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groningen avatar image
groningen asked

MultiplusII switching from battery to grid is slow

Dear ALL


I have two 5kva MultiplusII running in parallel. I am running ESS with panels, mppt's, cerbo gx etc.

This system has been running fine for almost two years.


Lately, the system takes very long to switch back to the grid (when grid returns from outage).

The other setup (multiplusii) on premises returns quickly (the same as it was for the above system before).


I know other factors should be considered i.e. Grid code in ESS, voltage, frequency, etc, but I always run "wide frequency and set the voltage to limits". So this should not effect the slow changeover.

I did not change anything and as stated above, the "return" switchover is now very slow.

So I am somewhat dumbstruck that the system takes this long to return from grid.


What could it be? I restarted the system a few times hoping it will just be a reboot to fix all.


The only thing that I might have done a few months ago is to load the new Cerbo V3.32.

Could this be it?





Multiplus-IIcerbo gx
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6 Answers
nickdb avatar image
nickdb answered ·

Unlikely to be firmware related. Sounds like it is having an issue accepting grid, so you need to check that, or what else could be affecting grid quality on power return.

Have you tried doing a test grid loss yourself under clean conditions to check if it behaves the same?

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groningen avatar image
groningen answered ·

@nickdb


Yes, I did a "mains fail" (with stable supply and frequency) but to no success w.r.t. return to grid.


I noticed that as soon as I switch off the Inverter and switch it back on, the grid returns.

????

......but than, when I do a mains fail again, the system takes long - 30 min to 60 min to accept Grid.


Hardware issue?



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groningen avatar image
groningen answered ·

@nickdb

Also, I noticed that when I "take" off all loads from inverter (lets say from 3000W to 150W) it takes the grid.


When power comes back on, the ground relay kicks in, but just not the grid.


So I guess, the summery is, if load is present and grid returns, the inverter does not accept the grid ????

Any ideas would be appreciated.


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nickdb avatar image
nickdb answered ·

Testing can be annoying.

Try swap which unit is master.

If that doesn’t help, try switching to standardalone and test each individually.

If there is a difference it will become apparent.

There are also a fair number of stats you can pull directly from each inverter over mqtt which may help highlight what they are seeing individually.

What firmware are the inverters running?

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groningen avatar image
groningen answered ·

@nickdb


thanks for the tips.


It is running 502 on both.


Will try the to swap Master and check.


I have not "played" with MQTT before so I am slightly hesitant (just because of my own knowledge, unless you have a quick guide video on hand).



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groningen avatar image
groningen answered ·

Just an update


I disconnected all wires (to inspect) and checked software.

For now, all is stable, but I did get a "sync time out" which only happened once before removal. I am not sure if the sync is reference to the LAN cable running between the parallel units (VE Bus). Maybe a little bit interference?


Nevertheless, all is up and running, happy days.



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