question

Elimac avatar image
Elimac asked

Strange PV voltage spikes during night

I have bought recently a new MPPT, this time a 150/70. It is fed with 2 strings in parallel of 3x REC 275W pannels in series. They were previously assembled as a single 6x 275W in series string connected to another 250/60 with no issues.


I noticed some strange 7V peaks appearing radomly during the night on PV side:


Another example, zoomed in:


I find this odd and never saw the same in other MPPTs, even with same panels. What could be the cause? Any ideas?

This MPPT 150/ 70 is running latest FW 1.47.

MPPT Controllers
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Alexandra avatar image
Alexandra answered ·

Solar panels pick up all light even full moon i have seen our mppts at 13V. It is not enough to charge anything as there is no Amps. The spikes may be the moon moving out from behind cloud. The other possibility is a security light behind some trees moving in the wind. When the security guard is doing his patrol and shining his torch over the panels we also get some voltage readings.


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Elimac avatar image Elimac commented ·

Thanks for the input, but I don't think any of the above can be the cause:

1) There is no moon in consecutive 30 days.

2) I don't live anywhere near where there are such thinhgs as security guards with torches ;)

3) There's no artificial light near by and or with trees and it would be strange how the peaks are so close to 7V everytime. If out conditions were to blame, I would expect random voltages to be reached, and not even necessarily as spikes...

4) Lastly, and more important than the above, the same pannels, same location, same installation - only broke 1 string in two - produced clean graphics with a 250/ 60 MPPT.

Only extra hardware are 2 fuses and a box. And the new 150/70 mppt, of course.

But, your post made me think of a possibilty.... to test it, I will disconnect the PV side next week on some nights.

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Alexandra avatar image Alexandra ♦ Elimac commented ·

Disconnecting the PV sounds like a good test. I would be interested to know how that goes.

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Alexandra avatar image Alexandra ♦ Alexandra ♦ commented ·

Hi @Elimac How did your test go? We are keen to hear if there was a behavior difference!

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Elimac avatar image Elimac Alexandra ♦ commented ·

In the nights I disconnected PV (about 2 or 3) the spikes did not happen. I'm happy with this, as my main concern is the mppt state. So, assuming it was not a coincidence, the issue comes from the outside.


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