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    Solar Battery Chargers-gctid365244

    We don't have shore power available where I have my 1989 Ciera 2556 (Homer, AK). Some of the births have it but not all and not mine. I am thinking about getting a solar panel from Home Depot to try to keep the batteries tip-top. It's a Sunforce 15 amp, panel for charging 12 volt batteries. Comes with a controller so it can't overcharge the batteries. Costs $115.00. We get lots of sunlight here in summer and I think it would be good. It says you have to disconnect the panel before start up. Otherwise, I think it might relieve the worry about dead batteries due to disconnect from the shore power. Wondering if anybody has had experience with this. West Marine in Anchorage has a 80 watt one for $576.00 and a bigger one for more $$$. I just want to make sure there is power to keep the bilge pumps running if needed, and also to make sure I start up every time.

    #2
    Good thought. I'm no expert, but I've heard that those little ones are next to useless. A 15 amp however should be enough to keep one battery up to charge. Problem is I don't think you can charge both

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      #3
      The Sunforce from HD is a 15 watt, not 15 amp. It puts out around 1 amp at full power. Maybe enough to trickle charge one battery, but that is about it.

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        #4
        I had a rather huge solar panel on a previous boat which was kept in dry storage. The size was around 15x30 and it was rated at just over 1 amp. In the AZ sun in summer, it still couldn't keep up with just floating the batteries and the parasitic loads from little things like the radio memory, CO detector, etc. It was useful only if I made sure to disconnect absolutely everything. In that case sure, it will keep the battery topped up, but you only need that if the boat sits unused for months at a time.

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          #5
          ouch, I had no idea they were of so little use :thumb

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            #6
            LazyCrusr wrote:
            ouch, I had no idea they were of so little use :thumb
            I've been looking into solar panels for a few years now and watching as the pricing is slowly going down.

            You need to know the amperage that the panel is capable of suppling. The wattage means very little as amperage is constant and ohms law does not apply to solar panels. I've seen 80 watt panels that can supply 5 amps and 175 watt panels that only can supply 5 amps.

            To maintain a good charge you need a good controller and about a 5 amp panel as it only gives out 5 amps at max sun light.

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              #7
              I am so glad I live in Seattle - due to the fact there is never any sunlight when the boat is sitting on the trailer, not only do I never have to worry about how many amps, watts, etc etc are required, but as a bonus, I will never have to budget any money for buying solar panels!!

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                #8
                The wattage means very little as amperage is constant and ohms law does not apply to solar panels.
                That's not true. Watts is EVERYTHING when it comes to any electrical measure. Watts is the measure of actual work and energy. Amps combine with voltage to make watts. If a device needs 100 watts, and it is getting 12 volts, it's using 8.33 amps. When the battery starts to get low it will still use 100 watts, but if the battery is at 11 volts it will draw 9.09 amps.

                A solar panel may put out 100 watts by producing 14v and 7.14a, or it may make 100 watts by producing 18v 5.55a. The constant is always the watts.

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                  #9
                  Boat and RV people I've talked to were disapointed with the performance of their solar. If you were able to install large enough pannels it could help maintain a boat on a mooring or a stored RV but not enough to be helpfull for usefull purposes. One fellow said a couple hours on a 2K Honda generator will cover the loss better than his pannels.

                  I'm sure they have their place but most users who don't realisticly calculate the Amp/hours expect too much from them. We have to put back what we take from the batteries it's not rocket science. Sometimes I think the manufaturers want it to be confusing by changing the terminoligy (watts, amps, millamps, amp/hours) and exaggerating their performance so they can sell under rated products then sell bigger ones later.
                  Carl
                  2452

                  Comment


                    #10
                    BLCarl wrote:
                    Boat and RV people I've talked to were disapointed with the performance of their solar. If you were able to install large enough pannels it could help maintain a boat on a mooring or a stored RV but not enough to be helpfull for usefull purposes. One fellow said a couple hours on a 2K Honda generator will cover the loss better than his pannels.

                    I'm sure they have their place but most users who don't realisticly calculate the Amp/hours expect too much from them. We have to put back what we take from the batteries it's not rocket science. Sometimes I think the manufaturers want it to be confusing by changing the terminoligy (watts, amps, millamps, amp/hours) and exaggerating their performance so they can sell under rated products then sell bigger ones later.
                    I ordered one with 1.25 amp output, 15 watts total. It comes with a controller. The reviews were 53 out of 53 "would recommend it to a friend." Here are 2 of the reviews I think are relevant here. One is from a professional, the other from a marine user::

                    "This unit works great at our cabin up north. We have no electricity there so we use four 12 volt batteries in a series for the lighting, radio, etc. This unit keeps the batteries charged without over charging them and will de-sulfate the batteries as needed. Excellent product, highly recommended."

                    What is your level of technical expertise? Professional

                    "This is a most excellent product, it is easy to use and easy to set up and requires no maintenance....just plug it in, point it at the sun and it charges your battery while you do other things, great product for boaters too...I use mine to charge my house battery on my vessel...no more worring about a dead battery..even works on cloudy days"

                    What is your level of technical expertise? Home Handyman

                    Comment


                      #11
                      Yes, those reviews say that the product is "functional." However, what is your expectation of the result? If you're using more power than it can deliver, you're still going to be disappointed. Its rated output is still extremely tiny, and useful really only for a float charge and minimal vampire loads, nothing more.

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                        #12
                        If you get the good Z-grade 4" square cells and build your own panels, they can put out quite a bit more power. Alot of these panels are made with lower quality cells and poor encapsulation materials and techniques which don't put out alot of power.

                        I was part of a team in school that built remote control scale solar cars for a series of competitions, and learned alot about them.

                        For low light conditions, you can still pull decent power by wiring the cells in parallel. Like a battery the cells have internal resistance and wiring too many in series will actually limit performance due to the amp draw that can be passed thru each one. Our car ended up being about 30" long and about as fast as a kids toy radio shack car...maybe fast walking pace.. and would climb a 20* grade.....but even in overcast conditions it worked well and could be driven until you got bored with it.

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                          #13
                          SwampNut wrote:
                          That's not true. Watts is EVERYTHING when it comes to any electrical measure. Watts is the measure of actual work and energy. Amps combine with voltage to make watts. If a device needs 100 watts, and it is getting 12 volts, it's using 8.33 amps. When the battery starts to get low it will still use 100 watts, but if the battery is at 11 volts it will draw 9.09 amps.

                          A solar panel may put out 100 watts by producing 14v and 7.14a, or it may make 100 watts by producing 18v 5.55a. The constant is always the watts.
                          You really need to study up on solar panels before you post.

                          Comment


                            #14
                            You really need to study up on solar panels before you post.
                            I did.

                            But solar panels, or generator, or whatever, Watts is the measure of work. Always has been.

                            Comment


                              #15
                              SwampNut wrote:
                              I did.

                              But solar panels, or generator, or whatever, Watts is the measure of work. Always has been.
                              This is not the best explanation but you will get the idea.

                              http://www.windsun.com/ChargeControls/MPPT.htm

                              Using an MPPT controller helps but the current output of the cell is more or less fixed and the watts are implied.

                              So in answer to your a watt is a watt....only when it isn't!

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