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Old 10-15-2017, 08:07 AM   #1
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2017 22' Sport
NCR , Ontario
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solar panel: series or parallel

if you install 2 or solar panel, which option is recommended and why

Benefit of Series Wiring
Panels are combined and create higher voltage. Because of the higher voltage, the wires to the charge controller can be a smaller gauge (thinner) and the run can be longer. This is great for going through walls and tight spaces.

Benefit of Parallel Wiring
Each panel works independently. If one panel is shaded, it will not affect the entire solar array. This is great for an RV in the woods with varying shadows throughout the day.

here is the wynn's testing both options
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Old 10-15-2017, 08:37 AM   #2
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We did series wiring on two Sharp 125w panels. Nominal 24vdc is recommended by our MPPT controller mfr and, as you mention, wire size is smaller for 1/2 current. It's worked well for us.
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Old 10-15-2017, 10:02 AM   #3
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1994 30' Excella
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I installed four monocrystalline flexible panels in series. Voltage runs around 64 volts. my charge controller can handle that. Works very well for me and I used 11 guage wire with mp3 connectors. The new connectors now are mp4.
Also these panels are less efficient than the polycrystalline ones but are not badly affected by partial shading or heat.
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Old 10-15-2017, 10:46 AM   #4
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The effect of shading in series operation can be mostly mitigated (at least to be roughly equivalent to parallel connection) by the use of bypass diodes for each solar panel. Some commercial junction boxes may have these diodes already. If the user simply hooks up bare panels in series without a bypass diode for each panel, when a panel is shaded it will block current from the other panel from reaching the charge controller. Here is an article on the selection of bypass diodes to be added to junction boxes.


Panels already have the individual cell group bypass diodes, but in the event of significant panel shading, the internal bypass diodes are placed in series, multiplying their forward voltage drops and increasing loss. A single bypass diode around the entire panel allows most of the power (all of the current at a voltage reduced by one diode forward voltage drop) to get to the controller.

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Old 10-21-2017, 03:55 PM   #5
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I did extensive research on this as I am in the midst of installing a 200W setup on my AS.

The answer is it somewhat depends as there is a convolution of factors, and as always, it's dependent on variables for your specific setup. Though things seem to favor PARALLEL more often than serial for MPPT controllers (PWM can only do parallel). Which is supported by professions from Lewster to AMSolar whom recommend parallel wiring

One of the common reasons for serial I've read on the boards is wiring gauge. True, higher voltage increases transmission efficiency over smaller gauge wire. But rarely talked about is this:
1) The greater discrepancy between array and battery voltage, the bigger reduction of the conversion efficiency of the controller.
2) MPPT controller efficiency tends to drop way off at lower currents, which is another strong reason to wire in parallel.

Here's my particular controller, but you can see the general efficiency trends:
Click image for larger version

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For 200W, wiring absolutely should be parallel.

For 400W, if on really wants to use the 10gauge pre-wire, I can see potentially a series/parallel wiring of the panels to balance the tradeoffs. Optimally, it should be all parallel with upgraded wiring.
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