question

Warwick Bruce Chapman avatar image
Warwick Bruce Chapman asked

PV Sudden Dropoff

I have two banks of 6 x 270W panels on my roof (3 in series, paralleled): alt text

And I have a Victron 150/35 on each bank (West and East): alt text

Can anyone explain the sudden drop-off on the West MPPT. I took the photo above at the time screenshot from VRM to show you there was no shading.

My composite yield graph for the day looks like: alt text

(Around noon, there was a grid failure around 12:10 today - why did yield fall to 0 when that happened?)

MPPT ControllersSolar Panel
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yield.png (127.8 KiB)
3 comments
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ejrossouw avatar image ejrossouw commented ·

Hi @Warwick. Do you feed excess into the grid? Could it be that demand dropped away and output reduced and as others suggest, the charger throttles back because battery is also full? My mppt throttles back once battery is full as there is no other demand other than a fridge and alarm.

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Warwick Bruce Chapman avatar image Warwick Bruce Chapman ejrossouw commented ·

Yes I do. There was a grid failure at 12:10 today but at 09:31 all was well from what I can see (refer to screenshots in my reply to Daniel below and in my possible answer).

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entero-energy-wc avatar image entero-energy-wc commented ·

Hi, have any one resolved this issue with victron?

We have a 5kw multiplus II with the same issues


1669219690629.png

This is the PV yield for 8 days with clear sky's, we are allowed to export all access power to grid if grid is available.

1669219870599.png

On the system we have 10Kwh batteries installed to help the system during cut grid loss and during the night.

We have been battling close to a year to try to sort this out with no successes.

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3 Answers
dustdevyl avatar image
dustdevyl answered ·

i got 3 of those charge controllers and mine does that when the battery is nearing full capacity. It dials back the solar production.


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Warwick Bruce Chapman avatar image Warwick Bruce Chapman commented ·

But we have feed-in enabled so whatever the batteries and house loads can't take, the grid should receive. cc @Daniël Boekel (Victron Energy Staff)

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ejrossouw avatar image ejrossouw Warwick Bruce Chapman commented ·

I stand to be corrected, but there should not be feed-in to the grid when there is a power failure, so production will be cut back if the batteries are full. That is my thinking. Download the raw data and that could shed a light on what happened at the grid end.

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Warwick Bruce Chapman avatar image Warwick Bruce Chapman ejrossouw commented ·

Correct but no grid failure at that time. You can see at 12:10 what grid failure looks like - it went away for 1 minute. @ejrossouw

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Daniël Boekel (Victron Energy Staff) avatar image
Daniël Boekel (Victron Energy Staff) answered ·

Hi @warwick

Please show the battery voltage / current graph, that probably shows what @dustdevyl is expaining.

The battery reaches absorbtion voltage, and one controllers backs off when the other can provide enough current to maintain absorbtion voltage. A second step can happen when switching to float.

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Warwick Bruce Chapman avatar image Warwick Bruce Chapman commented ·

All available at https://vrm.victronenergy.com/installation/34733/advanced

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Warwick Bruce Chapman avatar image Warwick Bruce Chapman commented ·

alt text

Nothing jumps out at me.

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Warwick Bruce Chapman avatar image
Warwick Bruce Chapman answered ·

Here's a theory @Daniël Boekel (Victron Energy Staff).

The system has a MultiPlus II 3000VA which is about 2200-2400W depending on the temperature (and it is very hot and sticky here right now).

Note that at the moment before the drop, the PV was producing just under 2400W: alt text

What are the chances that the MultiPlus derated because it got too hot from trying to push 2400W to loads and the grid.

I don't seem to be able to find a graph in VRM that shows the total AC power produced by the MultiPlus including that which was exported to the grid.


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JohnC avatar image JohnC ♦ commented ·

You should be able to see the Multi's graphs in the widgets section under VE.Bus. That should show you what's happening.

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Warwick Bruce Chapman avatar image Warwick Bruce Chapman JohnC ♦ commented ·

@JohnC I don't see this in the AC graph but I'm pretty sure this is happening either since MPPT 1.47 or Venus OS 2.42 despite neither changelogs mentioning anything about it.

cc @Daniël Boekel (Victron Energy Staff)

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ejrossouw avatar image ejrossouw Warwick Bruce Chapman commented ·

Have you tried replicating this yet or a fluke one off maybe?

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Warwick Bruce Chapman avatar image Warwick Bruce Chapman ejrossouw commented ·

Yes it is happening every clear sunny day now.

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Daniël Boekel (Victron Energy Staff) avatar image Daniël Boekel (Victron Energy Staff) ♦♦ Warwick Bruce Chapman commented ·

Hi Warwick, what are you asking? yes the Multi can derate due to temperature.

That has nothing to do with your MPPT of Venus

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Warwick Bruce Chapman avatar image Warwick Bruce Chapman Daniël Boekel (Victron Energy Staff) ♦♦ commented ·

It is not derating because of temperature but power. The solar array can provide more power than the multi can invert - hence the overload warning I had been getting for some time now.

I can not pinpoint the change but it seems around 1.47 MPPT it Venus 2.42, the overload warnings stopped and instead one of the MPPTs started derating output.

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