Is there a way to limit Maximum PV voltage to controller?

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maxxmanic asked Jun 7, '20

Is there a way to limit Maximum PV voltage to controller?

I have a 100/20 Smart Solar controller and only 2ea 100w panels. I want it to operate at full capacity by adding panels. Due to conditions on my property I need a longish cable run from my panels to the controller. High current and long runs seem to be expensive due to the cable thickness required. I want to add enough panels, in series, to get close to 100v but am worried about damage to controller. How can I “over voltage” the panels and reduce that voltage at the controller. For example, I envision a voltage limiter of some type. Say feed 150v from panels in and get 100v max out to put into controller. Is such a thing possible? Also, why is the PV input voltage so low for the controllers? Sorry for my ignorance, and thanks for the explanation.

Maxx

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Answer 1 · 2020-06-07T15:27:34Z

wkirby answered · Jun 07, 2020 at 03:27 PM

Ideally, you'd not want to limit the Voltage as this would waste PV energy. The energy that you don't want going to the MPPT controller would have to be wasted as heat.
A DC-DC converter would solve this problem to an extent, but you still loose energy in the conversion.

Unfortunately, the only real way is to use an appropriate charge controller, one with higher PV input Voltage.

With regards to low PV input Voltage, there are a few reasons:
Lower Voltage transistors used withing the converter of the MPPT are cheaper than higher Voltage ones. This is reflected in the range of MPPT controllers available, the smaller ones are cheaper than the bigger ones.
MPPT controllers used in DC coupled systems have a lower Voltage input than those in AC coupled systems due to the output Voltage being low. Battery Voltages are lower than AC mains Voltages.
There is more energy loss in converting a higher Voltage into a lower Voltage. Put another way, the closer the input Voltage is to the output Voltage, the more efficient the conversion will be.

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