Solar charge controller voltage fluctuating heavily

DIY
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1

Hi,

I have 100/30 charge controller, with two 150w solar panels wired in series. When in bulk charging mode, I am getting very little solar charge, with my voltages from my solar system fluctuating from 9ish volts up to 45v, back to 9 and then 45 again constantly. This is on a completely clear day with no clouds, shading etc. I actually get slightly higher watts on cloudy days but similar voltage experience (video below)

Some things to note;

  • with the installer, we switched out the charge controller but continued to get the same experience.
  • re-wired the solar panels and tested them, all fine. All connections across system seemed good.
  • Shore charged the battery to 100% (battery is victron 300ah lifepo4) to get it into absorption and float mode but once it went back into bulk mode, kept happening again.
  • when it was in absorption and float mode, voltage fluctuation stopped.

The most I am getting in full sun is around 15-20watts. Typically it will touch 40-50watts if a bit cloudy. It’s almost like something is stopping it from allowing too much charge, but the shore charger and dc-dc engine charger are working just fine.

Any help would be greatly appreciated.

2

Wondering if anyone has any ideas on this or has seen it before that could point me in the direction at least to understand why it’s not producing hardly any power.

3

Your time was 7:18, so I suppose at the beginning of the day…
I’ve also noticed that in low irradiance - meaning at the beginning or end of the solar day - the behavior of the MPPTs are a little strange.
They are wandering quite heavily. Probably the way they implemented their algorithm.
Take a look at one of my MPPTs (the second from the videoclip) here: Strange behavior (bug?) of one MPPT in a Multi RS
In my case the panel configurations among trackers are identical - size, orientation, etc, - and you can see that the stable one (first) had settled on a much lower value (50W) than the value the array can give at max (100W).