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Atomix avatar image

PV rapidly fluctuates between 1 and 130w in Bulk - Battery voltage spikes to 14.65 then drops.

Hi, I'm getting some worrying behavior from my set up today. Not something I've seen before. It's a mixed day with clouds and then full sun.

When overcast everything seems normal.

When the sun comes out the PV wattage jumps right up and the battery voltage spikes to about 14.65 volts. Then the wattage then immediately cuts right back to 1 and the battery voltage reduces to 13.3ish. The watts and voltage then jump up and rapidly max out again, and the cycle repeats.

It is doing this in both absorption and bulk mode. The absorption voltage is set to 14.4v and float is set to 13.67v.

My equipment is:

  • 100/20 MTTP
  • MTTP Control
  • 200w 24v Victron Panel
  • 100Ah 12v pure lead/carbon battery
  • BMV 700

Having done this all morning - rapidly fluctuate between 1w to 130w PV and 13.3v to 14.65v battery in both absorption and bulk modes - it's now stable in float at 35w and 13.64v.

Is this normal?

voltageerrorabsorption
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2 Answers
Atomix avatar image

Ok I've looked over my system and think I found the culprit... excessive flex in the solar panel. The panel wasn't laying perfectly flat and had a slight bend in it. I've since relayed it flat and the symptoms seem to have gone.

The suns nearly down for the day now, so i'll test again asap and close this thread when certain. Hopefully i've identified the problem and hopefully not caused any permanent damage to the equipment :o

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JohnC avatar image

Hi A. No, it's not normal. Enter troubleshoot mode..

You have both a BMV and MpptControl. Disconnect them both, by wire or BT links (make sure) to eliminate any outside influence. If the mppt still does it on it's own then it's likely faulty.

If it settles, then maybe something with the external kit?

But try that and come back..

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I've removed the BMV and MC (thought the BMV shunt is still in place) and the same thing is happening.

Looking at the "trends" graph it's really weird. When the sun comes out the PV current increases but the PV voltage drops dramatically, then the current drops and the voltage recovers. It looks as though when the current gets too high the system falters (too high being about 2 amps).

Is it possibly the PV panel or PV wiring, as that is the only part of my setup that changes/gets disturbed (I put the panel out on sunny days and store it inside when not in use)?