I have an offgrid Victron Multiplus 5Kw, fronis inverter 5Kw (in MG50 mode), MPPT RS 450/200, 30kwh 48v lithium battteries with pylontech BMS
The problem is that when the battery is fully charged and a big load (toaster) disconnects suddenly the voltage surges up to 60v momentarily throwing a battery overvoltage error on the cerbo.
I decreased the fequency values in ESS slightly, but it still uses the AC coupling before the DC coupling.
Should I just keep decreasing the fequency values in ESS until DC coupling takes priority or is there a better way to make big loads draw from the DC side when at 100% charge?
As far as setting up the fronius I used the following instructions, there wasnt much to do except update to latest firmware and switch it to MG50 mode.
1.3 Setting up the Fronius with Setup MG50/MG60
When not pre-ordered with a MicroGrid setup, follow these steps:
Make sure that the Fronius PV inverter is updated to at least the firmware version mentioned above. See Inverter list above.
After making the inverter operational according to the manual, select the language and after this the country specific setup.
Here choose MG50 or MG60 depending on the system frequency.
I’m curius why the DNO settings requirements would be listed in the AC-coupled PV with Fronius PV Inverters [Victron Energy] document as something that needs to be done for on-grid ESS design installation manual but not mentioned in off-grid insructions. I will give that a go - Thanks.
Yes Fronius is using wifi and is seen correctly in GX
I’m still getting the error messages that happens when the batteries are 100% and a high power device is instantly switched off like a toaster popping up.
In this instance all the power is coming directly from either the RS or the fronius and they cant respond to the sudden reduction of load quick enough and throws an error.
Did you get to the bottom of this? I am have similar issues with a very similar setup by the sound of it. My difference is I get the high voltage when the sun pops out from behind the clouds and suddenly all the solar springs to life again. The system just cant rain it in quick enough. I have elevated the lower Hz value in the assistant to 50.8 in an attempt to be closer to the throttle down frequency of the inverter but still not controlling quick enough. Looking at all your screen shot mine is set up the same on the Fronius and in the Cerbo I can see all the Fronius details. Its almost like I need a setting in the Fronius to ramp on the output from solar at say 500w every X seconds to slow down the Fronius output, this wouldn’t cause any issues on a normal day as the sun rises on a clear sky day very smoothly ramping up the Fronius. Wouldn’t matter if it ramped over 1 or 2 minutes but it would be giving the system time to adjust and correct.
Oh and to some what combat your issue I have a staged loading system using home assistant. So starting at 85% soc I do two things. I have the cerbo start limiting the charge current every 5% rise in Soc, I reduce the charge current 25amps, so all the solar get throttled back both the AC and the MPPT. at the same time when the Soc hits 90% I have HA turn on the smallest AC a 1kw(of power consumption) unit, then at 93% it turn on the next biggest AC (2kw), and at 95% it turns on the Main ducted AC (6kw) and drops out the second biggest AC2kw. Unless its winter time or over cast an we have low solar production, in which case the load staging is disabled, however the charge rate is still enabled. This has the effect of the MPII’s limiting the output from the Fronius earlier. As it starts raising the freq at 90% SOC dependent on the Solar production
