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I have two banks of 6 x 270W panels on my roof (3 in series, paralleled): 
And I have a Victron 150/35 on each bank (West and East): 
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: 
(Around noon, there was a grid failure around 12:10 today - why did yield fall to 0 when that happened?)
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.
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).
Hi, have any one resolved this issue with victron?
We have a 5kw multiplus II with the same issues
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.
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.
i got 3 of those charge controllers and mine does that when the battery is nearing full capacity. It dials back the solar production.
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)
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.
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
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.
All available at https://vrm.victronenergy.com/installation/34733/advanced
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: 
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.
You should be able to see the Multi's graphs in the widgets section under VE.Bus. That should show you what's happening.
@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)
Hi Warwick, what are you asking? yes the Multi can derate due to temperature.
That has nothing to do with your MPPT of Venus
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.
