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Old 02-03-2019, 09:58   #1
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Adding Solar capacity in Parallel

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I am considering adding a 5th Solar panel over the tender davits to complement the 4 x E-Series Sunpower 327w panels.
Sunpower is no longer available in the Philippines so I am looking at other makes of same Wattage size but electrically the Specs are different from Sunpower.

In parallel, is that an issue as I am using the one Outback 80, which has enough capacity to handle the 5th panel?
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Old 03-03-2019, 03:20   #2
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Re: Adding Solar capacity in Parallel

Best to add a dedicated SC for the non-matching panel.

Victron 75/15 or similar is not expensive.
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Old 03-03-2019, 03:45   #3
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Re: Adding Solar capacity in Parallel

Thanks John . I thought about going that direction, the only downside is that I was going to combine all panel cables near the stern and run 2 to the Outback as it is a long run
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Old 03-03-2019, 04:38   #4
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Re: Adding Solar capacity in Parallel

Maintaining top efficiency, maximizing output

vs convenience, lower cost

Up to you
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Old 03-03-2019, 05:04   #5
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Re: Adding Solar capacity in Parallel

Just add it. The controller will find the best power point. Maybe you don’t get as much out of the new panel as you could, but that’s on paper.
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Old 03-03-2019, 05:38   #6
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Re: Adding Solar capacity in Parallel

The increased MPPT hunting may well reduce the overall output from the existing panels.

But sure, long as you do proper A/B testing, try it and see for yourself, no harm done.
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Old 03-03-2019, 07:19   #7
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Re: Adding Solar capacity in Parallel

Is it a 12v or24v system? If it is a 12v system you could already be over capacity for the fm80. These units log data for 180 days. What has been your maximum output in amps?
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Old 03-03-2019, 09:56   #8
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Re: Adding Solar capacity in Parallel

I'd also put a Shotkey diode in that power lead from ea panel....then each can act as its own w/o backfeed from any of the others. Our system has 4 panels; each panel power lead (+) goes to a Shotkey diode, then to a common busbar, and a single feed from that busbar to the Victron controller, and to the house battery bank. Adding another panel to that common busbar should not be an issue if the controller can handle it.
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Old 03-03-2019, 10:58   #9
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Re: Adding Solar capacity in Parallel

Aurinco (sadly, no longer in business) maintained that adding a series Schottky diode was not necessary. They said you lost more energy in the diode during daytime charging than you would lose overnight due to back feed.
Further, the MPPT controller already eliminates back feed.
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Old 03-03-2019, 11:52   #10
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Re: Adding Solar capacity in Parallel

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Originally Posted by senormechanico View Post
Aurinco (sadly, no longer in business) maintained that adding a series Schottky diode was not necessary. They said you lost more energy in the diode during daytime charging than you would lose overnight due to back feed.
Further, the MPPT controller already eliminates back feed.
Solar controller prevents battery from leaking current back into panels when they all are shaded. But for panels in parallel,
no controller can eliminate reverse leakage of one shaded panel connected in parallel with another panel which is in sunlight and producing power. On other hand, reverse diode leakage of an undamaged solar panel should be negligible.
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Old 03-03-2019, 12:28   #11
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Re: Adding Solar capacity in Parallel

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Solar controller prevents battery from leaking current back into panels when they all are shaded. But for panels in parallel,
no controller can eliminate reverse leakage of one shaded panel connected in parallel with another panel which is in sunlight and producing power. On other hand, reverse diode leakage of an undamaged solar panel should be negligible.
Yes. There was a discussion here about the reverse diode, and one valid reason was to protect against catastrophic damage (including fire) should a paralled panel cell fail in a particular way. Otherwise, more loss than gain.
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Old 03-03-2019, 14:50   #12
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Re: Adding Solar capacity in Parallel

As long as the output unregulated voltage from the panel matches that of the other panels, and the amps delivered is about the same--there will be no problems with your existing regulator if it does have the capability of handling the combined current output/draw.

Having said that, I have no more than two 100 watt panels on each of two regulators, and those regulators are wired in parallel. If I needed extra panels, I would add the extra regulators, and match the output regulated charging volts of each to the others. That way if I have a faulty regulator at any stage, I am not without power.

Mine are adjustable. They do not need to be absolutely identical in volts output, but they need to be as closely matched as you can make them.
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Old 03-03-2019, 15:39   #13
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Re: Adding Solar capacity in Parallel

Thanks All, much better picture of the issues now.

My House Bank is 24v and the most I have seen delivered at 28.8V is 42amps, which delights me!
The Outback is rated 80amps maxumum Output, so I think I'm ok with one more 96 cell panel connected around 330w
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I am at a friend's shipyard right now so welding the supports over the Davits is easy, but the challenge is finding another make panel that matches close to Sunpower.
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John suggested testing before buying a sperate SC which makes sense .

The one part that confuses me is whether I need blocking Diodes as there are different opinions.

At anchor I really don't get much shade
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Underway, I would usually be motor sailing at 1000rpm making water and charging batteries with the large case Alternator.

The 5th panel at davits should have little or no shading
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Old 03-03-2019, 16:01   #14
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Re: Adding Solar capacity in Parallel

Most MMPT controllers are capable of hi input voltage . They then convert it to proper output for your charging needs .
For that reason and since you have a long run I would suggest you put the panel in series .
It will up your input voltage and in turn keep the amperage lower which both benifit a longer run .
An added benifit by running in series is your controller receives a usable voltage in low light conditions.
I have my boat this way and total daily output is higher due the extra couple hours I get every day .
I'm here in the Philippines also . In Puerto.
Where are you located ?
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Old 03-03-2019, 16:18   #15
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Re: Adding Solar capacity in Parallel

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Just add it. The controller will find the best power point. Maybe you donít get as much out of the new panel as you could, but thatís on paper.
Btw- instead of asking a forum I asked the same basic question to Outback because I also had a panel that could be exactly matched. They said it was ok and the controller would just find the max power output from the panels
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