# question

asked

## Hmm, why does pv voltage drops when connecting to solarcharger 75/10

I am quite new with all this solar electronics, so i hope the question aint that stupid, i have 2 small solar panels (2 x 18v; 16w) in series connected, measuring between the poles shows me a voltage of 36v, i connect the panels to the victron 75/ 10 mppt controller and gives me a reading of 12,35v on pv :/, I have a lithium-ion battery 12,6v 15ah connected, why does it show such low voltage i do not understand, who can shed light on the issue, thanks in advance

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2 Answers
petajoule answered ·

also, please make sure you understand the relation between current, voltage and power, because that is what your MPPT (Maximum Power Point Tracking) is doing.

It has nothing to do with Powerpoint from Microsoft, it's the tracking of the point of maximum power (output) of the PV panel at a given time.

Your question is actually just another wording for this question:

https://www.quora.com/What-is-the-difference-between-open-circuit-voltage-and-output-voltage-in-a-PV-panel

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I'll read them carefully thanks

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sinusmagus answered ·

As i was testing yesterday, clouds were shading the panels, altough 36v, there was low current, setting mppt at low voltage, today i raised to 54v, in direct sunlight, all confusion solved ... as the battery is charging, awesome :)

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Glad to hear the system is working now.

If that didn’t work, or for someone else in the future with the same question;

A symptom of a panel that is incorrectly connected to the MPPT in reverse polarity is that it’s voltage drops when connected. So if it’s not just clouds like what has fixed it in your case, try reversing the polarity of the PV array into the MPPT and that might also fix it. Or even better TEST the polarity and voltage of the solar array BEFORE it is connected to the MPPT.

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