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Multiplus 2 Drops the AC grid then the PV inverter when the PV tris to connect


M2 48/5000, Fronius Primo 4500w set to MG50 on AC out 1, Cerbo GX, 5kw Battery connected on Can bus. - Self consumption, ESS, No Grid feed from PV. (Note the full battery is 20kw, the PV is 6kw, at present I only have one battery and one PV string 3kw connected. As I can discharge this battery over night and recharge by 1pm the next day allowing me to commission and confirm behavior)


The M2 will sync to the grid sits on about 110w regardless of load (300- 2500w), when the PV is ready it starts to push watts to the M2, as soon as it does there is a lot of relay clicking and the M2 disconnects the grid. The PV then starts pushing watts to the battery / load as expected, approximately 1 minute later the PV disconnects and goes through its full warm up process again. During this time the M2 reconnects to the Grid, and we start the dance all over again.

If I leave the Grid off, the PV connects and the system works, it will charge the battery, then throttle back as the battery reachs SOC and only provide the load. Perfect....accept there is no AC Grid for backup.

I cant seem to get around this, I have changed the ESS settings in the Cerbo to allow grid feed from the PV but no change. I have changed the GRID limit from 50w to 0 and 100w but no change.

My temporary solution is to have a contractor in the grid line controlled by the cerbo generator function, if the SOC gets to 17% connect the grid and charge to 25%. This works but it happens during the night with no PV. it also takes about 1 minute for the grid and M2 to be happy and start taking from the grid, too long in a surge event or battery issue.

I am sure I don't have a setting correct in the cerbo or the ESS config, but I cant find it.


M2 with grid backup, AC coupled PV, battery in self consumption mode, running the house.

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