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surfamj avatar image
surfamj asked

Adding second solar array in parallel doesn’t double output but stays same

I added a duplicate array of 4 x 200 watt panels in parallel to my Victron 100/30 controller. My first array is wired in series and would produce about 420 watts on a sunny day. I figured I would add another 4 identical panels in series as a second array and then wire the two arrays in parallel. I assumed I would double my output but it stays the same. I can disconnect either array and get the same result. Am I doing something wrong or is this normal? I know the voltage and amperage are under the 100 volts and 30 amps of the controller.

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wkirby answered ·

You did not say what your battery Voltage is, I'll presume that it is 12V.

Your charge controller is a 100/30. That means that your PV array must not exceed 100V. I think you have understood that part already.
The 30 means that the maximum output charging current to the battery is 30A. The charge controller limits this it's self.

So, your battery Voltage increases as it charges it will go to around 14.2 - 14.8V depending upon your battery chemistry. Let's take 14V to make the maths easier.
To get the charge power you multiply the battery Voltage by the current. 14V x 30A = 420W.
This is the 420W that you have observed, adding more PV will not result in any more production. In fact your first array is a 800W array, so it was only partially utilised on a sunny day.
If you have added another 800W, then you'll only really benefit on cloudy days where you could still see the 420W in cloudy weather.

So the bottom line is that your charge controller is undersized for your first array.
You would need a 150/60 just for the first800W array on its own. 14V x 60A = 840W
Then you'd need another 150/60 charge controller for the second identical array.

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surfamj avatar image surfamj commented ·

Ahhh, thanks for that explanation. It really helps a lot! If all the panels are identical then does it make any sense to have a larger controller that can handle both arrays? Or is it more efficient to have 1 controller for each array?

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michelg answered ·

What is the voltage of your battery bank, or batterie ? also, an hello, please and thanks are welcome !

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surfamj answered ·

I have 4 x 12.8 volt LiFePO4 batteries.

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