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  • Small Race Boat Solar Proposal

    I am building a small kiteboat for a 750 nautical mile boat race in mid June around the 50th parallel north.
    Mid day sun angle 80 degrees off horizontal.

    Speeds could reach 30 - 35 knots (~35MPH, ~60KPH) day and night, water strikes are common.
    2' - 3' diameter, 50' long logs awash, sea containers, whales, submarines, rocks even, you get the picture.
    It's a tough boat: foam core and many layers of epoxy-fiber.

    I was all keen to build a 100ah lifepo4 pack to fit, encased in polyurethane gel to mitigate impact,
    only to discover they're unavailability in Canada, cost and shock susceptibility...
    12 volt AGM seemed an alternative. Good shock resistance so no polyurethane gel, but heavy.
    I have room for three 100 watt flex panels.
    A PWM controller seems cost and space effective.

    6 hours of "peak" sunshine is the average per day for the area, at that time of year.
    I have excellent panel exposure on deck.
    12 volt, 2 - 5 amp constant draw (10 max) 24/7.
    Race duration: 2 - 5 days with no shore power available.

    Does this sound a reasonable set-up?
    I am about to purchase as my build approaches that stage and June is not far away.
    I could really use some help with this.
    Thank you.

    Draw breakdown:
    1 amp navigation system,
    0.5 - 2 amps auto-pilot,
    0 - 2 amps air blower, .
    0.04 - 5 amp VHF radio,
    0 - 1 amp nav lights,
    0 - 2 amp bilge pump,
    0 - 2 amp spot light,
    Sat and cell phones.
    Last edited by BlueBell; 03-14-2018, 12:12 PM.

  • #2
    So, I was hoping for some dialogue as I had a few more questions.
    Any recommendations on battery brand or type of AGM for this type of application?
    Flex panel recommendations or concerns? I was considering 100 watt panels.
    Any controller comments or recommendations? PWM vs MPPT?
    BlueSeas breaker/switches okay by you?
    Is there too much information in the post above, or too little.
    This forum totes itself as the world's leading and most popular...
    So, what is wrong with my post to garner zero response?

    Comment


    • #3
      I think you are expecting too much from solar. In a boat, all the shadows from stays, masts and sheets, pretty much ruin production. A shadow from a stay, across a panel, can pretty much shut it down. By the time you get enough panels for all the loads, and enough batteries for a couple cloudy days, it's not pretty. Often a top of mast wind turbine is used, even with it's monthly maintenance needs (moving electrical parts in salt water - going to need maintenance)
      Honestly, for 5 days, I'd save all the trouble, and load up on a couple large deep cycle batteries and just bleed them to death. A sacrifice to the Race Gods. Calculate your daily watt hour requirements, x 5 days, and size the battery for that. We've got stickies for these calculations
      https://www.solarpaneltalk.com/forum...-panel-systems.
      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


      • #4
        Thanks Mike for your reply.

        It's a kite boat, there are no masts, stays, sheets or shrouds to block the panels.
        The kite will rarely ever be in a position to block the sun from the panels.

        The boat is small and one 60 pound AGM is more than 10% of the boat weight.
        More batteries is not a very attractive option when flex panels are 4 pounds each.

        A wind generator is not an option I'm afraid.

        I looked at the link you supplied.
        I don't have a zip code, I have a postal code.
        What's a sticky?

        Comment


        • #5
          Originally posted by BlueBell View Post
          Does this sound a reasonable set-up?
          I didn't see anything about battery size in your proposal. I'd plan for 2-3 days of autonomy and then do the rest from solar. That gives you some margin.

          They do ship LiFePO4 batteries, you know. Inverter Supply, for example, has free shipping on Victron 60ah 12V batteries.

          Nothing wrong with AGM batteries. Make sure you provide a vent. They outgas far less than flooded batteries, but they do outgas - which might be an issue if you try to seal them. There are plenty of manufacturers that make waterproof vents for such things.

          Comment


          • #6
            Thank you jflorey2 for your reply.

            100ah, third paragraph, first sentence, post #1.

            Yes, they ship lifepo4 but they don't allow into Canada.

            Would you be so kind as to provide a link to waterproof vents?

            Thanks

            Comment


            • #7
              A PWM controller is not cost effective as it will turn your 300 watt of panels into 200 watts or less. 200 watts of panels using a quality 15 amp MPPT charge controller will do the same.

              Gassing and thermal runaway is a non issue using solar. Silly to think otherwise. With solar the batteries will never be fully charged and and would take more than 24 hours on a commercial charger to become an issue. As for AGM batteries you get what you pay for. As for brands well there are lots of them and for Marine AGM use Rolls as they are the default choice for marine applications. Click this link and select from the chart. With 200 watts of panels using a quality MPPT controller you can support as small as 80 AH up to 150 AH at 12 volts. Or do it your way with 300 watts of panels with a 15 amp PWM controller still limits your battery to the same capacity of 80 to 150 AH. You way will just cost more and add unnecessary weight.

              Keep something in mind please. AGM batteries were invented for military aircraft where spills and extremely rough conditions are every day life. Water, G force, and Inverted is not going to hurt them.
              Last edited by Sunking; 03-14-2018, 07:44 PM.
              MSEE, PE

              Comment


              • #8
                Sunking, thank you for your most informative reply.

                You hit-the-nail-on-the-head addressing weight, reliability, cost and ruggedness as important variables in my application.

                Rolls it is, 100 ah, MPPT and two panels.
                I can add a third panel if sea-trials indicate it necessary... or can I, aren't the panels wired in series for a PMMT?

                I don't need ignition protection ( no explosive gases on board, the blower is for ventilation as the cockpit is enclosed ) so would a marine rated controller/charger be an unnecessary expense?

                Any flex-panel links, controller/chargers links?

                Thanks again.

                Comment


                • #9
                  Originally posted by BlueBell View Post
                  Sunking, thank you for your most informative reply.
                  You are welcome

                  Originally posted by BlueBell View Post
                  Rolls it is, 100 ah, MPPT and two panels.
                  I can add a third panel if sea-trials indicate it necessary... or can I, aren't the panels wired in series for a PMMT?
                  Yes and No. You want to run panel voltage as high as possible when using MPPT which is a very good thing as it improves efficiency and keeps cost and weight down. Higher voltage = less current, smaller wire, and lighter weight. However controllers have Voc limits and the number of panels you use determine what you can do. SO THINK THIS OUT

                  Example if you use a prime number of panels only gives you 2 panel configuration of all in series or all in parallel. So if the controller you buy is say has a Voc limit of 4o volt with 3 panels you are screwed and be forced to wire all the panels in parallel. That means 3 times the current and much larger wire is required, combiners, fuses, etc to do that. That is a lot of wasted money and added weight. So when you look at Controlers you want the Voc to be 100 volts or higher so you can at least wire 3 panels in series. Other than 1 or 3 do not use a prime number of panels.

                  Last thing if you plan to expand requires you to buy a controller that will allow that. Example if you bought a 15 amp model is maxed out at 200 watts with a 12 volt battery and 400 watts with a 24 volt battery. Real simple to figure out with a simple formula.

                  Charge Amps = Panel Wattage / Nominal Battery Voltage.

                  Example 300 watts / 12 volts = 25 amps

                  One more caveat and not many options. Controllers and salt water/air do not play well together. Very few Marine options on the market.





                  MSEE, PE

                  Comment


                  • #10
                    Sunking, thanks again for your interest and input.

                    I found a MorningStar marinized, 15 amp MPPT but it's Voc is 60 and my panels are 21.6 Voc each times 3 = 64.3 Voc... so that won't work.
                    Besides, 300 watt divided by 12 volt is 25 amps... so it definitely won't work.
                    But it would work for two panels... or would it at 16.7 amps? (see edit below)

                    Too bad I can't simply run the panels, in series, directly to the battery through a manual switch, as overcharging doesn't sound like it's going to be an issue.
                    But the voltage would be too high for my components...
                    Is there any way to make this idea work with a voltage limiter between the battery and load?

                    Edit: Just realized this on the spec sheet
                    ​​​​​​*Input power can exceed Nominal Maximum Operating Power, but controller will limit and provide its rated continuous maximum output current into batteries. This will not harm the controller (reminder: do not exceed Voc).
                    Last edited by BlueBell; 03-15-2018, 01:26 PM.

                    Comment


                    • #11
                      or you could try the Midnight Solar Kid Marine which is 30a capable and 150V input

                      http://www.midnitesolar.com/productP...tOrder=2&act=p
                      OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

                      Comment


                      • #12
                        Originally posted by ButchDeal View Post
                        or you could try the Midnight Solar Kid Marine which is 30a capable and 150V input

                        http://www.midnitesolar.com/productP...tOrder=2&act=p
                        Took the words right out of my mouth

                        THX
                        MSEE, PE

                        Comment


                        • #13
                          Originally posted by BlueBell View Post
                          Too bad I can't simply run the panels, in series, directly to the battery through a manual switch, as overcharging doesn't sound like it's going to be an issue.
                          But the voltage would be too high for my components...
                          Is there any way to make this idea work with a voltage limiter between the battery and load?.
                          Technically you can bu there is the problem and why PWM controllers suk.

                          The panel current is roughly 5.3 amps right? Wire three panels in series and you still have 5.3 amps charging into a 12 volt battery. 5.3 volts x 12 volts = 64 watts from 300 watts of panels

                          Wire them in parallel and you have 5.3 amps x 3 panels x 12 volt = 190 watts from 300 watt panels.

                          MPPT = 300 watts / 12 volts = 25 amps.

                          You can use the controller you found, you would just have to wire 3 panels in parallel series which suks. Cough up the extra cash and get the Midnite Solar Kid Marine unit. Or just settel wiht 200 watts of panels. You really do not want much more than 200 watts into a 100 AH battery. For 300 watts you would really need a 150 AH battery. Do not push charge current much past C/4 on an AGM.
                          Last edited by Sunking; 03-15-2018, 03:02 PM.
                          MSEE, PE

                          Comment


                          • #14
                            Okay, thank you, all.
                            What an education.

                            I realized today, while waiting for my daughter at school in the 650 watt per square meter sunshine,
                            there may be down times during the race when electrics are off, zero draw.
                            Weather, tides, and fatigue can cause stopages, especially if I'm ahead and can afford the time.
                            ( I may even have shore power. I have a good, small, 20 amp, 120v marine charger. )

                            It makes sense to me then to go with two panels, the 15-amp MPPT and a 100 or 120 ah AGM.

                            The MidNite30 is more than 5X the weight, 18X the volume and double the price of the MorningStar15.
                            Space in the cockpit really is an issue.
                            It's a nice unit but hard to justify.

                            And just to be clear, the panels would be in series, right?
                            Last edited by BlueBell; 03-15-2018, 08:45 PM. Reason: Clarity

                            Comment


                            • #15
                              Originally posted by BlueBell View Post
                              And just to be clear, the panels would be in series, right?
                              Correct assuming no shade issues.

                              MSEE, PE

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