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Old 03-03-2019, 20:43   #16
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Re: Adding Solar capacity in Parallel

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Originally Posted by wally m View Post
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 ?
There has been a lot of disagreement over Series/parallel wiring when it comes to Shading issues. General opinion being that parallel is better especially if you have high voltage panels as I have.

I'm in Subic, but PG is also a home.
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Old 03-03-2019, 20:48   #17
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Re: Adding Solar capacity in Parallel

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Originally Posted by sailorboy1 View Post
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
Devil is in the details??

Have now Sunpower with 22.5% cell efficiency x 4

What I can find locally in a single mono panel is around 17-18% efficiency

Would the Outback/Sunpower output be severely derated if it adding a less efficient panel?
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Old 03-03-2019, 21:54   #18
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Re: Adding Solar capacity in Parallel

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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.
Did you mean SunPower panels, or panels with SunPower cells are no longer available?
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Old 03-03-2019, 22:00   #19
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Re: Adding Solar capacity in Parallel

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Originally Posted by waterman46 View Post


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.
Actually the panels themselves eliminate backfeed. Each cell is basically a pn junction (diode). The only difference is the diode (cell) is forward biased (current flow) only when there is light on it, and reversed biased (no current flow) when there is no light on it.

Some panels may have a bypass diode, so that if a panel in a series string is shaded, and a cell becomes reversed biased, the current produced by other panels can bypass that panel, else the output of all panels in series would be limited by the amount of current passed through the reverse biased shaded panel.

When using panels of this size, connected in parallel, I recommend fusing each panel positive lead, so that if a panel develops a short circuit, the fuse will open so the other panels cannot feed the short circuit, and start heating things up.

I don't bother with fuses for parallel arrays of 4 x 100W or less, as the risk of generating enough heat to start a fire if a panel shorts is relatively low.

The fuses aren't required if connecting arrays in series, but series connection may not be desirable due to the shading problem if bypass diodes are not used.
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Old 04-03-2019, 02:45   #20
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Re: Adding Solar capacity in Parallel

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Originally Posted by fivecapes View Post
Did you mean SunPower panels, or panels with SunPower cells are no longer available?
SunPower had a large factory in the Philippines closed in 2016 and a new one opened in Mexico
I was able to buy my 4 panels from a small distributer near the Factory for 30% less than in the USA
Cost of shipping one panel from States or Mexico does not make financial sense
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Old 04-03-2019, 07:47   #21
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Re: Adding Solar capacity in Parallel

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Devil is in the details??

Have now Sunpower with 22.5% cell efficiency x 4

What I can find locally in a single mono panel is around 17-18% efficiency

Would the Outback/Sunpower output be severely derated if it adding a less efficient panel?
Define severely.

If you really want to add a panel, go for it and A/B test just adding it.

If the reduced efficiency is "too much" for **you** compared to the cost of a SC for just the added panel, then upgrade in order to increase your output.

No rush, n harm done in the meantime, as long as you don't exceed your existing SC input ratings.
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