Thread: Panel volts exceeding MPPT controller

1. Re: Panel volts exceeding MPPT controller

Originally Posted by Photowhit
I wonder if run in parallel if the lower voltage VOC panel won't 'regulate' the higher voltage panel, similarly to how they work for peak VMP? Run in parrallel the CC only 'sees' the pair at the lower voltage.
No, because it's Voc; a panel being a big diode doesn't present any load to another panel. Put the two together in parallel and what you measure as Voc will be the higher amount.

2. Registered Guest
Join Date
Jul 2012
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Re: Panel volts exceeding MPPT controller

so I just checked the difference between the 2 panels...

panel 1:
VOC: 78 volts
VMAX: 61 volts

panel 2:
VOC: 61 volts
VMAX: 47 volts

definitely greater than 10% difference.... and then I think I was planning on stringing together a bunch of thin film metal cells... I have like 40 units of flexible 3.5v sheet that I would probably make into panel 3 which maybe could average between panel 1 and 2???

3. BB.
Just some guy
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Re: Panel volts exceeding MPPT controller

If it is "cheap"--Why not try it... You saw a 2x different in panels could result in a 25% reduction in output (again, don't know which peak the controller will pick).

-Bill

4. Fizzycist
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Re: Panel volts exceeding MPPT controller

Originally Posted by BB.
If it is "cheap"--Why not try it... You saw a 2x different in panels could result in a 25% reduction in output (again, don't know which peak the controller will pick).

-Bill
There is a very good chance that the controller will pick the wrong one. Since Vmp of one panel is close to and possibly higher than Voc of the other, as the CC starts to draw more and more current seeking the MPP, it will first find the MPP of the single higher voltage panel and will have no idea that it will be able to double the current by pulling the voltage down lower.
If there is an overlap, with Vmp of the higher voltage panel below Voc of the second panel, ,the CC should see only one peak, somewhere above the Vmp of the second panel.

On the other hand, if the CC tries to sample the voltage current profile over a wider range before zeroing in, it still may find the true maximum even with the first situation.

5. Registered Guest
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Re: Panel volts exceeding MPPT controller

I never spend money on anything... no tv, cellphone, I do my own haircuts, I don't buy pretty much anything but tools. so I have the funds to throw away on something like this, but as is everything else, it's always hard to justify haha

6. Re: Panel volts exceeding MPPT controller

I just reread this thread. Cariboocoot nailed it in the first response (post #2). For less than you spend trying to make your panels work, you could buy a properly matched panel and controller and generate more power. --vtMaps

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