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Thread: Solar question(s)

  1. #11
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    I am planning to install two 55 watt solar panels on the pushpit of my Express 27. There is an existing 5 watt panel on the back deck. All three will go to a 10 amp charge controller. What is the recommended wiring from the panels to the charge controller?

    I spoke with someone from Northern Arizona Wind and Solar who said that I should have each panel individually fused and switched (or circuit breaker) at a junction box followed by another fuse/switch (or circuit breaker) between the junction box and the charge controller.

    This sounds a little excessive. I can see the advantage of having each panel individually switchable, for troubleshooting and verifying function, but the maximal short circuit current of all three panels is only 6.9 amps. So why have a fuse?

    I do understand that a fuse is required close to the battery to protect the wiring, but I am thinking about not using a fuse between the panel and the charge controller. I would like to keep things as simple as possible, but it must be safe.

    Thank you,
    Todd
    Last edited by todd22123; 08-08-2013 at 07:04 PM.

  2. #12
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    Hi Todd,

    I have my two 43-watt panels wired together, then to one of these, and then out to the two Group 27 AGM's. No fuses other than the single fuse on the PV7D.

    You're pushing a bit more juice than I am, but I tend to agree with you that all that fusing is overkill. Others?

    http://www.flexcharge.com/PV7D.html
    Last edited by BobJ; 08-08-2013 at 07:05 PM.

  3. #13
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    See http://www.pbase.com/mainecruising/solar_panel&page=1 for excellent install instructions.

    I have two separate Genasun GV4 controllers wired to two panels (Bruce Schwab and Genasun's recommendation) on my Moore. Genasun's installation instructions doesn't mention fuses between panel and controller, and I don't have one in line. I'd call them, as the Genusun folks are very helpful, and fed ex'ed a replacemet overnight.

    All that said, here is the wiring section from Maine Cruising:

    "Wire The Controller
    A solar panel sized to actually "re-charge" a bank, not just maintain it, should ideally be routed directly to the house bank. The white jacketed wire coming into this Genasun controller is the panel feed. The connections are easy and clearly labeled on most controllers. Hooking them up is the easy part.

    The black & red wires leaving the controller go to the house bank. The red wire is "switched" so the panel can be turned off if needed. Check with your controller manufacturer to see where an ON/OFF switch can be installed if you want the ability to flip the panel OFF. ON/OFF switches are normally installed on the battery/output side of a controller but this can vary from manufacturer to manufacturer.

    There is also a fuse in the red wire between the battery bank and switch, that can't be seen. It is installed close to the battery + post. When connecting anything directly to a battery bank the wire should be fused. The ABYC suggestion is for the fuse to be within 7" of the + post of the house bank. While not always possible to be within 7" try to get it as close as possible.


    If you have a secondary starting or reserve bank you can then use a device like an Echo Charger or an VSR type relay to charge the start or reserve bank and keep it topped up. Even without a solar panel an Echo Charger or VSR are useful devices.

    Some charge controllers, such as the Morningstar SunSaver Duo PWM, can charge two banks simultaneously. This is a nice feature if you don't have an Echo Charger or VSR to charge two banks from one array."

  4. #14
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    Quote Originally Posted by todd22123 View Post
    I am planning to install two 55 watt solar panels on the pushpit of my Express 27. There is an existing 5 watt panel on the back deck. All three will go to a 10 amp charge controller. What is the recommended wiring from the panels to the charge controller?

    I spoke with someone from Northern Arizona Wind and Solar who said that I should have each panel individually fused and switched (or circuit breaker) at a junction box followed by another fuse/switch (or circuit breaker) between the junction box and the charge controller.

    This sounds a little excessive. I can see the advantage of having each panel individually switchable, for troubleshooting and verifying function, but the maximal short circuit current of all three panels is only 6.9 amps. So why have a fuse?

    I do understand that a fuse is required close to the battery to protect the wiring, but I am thinking about not using a fuse between the panel and the charge controller. I would like to keep things as simple as possible, but it must be safe.

    Thank you,
    Todd
    Tie all three panels in parallel, red to red, black to black, and attach to the charge controller input. A panel failure, say a crack or short, will not impact the other panels as the panels contain a diode that prevents reverse currents from flowing. Also preventing the tiny bit of loss that can occur when a panel is darkened. One fuse on the battery side is sufficient.

    If you are charging multiple banks, and it sounds like you are not, you can use a set of switches to select the battery to be charged. If your batteries are in parallel there is no need for battery selection. More advanced controllers can switch between banks automatically.

    There is another controller type that will boost the voltage of panels that have fallen below 12 v, say the panel is in shade, using a boost switching technique. These improve efficiency of your panel output as they will recover a small fraction of energy as the panel voltage swings a bit with each swell passing under the boat.

    Some of the flex panels only output 8 volts peak and require a unique controller type that boosts the voltage for charging. This is a type of switching regulator. This is why you will see recommendations for multiple controllers in those cases. You can choose to series two of the 8 volt flex panels and arrive at the equivalent output voltage of the typical 17 volt peak seen in most panels for marine use. This then allows the flex panel to be used with an existing charge controller.

    There is also another type of controller that has much higher voltage input capability than the average simple controller. These are normally used in multi panel installs and the panels are connected in series generating up to hundreds of volts. THese controllers, like the ones used with flex panels, employ a switching regulator to bring down the voltage to the regulation point.

    On my Olson 34 I have a simple charge controller and several panels tied in parallel driving the same. On a recent long passage, at one point, I was not getting charge from the panels. The simple parallel connection of the panels allowed me to take the controller out of the circuit and drive the batteries barefoot while I sorted out the controllers problem.

    Bobj's controller looks like a good choice for small installations. There are several brands out there that use a similar internal circuit and provide the same functionality.

    Brian
    Last edited by brianb; 08-09-2013 at 05:34 PM.

  5. #15
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    Arizona Wind & Solar sells a lot of different stuff. The Kyocera panels you're talking about were originally designed for static installations. They're not sealed along the frame. Adam Correa used two of those on his Folkboat in the 2010 SHTP and saltwater got into the junction box and ruined the panel in 21 days. Some of you might have a little quicker trip than he did, though. LOL!

    My panels are rigid frame, polycrystalline panels and use small cell technology. 36 cells in my 50-watt panel. This really helps with partial shading or low incident of light situations such as extreme sun angle. The frame is sealed with polysulfide (not silicone), as is the junction box. I use a very expensive junction box that has a packing gland type entrance for the wires and a rubber o-ring gasket on the lid. They were designed from the outset for marine use. They're about 2' x 2' square and are an excellent value for a saltwater-rated panel. You can check them out on my site at www.southboundsolar.com.

  6. #16
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    I used a 130W Kyocera panel from Arizona Wind & Solar last summer without problems. But then, I did not have waves breaking over it, either. I think this panel was advertised in their site as 'popular for marine applications'.

    One thing I did do on a friend's recommendation is to wire from the panel, through a fat grommet/fitting/hole in the boat right through to the charge controller, without a connector. No connector, no connector failure. I have since modified this to a connector and now use a baby 10 W ruggedized panel just to trickle charge the battery when I am away, so I don't have to leave the boat plugged in to shore power. Some say this cuts down on galvanic corrosion in marinas that are 'hot' or have bad shore power grounding.

  7. #17
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    Quote Originally Posted by robtryon View Post
    Arizona Wind & Solar sells a lot of different stuff. The Kyocera panels you're talking about were originally designed for static installations. They're not sealed along the frame. Adam Correa used two of those on his Folkboat in the 2010 SHTP and saltwater got into the junction box and ruined the panel in 21 days. Some of you might have a little quicker trip than he did, though. LOL!

    My panels are rigid frame, polycrystalline panels and use small cell technology. 36 cells in my 50-watt panel. This really helps with partial shading or low incident of light situations such as extreme sun angle. The frame is sealed with polysulfide (not silicone), as is the junction box. I use a very expensive junction box that has a packing gland type entrance for the wires and a rubber o-ring gasket on the lid. They were designed from the outset for marine use. They're about 2' x 2' square and are an excellent value for a saltwater-rated panel. You can check them out on my site at www.southboundsolar.com.
    I don't see the junction boxes listed separately on your site, although they may already be in use as my setup (installed by Ruben Gabriel on Rushmoore) was from SBS.

  8. #18
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    The author of the link provided by SMBReno makes a fairly compelling case for MPPT controller over PWM.

    Todd

    Quoted from http://www.pbase.com/mainecruising/solar_panel&page=1

    "There are essentially three types of controllers;

    MPPT = Multi-Point Power Tracking - In a nut shell MPPT controllers take excess voltage and turn it into current rather than wasting it. Your batteries only need around 14.4V to charge but you have panels putting out roughly 18+V. Without an MPPT controller this excess voltage is just wasted and lost. An MPPT controller converts excess voltage, above the 14.4V or what ever you set it at, into usable charging current. The claims are 10 - 30% more output. I must admit I have never seen a 30% boost but I have seen 6-14% increases over the max panel amperage output.
    Most MPPT controllers will work best when your array gets over 150-180 watts in size. The Genasun MPPT controllers are specifically engineered for small panels below 150W and are the only MPPT controllers I know of specifically designed as such. They extract the max current they can out of small panels and they work quite well.

    PWM = Pulse Width Modulated - These are the best alternative to an MPPT and they charge quite efficiently but can not turn excess voltage into current.

    Shunting Controllers - These controllers shunt or switch the panel current/voltage OFF when a preset voltage is reached and then turn back on when the battery bank voltage drops/falls to a second preset ON voltage. These are the least desirable controllers. If a controller does not specifically say PWM or MPPT is is probably a cheap shunting controller. I can not suggest spending your hard earned money on shunting controllers for a marine solar application. (SEE VIDEOS BELOW FOR ACTUAL BEHAVIOR) "

  9. #19
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    Todd,

    I have a 300 watt array on my vessel, and I see an honest 30% output gain over the PWM controller I previously used. The array's maximum power voltage (Vpm) is 18 volts. That gain diminishes slightly as the battery bank terminal voltage reaches 14.4 volts since the "delta" between the array voltage and the battery voltage is smaller as the batteries reach full charge. I have my system carefully instrumented and I am very pleased with the improvement over the old PWM controller.

    One thing to watch out for however is RF interference (RFI) produced by MPPT controllers. MPPT controllers internally use a switching-mode (square wave) DC-to-DC converter which can produce a lot of harmonic hash on your SSB receiver. You can detect the RFI as noise equally spaced across the entire HF band, sounding like what we hams call "birdies." I cured that problem with snap on ferrite suppressors - a cheap and simple solution. You can buy them either at a local Ham Radio Outlet or on line from DX Enginnering. When installing the ferrites, be sure to snap them over BOTH the positive and negative leads TOGETHER so that the algebraic sum of the DC currents passing through the ferrite is zero. Otherwise, if the DC currents passing through the ferrites aren't in exact opposition, the DC current will saturate the ferrite core and you will lose all RFI suppression. They'll behave as if they weren't there at all.

    Place the ferrites as close as possible to where the wires exit the MPPT controller case. I personally chose the Blue Sky controller because it is installed in a metal housing, which provides additional RF shielding.

    73, N8QH
    Last edited by pbryant; 08-19-2013 at 06:41 PM.

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