Which is better, Series or Parallel panels

The input voltage limit for a controller is the array total panel Voc (NOT Vmp), which must be corrected for actual conditions where the panel Voc might be higher than its rating, such as in cold temps.

When doing calculations for amperage using a PWM controller, you use the panel's Isc as its expected max amps when pointed at a high sun.

Vmp and Imp have absolutely no meaning with PWM!!! Those are strictly for MPPT calculations (Vmp x Imp = input watts to the MPPT controller when it is in "MPPT mode" which is "Bulk" in MPPT language)

CA Traveler wrote:

brulaz wrote:
With series 24V (nominal) panels you might exceed the max input V of the controller? My controller's max input is 100V, Vmp of many (72 cell) 24V panels is ~36V.

May not be a big deal with just 3 panels. But with 4 24V 72 cell panels, I wouldn't do it.

Voc is the critical voltage and should not exceed the controllers maximum input.

My Voc is 112V. 4 panels would be 150V and not good for my MPPT60 150V controller limit for example.

Ah right, that makes sense. My panels have a Voc of ~44V, so 3 would exceed the controller's 100V max.

brulaz wrote:
With series 24V (nominal) panels you might exceed the max input V of the controller? My controller's max input is 100V, Vmp of many (72 cell) 24V panels is ~36V.

May not be a big deal with just 3 panels. But with 4 24V 72 cell panels, I wouldn't do it.

Voc is the critical voltage and should not exceed the controllers maximum input.

My Voc is 112V. 4 panels would be 150V and not good for my MPPT60 150V controller limit for example.

pigman1 wrote:
I asked the same question of an engineer at Northern Arizona Wind and Sun as specifically applied to my 6 Kyocera 140W panels and Morningstar MPPT controller. He said that the parallel wiring was the most efficient in so far as partial shading of a portion of one or more panels or totally shading one or more panels for my installation. The down side is higher line losses and higher costs for heavier cabling.

This is correct: panels in series, current is limited to the panel in the most shade.

The math from what I've seen.
Two panels in series, Vmp = 18.1 volts, Imp = 4.47 amps.
Watts for full sun (Vmp1(18.1) + Vmp2(18.1))* 4.47 amps = 162 watts
Partial shading of one panel reduce totals watts by 60 to 80%
162 watts * 0.2( 80% reduction) = 32 watts

Watts in parallel full sun Vmp1(18.1)*4.47 amps plus Vmp2(18.1) * 4.47 amps or the same 162 watts
for parallel one in shade: Shaded panel Vmp(18.1) * 4.47 amps * 0.2(80% reduction) = 16 watts + 81 watts(non shaded watts) = 97 watts

Thanke for all the posts info.
I'll leave it in its parallel configuration.

I hate my new "Solar 30" controller, so thought when I make a change I mite go series, but I'll leave as is,.....it works fine.

With series 24V (nominal) panels you might exceed the max input V of the controller? My controller's max input is 100V, Vmp of many (72 cell) 24V panels is ~36V.

May not be a big deal with just 3 panels. But with 4 24V 72 cell panels, I wouldn't do it.

Looks like 12v panels so parallel is likely better.
At the same time I am not sure the difference would be huge.
Still might get 50% out of series and have the battery charged by 3pm instead of noon.

Parallel may very well be the best option for 12V panels. It's also dependent upon the configuration of bypass diodes and other factors.

In my post above the panels are 24V panels and 2/3 of 1 panel can still charge the batteries as the graph shows. This seems to be rather common for 24V panels.

I did not read this before I posted


"I asked the same question of an engineer at Northern Arizona Wind and Sun as specifically applied to my 6 Kyocera 140W panels and Morningstar MPPT controller. He said that the parallel wiring was the most efficient in so far as partial shading of a portion of one or more panels or totally shading one or more panels for my installation. The down side is higher line losses and higher costs for heavier cabling."

I have no idea what I am doing so I am going to ask the question. In my situation I have 4 140 watt Kyocera panels and I find that with running them in parralel that I will always get some charging no matter if one panel is shadded. I would think this is the better way to go other then the expense and voltage drop of the heavier guage cable.