Wiring solar panels in series with three panels

[Vintage465]

So I am now messing with the idea of configuring my solar into a series set up. I currently have 2 each 150w Samlex panels. I am going to put a third matching panel up there.......that is all the realestate there is on the roof. So I've heard from a pretty "well read" friend of mine that I can wire two of the panels in series and the third one can just be wired in parallel................long as you use an MPPT controller. Thoughts on that idea?

Thanks

[pianotuna]

volts in series rise; amps in series do not rise

Amps in parallel rise; volts in parallel do not rise.

And watts stay the same.

Output from the panels wired in series in theory will be:


55.14 volts and 8.82 amps.

In real life, you may see 55.14 volts and 6 or 7 amps at solar noon.

In the morning you may see 55.14 volts and 1 or 2 amps.

Vintage465 wrote:

So I totally get the wiring now! This looks easy. Now lets talk amps. Each panel is 18.38v/8.82 amps. Do the amps triple like the voltage? Adding up to a theoretical high of 26.46 amps? Or do the amps stay an 8.82?

Thanks,

[time2roll]

Parallel: add amps, not voltage.

Series: add voltage, not amps.

[BFL13]

The panel specs don't come out right. 18.38 x 8.82 = 162, but in the OP it said they are 150w. For their watts , use the Vmp and Imp figures.

For the amps you can get using PWM use the Isc figure. For the voltage wrt to the controller's input limit, use the Voc.

When using an MPPT controller (a buck converter) your array amps will be one thing and amps to the battery another depending on the input and output voltages.

[red31]

160w = 18.38v * 8.82A
320w = 18.38v * 17.64A parallel or 36.76v * 8.82A series
480w = 18.38v * 26.46A parallel or 55.14v * 8.82A series

[DrewE]

Vintage465 wrote:

So I totally get the wiring now! This looks easy. Now lets talk amps. Each panel is 18.38v/8.82 amps. Do the amps triple like the voltage? Adding up to a theoretical high of 26.46 amps? Or do the amps stay an 8.82?

I think an analogy here might help. Think of your solar panels as electron pumps, sort of like water pumps. The voltage is the pressure the pump produces, and the current (amperage) the flow of electrons.

If you connect your pumps together in parallel, the pressure (voltage) is the same, but you get three times the flow rate (amperage). If you hook them up in series, one after the other, the same stuff flows through each of them so the flow rate (amperage) is the same but the pressure (voltage) is tripled.

[Vintage465]

2oldman wrote:

Vintage465 wrote:
So, how would I wire a third panel in series?

Sorta like the other two.

So I totally get the wiring now! This looks easy. Now lets talk amps. Each panel is 18.38v/8.82 amps. Do the amps triple like the voltage? Adding up to a theoretical high of 26.46 amps? Or do the amps stay an 8.82?

Thanks,

[2oldman]

Vintage465 wrote:
I will draw a little schematic of what I think you mean here and post it tomorrow and then we can see if I really do get it.

Sure, you can use the schematic I posted above as a guide.

[Vintage465]

MrWizard wrote:
It's a series daisy change +- +- +-
The positive from one end and the NEG from the other and are the input to the controller

Similar to wiring 6v batteries only it's three solar panels

I think I might understand this. I will draw a little schematic of what I think you mean here and post it tomorrow and then we can see if I really do get it.

Thanks

[Lwiddis]

He’s NOT well read regarding solar.

[BFL13]

Vintage465 wrote:
Thanks for all the great info. It didn't sound right trying to run two in series and one stacked on top in parallel. I suppose it would be similar to have two six volts batteries in series, then paralleled to 1 group 27, 12v. Though I think there is a better possibility of that working (though not well) than trying that with solar.

No, two 6s in series in parallel with a 12 is ok, as mentioned above in the thread.

[2oldman]

Vintage465 wrote:
I suppose it would be similar to have two six volts batteries in series, then paralleled to 1 group 27, 12v..

No, actually that's possible because the voltages are equal.

Your friend advised you to hook 3 6v batteries in series with one 12 panel in parallel.. so to speak.

[Vintage465]

Thanks for all the great info. It didn't sound right trying to run two in series and one stacked on top in parallel. I suppose it would be similar to have two six volts batteries in series, then paralleled to 1 group 27, 12v. Though I think there is a better possibility of that working (though not well) than trying that with solar.

[BFL13]

Vintage465 wrote:
So, how would I wire a third panel in series? I can't visualize that.

Thanks,

Outside end panels and middle panel. Take the pos from one end and the neg from the other end to the controller. Join the neg to the pos among panels

[MrWizard]

It's a series daisy change +- +- +-
The positive from one end and the NEG from the other and are the input to the controller

Similar to wiring 6v batteries only it's three solar panels

[2oldman]

Vintage465 wrote:
So, how would I wire a third panel in series?

Sorta like the other two.