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Old 18-05-2007, 12:04   #1
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Wiring Solar panels

My boat is almost ready to hit the water after the new coat of paint and repairs. The batteries have now been replaced and I am ready to wire up the 4 130 watt panels.
Does anyone have an idea as to how to do this correctly. There is a solar regulator in the boat with a red and a plack pole, however I am not sure if the panels are wired negative to negative, or pos to pos
Thanks
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Old 18-05-2007, 12:13   #2
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The first thing I'd do, is check the panel manufactures website. They generally have pretty good monthing and wiring instructions. I then look up the solar controllers specifications to see what type of flexibility I had there. Generally, you're going to be wiring + to + and - to - (parellel). BUT, depending on the controller/regulator, you may have other options (series).
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Old 18-05-2007, 12:49   #3
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I wired my KC130's in series, not parallel (That is pos to neg). I have a Outback MX60 MPPT charge controller, and series is their suggestion. If you do not have a MPPT charge controller, you will not get the most out of your solars and will be very dissapointed. Go call N Arizona Wind and get an Outback MX-60. Probably the best on the market for a large array.

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Old 18-05-2007, 19:18   #4
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I too would suggest going to the panel manufacturer and the controller Manufacturer for the correct connections and wiring.
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Old 18-05-2007, 19:27   #5
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"There is a solar regulator in the boat with a red and a plack pole,"
If those are the only inputs it has, odds are it is an old-fashioned regulator and they take the panels all wired in parallel, all the reds to one point, all the blacks to the other point. But you can't assume with this stuff--you need to verify it with the regulator maker.
A new MPPT type (Outback or Blue Sky) could give you 30% more power from your panels, but might easily cost $400+.
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Old 18-05-2007, 22:28   #6
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How much voltage does each panel put out? If it is under 13 volts per panel the panels will have to be wired in series to provide aiding supplies so it can then be regulated back down to 13.8 approx. which is the charging voltage you need to charge your batteries .
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Old 17-10-2008, 07:36   #7
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series or parallel?

I'm hooking up two 130W panels through a blue sky mppt controller. I can hook them up either in series or parallel. Which is better? They are 17v panels.

If I hook them in series I get less loss through the wiring because of higher voltage, or I can use smaller wiring. However, I have read that with a series installation shading on one panel will limit the output of both, is that true?

I see that Cruising dad went with series installation, is that the norm?
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Old 17-10-2008, 08:35   #8
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True both ways. I believe the situation is something like casino gambling: No matter how you play, you lose. So, toss a coin, play a hunch. With a series hookup I think BS claims another 2% gain in conversion efficiency. Shadowing will only be an issue if you point the boat the wrong way, and let a shadow fall on the panels.<G>
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Old 18-10-2008, 01:20   #9
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The voltage supply level and current charging capability is not fixed in a solar panel. If you have constant 17 v output because you get maximum solar input living in a very sunny place you would get the best recovery by hooking them up in parallel, not losing as much in a 12v charging regulation. If you live in the PNW as I do when I am there with less than optimum solar recouvery. Clouds and rain take thier toll. You would hook them up in series to get maximum usage of your panels. If your panels are only putting out 9 volts each because it is a cloudy day you will still get some charging if the are in series. The total 18 volts can be regulated down by the controller to 13.8 - 14.4 volts however if they were connected in parallel the total output voltage would be 9 volts, not high enough to be considered as a supply for charging. A good controller would be able to do the switching between series and parallel to maximize the efficiency or have a wide range dc to dc converter to improve the performance of either.
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Old 18-10-2008, 10:38   #10
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The voltage output from the panels (9 vs 17 vs 14) won't matter with an MPPT controller. There's no dumping and waste from overvoltage, no undercharging from undervoltage or parallel panles. The MPPT controller will convert whatever power there is (power, not amps or volts but watts) into whatever can best charge the battery at whatever state it is in.
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Old 20-10-2008, 08:28   #11
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Hellosailor is correct, the MPPT will autocorrect. I would do a few things first, make sure the MPPT is not by the battery bank as it's not ignition protected so it could potentially ignite off gas from the batteries. I would also make sure you have a good high amp breaker installed prior to the battery bank. For 4 solar panels I've hooked mine up to a junction box and then wired them in parallel as they are around 36 volts coming directly out of the panels themselves. You've got panels with half the voltage of mine, so if you think you could get shadow over one side of the array, you could hook them up in series on a given side (port together in series and starboard together in series), and then bring them together to a junction box and hook them in parallel going forward to your charge controller. That way you get the best of both worlds, higher voltage and less transmission loss, plus the ability to not have you entire array go down because of shading of a single panel. The biggest mistake I've seen is under sizing the wires coming from the panels to the charger. When you plug in the best practices you should have a system capable of handling 156% more power than you could produce at maximum. Look at this link at the bottom Solar power - voltage drop tables for your solar power project.
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Old 21-10-2008, 05:57   #12
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Originally Posted by schoonerdog View Post
The biggest mistake I've seen is under sizing the wires coming from the panels to the charger. When you plug in the best practices you should have a system capable of handling 156% more power than you could produce at maximum. Look at this link at the bottom Solar power - voltage drop tables for your solar power project.
The size of the wire is one of the things that has surprised me. I hadn't been expecting to run a pair of #6 wire through my deck, your chart showed me needing something between #4 and #6 (a 3% voltage drop would allow me to use #6).

Apparently Blue Sky didn't think about this either(or didn't care), because the terminals on the mppt are sized to handle the little miniature ring terminals that aren't as wide as the #6 wire. So after running 20 feet of nice heavy wire through my deck and boat I have to add another weak link and splice in a foot of #12 wire going in and out of the MPPT. Any better wiring solutions than this?
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Old 21-10-2008, 09:12   #13
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Apparently Blue Sky didn't think about this either(or didn't care), because the terminals on the mppt are sized to handle the little miniature ring terminals that aren't as wide as the #6 wire. So after running 20 feet of nice heavy wire through my deck and boat I have to add another weak link and splice in a foot of #12 wire going in and out of the MPPT. Any better wiring solutions than this?
I also was disappointed at the terminal size on the Blue Sky MPPT controller, and I did have to splice in a short #12 service loop to make the connection. The good news is that the length of #12 is so short that the voltage drop is inconsequential, and the #12 is well-within it's safe current-carrying capacity. So, other than the nuisance factor, it's not a big deal.
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Old 21-10-2008, 12:09   #14
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The voltage supply level and current charging capability is not fixed in a solar panel. If you have constant 17 v output because you get maximum solar input living in a very sunny place you would get the best recovery by hooking them up in parallel, not losing as much in a 12v charging regulation. If you live in the PNW as I do when I am there with less than optimum solar recouvery. Clouds and rain take thier toll. You would hook them up in series to get maximum usage of your panels. If your panels are only putting out 9 volts each because it is a cloudy day you will still get some charging if the are in series. The total 18 volts can be regulated down by the controller to 13.8 - 14.4 volts however if they were connected in parallel the total output voltage would be 9 volts, not high enough to be considered as a supply for charging. A good controller would be able to do the switching between series and parallel to maximize the efficiency or have a wide range dc to dc converter to improve the performance of either.
I'm curious as I don't have solar panels yet, have you actually measured low voltages on cloudy days? I ask because looking at solar panel specs shows that voltage output is relatively unchanged by light intensity, it is the current output that drops.

The dotted lines on the graph on the web page below shows outputs at different light intensities. As you can see at the open circuit end of the graph, the voltage output is 20 volts at 1/5th the light of max light at which point it produces 22 volts.

As others have said, with an MPPT controller you can go either way, but I've convinced myself that with all the possibilities of shading a panel on a boat, I'm going with the panels in parallel route with big wires.

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Old 21-10-2008, 14:02   #15
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Running a foot of #12 would do, but whenever there's a heavy cable attached to a thinner wire, I worry about the cable working the wire and causing something to snap, unless the end of the cable is secured, i.e. strapped down to a bulkhead or something. At that point, you might as well just a junction block, affixed to the MPPT controller or to the hull next to it, so that the cables can be secured to the junction block, and the shorter lighter runs to the MPPT controller are entirely separate--and carrying no physical loads, just electrical ones. Also remember to install a drip loop in those final "jumpers", since most MPPT controllers wouldn't like condensate or leaking running down the wires into them.
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