Community Forums

dckromm · 07-14-2019, 08:51 PM

Does it really matter how you configure your solar panels, as long as you stay within the limits? Which is better, 4 in parallel or 4 in series?

Isaac-1 · 07-15-2019, 12:41 AM

4 in series is almost always going to be better than 4 in parallel assuming you have bypass diodes or no shading.

Sbrownstein · 07-15-2019, 02:23 AM

As long as you give the controller something to work with, that is voltage over maybe 18 volts it doesn't matter. Parallel means bigger wiring, series means be careful of shading the panels.

twinboat · 07-15-2019, 03:50 AM

In early morning or late afternoon lighting, if in parallel, each panel has to make at least 13 volts to give you any charge.

In series, each panel only needs to make 3.5 volts. This is where the MPPT controller can help.

dckromm · 07-15-2019, 05:36 AM

Thanks, you led me right into my next questions. I originally had then in parallel, but after computing the wire size needs and looking at the wires i had, changed them to series.
After that, the system seemed great. At 9AM I was at 100%, that was my first trip after the change. I was surprised because where I am is at the top of a mountain, with nearly no overhead sun.
The next trip was horrible. Now trip number one was in March with bare trees, while trip number two was in June with full foliage. Of course, every leaf seemed to be purposely positioned to create a problem.
It is sitting in a temporary spot, while I clear the driveway to the top where there is enough clearing to resolve the issue.
Any suggestions. Should I get a larger cable and go back to parallel. Which would create a wire too large for the controller issue? Should I make seasonal changes? Or would maybe sets of 2 in series than paralleled?

MeSteve · 07-15-2019, 07:53 AM

The 2 series, 2 parallel is a common solution to your shading issue. That way shade on one side won't hinder some generation in a sunny area on the other side of the rig.

John Hilley · 07-15-2019, 10:25 AM

If the cable is too large for the controller terminal, you can terminate it on a Power Post and then use largest cable that controller can terminate as a short jumper between power post and controller.

dckromm · 07-15-2019, 10:58 AM

Thanks for the great suggestions. I will, on my next trip try out and test series parallel connections, with 2 pairs of 3 and 3 pairs of 2.
I also ordered some connectors. I have Oxygen Free Cable in several sizes. I will first try to make new cables using 8 gauge. It is 805 strands and rated at a much lower loss. Even if I use 10 gauge it should be an improvement.

leadman · 08-30-2019, 03:54 PM

I have seven 100 watt panels that have individual wires running down to an ATC fuse box next to the controller that combined the input from each panel to one terminal that goes to the controller. The grounds all go to a large power post then to the controller.
Has been working great for a couple of years now. Started out with 4 panels and been adding on.
The individual wires make it easy to test individual panel output without getting on the roof. I used 12 gauge and no problems with shading. I did this because I had about 18 large spools of wire that I got for free.