michael avatar image
michael asked

Flickering Lights in home @ low PV/Quattro levels

Hello everyone, and thank you for any all helps and responses in advance.

  • My home is off the grid.
  • Its an AC coupled system, with a SMA sunnyboy 5kw inverter
  • I am running a Victron Quattro 48/8000.
  • I have 48kwh lead acid battery bank.

When my PV is at very low levels - hard to define a clinical level, but approx sub 300watts - i.e. in the morning at sunrise and evening at sunset, the lights in my home flicker / strobe.

Already tried:

1) I have tried it with old tungsten bulbs and with new LED bulbs - same issue across both.

2) When I increase the load in the house significantly (Over 1.5kw approx e.g. by turning on a heater) the issue resolves itself.
My normal base load/usage in the house is approx 350-450 watts but as you can imagine that is rarely constant.
Obviously I cant be running heaters/using excess loads just to resolve the issues as I live off the grid with limited power reserves.

3) We had the same issue with the fronius 5kw inverter we had in before - we then swapped this out for the SMA sunnyboy - exact same issue / no difference.

4) I have run my lighting circuits through an online UPS sinewave inverter - cures the issue immediately.

Given what I have tried above, have to be left to believe it is the Quattro, generating a poor quality sinewave/poor elecricity supply at low levels...

Is there a know issue at low levels with the Quattros?
(Ive searched the forums before posting - I cannot see anything)

What else can you suggest I attempt to resolve this issue?

Many thanks


MultiPlus Quattro Inverter ChargerPhoenix Invertersolarled
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moonlightrider avatar image moonlightrider commented ·


On a completely unrelated setup, with just a Multiplus 12/800 as UPS, when the Multi is inverting if I connect my (gaming) computer (with high quality PS) all the lights (LED or not) will flicker. I relate this to how switched power supplies work, they can cause harmonics and other interferences by switching on/off at the input.

I'm not sure if it's an issue with voltage regulator on the inverter or not.

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3 Answers
wkirby avatar image
wkirby answered ·

This is my interpretation of what is happening:
Basically, in AC-Coupled mode, the Quattro needs to be either a charger or an inverter. If there is zero or not enough PV, then it will be inverting and "tricking" the Sunnyboy (or Fronius) into being satisfied that a grid exists (LOM detection).
When there is more PV than the loads can soak up, then the Quattro becomes a charger and takes up the rest of the PV power and also satisfies the Sunnyboy's LOM detection.

As you have stated, there is a certain point where you loads are approximately ~300W and you PV is also making ~300W, so now the Quattro is in an awkward predicament where is is not supposed to doing anything (0 Watts). But, there is a problem, it's can't just sit there and do nothing otherwise the Sunnyboy (or Fronius) LOM detection would kick in and disconnect. If the Quattro inverts, then the house Voltage goes up, if it charges, the house Voltage goes down. It "hunts" very quickly in an effort to keep the Sunnyboy inverting, hence the flickering. If the grid were available, the Sunnyboy can go full blast and its contribution makes very little difference to the Voltage of the grid.
Switching on a heater is forcing the Quattro to invert, so it is in a stable situation, the Sunnyboy is giving all it can and all is well in the house (apart from burning electricity unnecessarily). Likewise, when the Sunnyboy is making more than the house is using, the Quattro can go into charge mode and dump the excess PV power into the battery.

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michael avatar image michael commented ·

Thanks for your response, your analysis definitely sounds logical.

What are the potential solutions?

How do I stop the lights flickering!?

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michael avatar image
michael answered ·

Hello Guys, just following up as hadnt received any potential answers/solutions yet or thjngs to try. If anyone has anynexperience of this would be very grateful, thank you for any and all responses.


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Guy Stewart (Victron Community Manager) avatar image
Guy Stewart (Victron Community Manager) answered ·

This might not be the solution for you, but in off grid situations I use a Victron DC MPPT to charge the batteries and run the inverter full time.

Flickering, overshoot, frequency changes effecting clocks and others are niggling issues with AC solar inverters in offgrid. They work, but not as smoothly in all circumstances DC MPPTs in my experience.

There was a firmware fix for Fronius that eliminated flickering when used off grid. Have you been able to get any comment from SMA?

In this specific situation, a dump load might sort it for you. You could program one of the Quattro relays to a contactor that only closes at high battery voltage or high state of charge and have it go to a hot water element.

That won’t negatively impact your usable power when you need it, but gives unused power somewhere to go rather than on/off cycling.

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