question

That's strange. The MultiPlus can only really output the same Voltage no matter how heavy load is (within its design limits of course). This leads me to believe that something is up with the house wiring.

If you apply a Multimeter right at the output of the MultiPlus does the Voltage remain constant or does it vary with different loads. If the Voltage reamibs constant like it should then you need to look towards poor house wiring.

Check your DC section...

- What cables cross-section are you using

- What DC fuse are you using between batteries and Inverter

- Measure the DC voltage when large loads are running

- Measure the DC voltage when light loads are running

- Check in the logs the current spikes/ peak power needed to turn on some loads (fridge, etc)

- Is there any other element besides a fuse between batteries and Inverter?

What is your battery bank configuration? 24x 400Ah in series? Can you tell the battery module spec? Internal resistance should be checked on paper at least.

I suspect (just a hunch) too much resistance on DC side.

Someone should hopefully be going to site in the next week to check the voltage measurements.

The battery bank is 4 strings of SacredSun 100Ah PbC batteries with an internal resistance of 5mΩ when full. I believe the fuses are 160A(?), two banks per small HRC going into one large HRC for a single point of isolation. Cable cross-section of 35mm² on each string, 50mm² for the final cables going into Multiplus.

Hi @Sparkynz, thanks for your enquiry. We had a similar situation with one of our installers clients recently on a DC coupled system, that was grid tied too (in Zimbabwe). When grid failed, and the system was inverting, the lights would flicker. When I went to check and did some tests, I found there were issues with the earth bonding between the Victron system and the house, as well as with the house and earth/neutral bond at source. This was rectified accordingly and the homeowners apparently do not experience this any longer? I too, as with @WKirby, feel this is more likely related to the house electrical reticulation rather than the Victron system? Assuming the tests suggested by @Elimac have passed with flying colours.

Keep us posted? Hope this helps...

Thanks, dagga, we hadn't seen it on any of our previous installs so good to know it's not an isolated occurrence. I've added your comment to the service notes and I'll let you all know how it goes.

I had exactly the same issue, the lights (led and flouro) flickering as loads change. this was in a stand alone system with the lights directly wired to the breaker outlet.

The Problem was the power to the inverter, it was the batteries, Cables were 2x95mm with a 5m return run to a 24v 3kw inverter, with only one main fuse and isolator.

What is the Victron recommendation in the manual for cable size, length and breaker size for your multiplus?

Darren