question

Normally in an ESS system the multiplus wants to respect the charge Limit. It does so in an offgrid situation by increasing the output frequency which throttles down your PV Inverter IF everything is configured correctly on the Victron and Fronius side.

It is described in the Victron ESS manual how this frequency control works: https://www.victronenergy.com/live/ac_coupling:fronius

So yes in a functioning System the 5a limit will stay in place and Fronius will throttle down or puts out 0w.

I did not really understand though why mppt rs ignores the CCL

"I did not really understand though why mppt rs ignores the CCL"

It does ignore CCL, if you enable DC-feed-in. Thats required by design, otherwise you won´t have excess current available to feed into grid.

there are several threads about this behaviour in the forum.

But thats fine. That works great for me. Battery charging is limited then by CVL only.

"So yes in a functioning System the 5a limit will stay in place and Fronius will throttle down or puts out 0w."

Yes, that will work over time. But at a sudden loss of grid during full PV-Power (like described at Factor 1.0 rule instructions), the PV-Power must be redirected immediately. As throttling the PV-inverter takes some time.

but the power must go somewhere. This is only an issue for a few seconds.

Usually Power is redirected into the battery then, until throttling is complete.

If allowed, every 5kVA multi should be able to charge 70A into the battery in this case.

But at the same time, i would have a 5A limit active that should prevent this "power relieve"

Therefore my question is:

is this CCL ignored for those few seconds of this PV-Power relieve?

Can the multis even sustain this limit, or do they have no other chance then just letting the power go through in this case?

I mean it must either go somewhere or some device must shut off, isn´t it?

okay now I think I fully understand your concern. And I am familiar with these important few seconds actually. There could also be a Problem like this when you reconnect to the grid.

Say your battery is at 100%, CCL is at 0 amp and Frequency is at 53 hertz (i believe its 53 for fully throttled down fronius).

When Grid comes back the multiplus will try to match the grid frequency again which throttles up your Fronius to 100% with the grid not yet connected.

That Situation will eventually trigger some emergency shutdown because voltage will rise but still has a good chance to damage the multiplus or your batteries. The Multis will let power through since they are "only" a variable voltage source and the PV Inverter will cause the voltage to rise very fast above the multi's voltage when the power has nowhere to go. So current will flow through the multis in the battery.

I solved this problem once with a different solar inverter. I programmed the auxiliary relais in the Multiplus to turn off the Solar Inverter immediately for 3 minutes when we loose grid and when grid is available again.

That gives the Multiplus time to connect to the grid and on the other hand gives time for frequency shift to start after gridloss.

There may be a better solution for Fronius though. I am not very familiar with fronius, in the case I described an old "dumb" SMA was used which didn't even have internal monitoring.

sorry for late relpy.

"I programmed the auxiliary relais in the Multiplus to turn off the Solar Inverter immediately for 3 minutes when we loose grid and when grid is available again"

That sounds like a good idea. I think about doing the same.

Is this possible by Victron settings only? Or did you install an external 3min timer relay?

Also i will change CCL to max. Battery suitable value once off grid. (via modbus).

Because during off-grid situation my limit makes no sense anymore.

i think this should cover all those situations quite well then.