • #7
              yes., refer to my above post reply, 2X109 AH batteries for 24 volts. I think some Lowes have Grid tie panels, they are higher voltage panels made for grid tie but are also very nice for 24 volt Plus systems. they are the least price per watt and many have 20Plus year warranties. with a nice MPPT controller and a single panel you will be set. If your use changes in the future you could always add another panel for daily use. However if you have grid avail, I would use an AC smart charger for the best battery life.
              4X Suniva 250 watt, 8X t-105, OB Fx80, dc4812vrf

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              • #8
                Looks like lowes does not have much and has discontinued most.

                Am I stuck with the 3 ft by 5 ft panels (200 watt) if I want one panel?

                do I need a 12V or 24V panel?

                Comment


                • #9
                  Originally posted by hharke View Post
                  Looks like lowes does not have much and has discontinued most.
                  You're not going to find this at Lowe's or Home Depot stores. Home Depot has a few Grape Solar panels available online but there are much better places to find them,
                  do I need a 12V or 24V panel?
                  You need at least 72 cells in series. That's usually a single grid tied panel. Do NOT use a 60 cell panel. If you find a "great deal" on a 60 cell panel you'll need two of them.

                  Comment


                  • #10
                    Mount the large, fragile panel to the dock, maybe a post mount, something to keep it out of the way of damage.
                    use a Anderson connector to mate/disconnect when you dock the boat, and the panel will charge it,
                    Mount the MPPT charge controller in the boat, connected to the batteries, and it will retain it's settings, and when the PV panel is
                    plugged in, will start charging if there is sunlight.
                    Parts:
                    PV panel 200 - 300 watt size, At least 35V output (Vpmax)
                    Mount, to attach the panel to. (roof, pole top, side of building.....)
                    Anderson Connectors ( 1 pair, 10 - 20A rating) For PV disconnect
                    MPPT solar charge controller (mount in boat)
                    [300W at 30V charging = 10A] I suggest Morningstar SunSaver 15 Amp MPPT Solar Charge Controller (about $200)
                    Wire it to the batteries with a 15A fuse, set the controller to match the battery type (flooded, AGM, GEL) and hope you don't
                    need to use the boat 2 days in a row, because the battery may need 2-3 days to fully recharge depending on your local sun conditions.


                    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


                    • #11
                      You need a total of 72 cells (the squares on the solar panel) to charge your 24V battery bank. You can either get that with one 72 cell (24V nominal) solar panel, or wiring two 36 cell (12V) solar panels in series, just like you did with the batteries. The Kyocera KD140 or 145 is very popular with boaters, and can ship by UPS or FedEx. The problem with one 72 cell panel is you probably won't find one locally, so will have to order it online. They are too big to ship by UPS, so will have to go by truck, which will likely cost at least $250 to ship. So while the panel may be less expensive than buying 2 smaller panels, the total cost to get 1 to the boat may be more than two smaller ones. Two smaller panels may also be easier to handle than one big panel.
                      Solar Queen
                      altE Store

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                      • #12
                        Cannot mount any panels to the dock. This is a dry slip where the boat is lifted out of the water and put onto 4 high racks. I have to either lay it on the deck or hang it on the side of the T Top frame and remove before going out.

                        So let me see if I have this correct.

                        I will either need one huge 72 cell (24V) panel of 200-300 watts or two 36-60 cell 100 watt 12 V panels in series

                        MPPT solar charger (20 amp)

                        15 amp inline fuse

                        Anderson connectors

                        Did I get it right?
                        Last edited by hharke; 03-31-2016, 08:33 PM.

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                        • #13
                          Originally posted by hharke View Post
                          I will either need one huge 72 cell (24V) panel of 200-300 watts or two 36-60 cell 100 watt 12 V panels in series
                          MPPT solar charger (20 amp)
                          15 amp inline fuse
                          Anderson connectors
                          Did I get it right?
                          That's about right. Make sure the MPPT controller is rated for the voltage you'll be seeing, but with both the above arrangements you won't be near max input voltage of any common MPPT.

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