question

As already advised, the capacitor has nothing to do with this behaviour.

The inverter should not shut down without a cerbo, it is not required to make the system work.

Have you manually set the correct settings on the inverter? When the cerbo goes, the mppts and inverter revert to their internal settings.

That it cannot work without a cerbo is indicative of a misconfigured system.

Your cerbo may well have a fault, or a bad cable/connection. Check that or have it replaced, nonetheless, the multi shouldn’t care and should just go into pass through.

The cerbo is reporting errors from two other components there, one is the battery, the second is the multiplus. Both are battery related issues. It is possible your ess settings are triggering the low battery on the Multiplus (although not likely if you have been running a year now) and your battery master is glitching in its comms with the cerbo. Or somethingnon the pack is a little unhappy (not uncommon with Pylontec).

Try switching your bank around (with a different address system) a bit and see if it uncovers an issue, or resolves the comms glitch.

The next thing to check would be all battery connections and dc cabling maybe something has worked loose or corroded or something like that.

The capacitor was for a select range of cerbos, and they prevented power pack faliure. If that was the issue, you would have no power on your cerbo.

I tried shutting down the batteries, with the system running. Cerbo didn't turn off as expected, its still powered by the car battery.

Mppt just disconnected, I guess as there is no sun it doesn't care

Mti logged the same low battery error, but this time with a voltage value, so I guess something different is happening here. Its not the batteries shuting everything off and then going back on.

Cerbo settings

A couple of things to consider.

A low voltage alarm is expected if the BMS is "lost", the question is why?

It can be a bad battery/bms, so try changing which battery is master.

Replace the cable used for the BMS-2-CERBO comms.

Please attach a copy of the multis config file here so we can check the settings.

Also, pull charts from VRM which show the battery voltage and current reported from the BMS and the same chart from the VE bus (multi), perhaps there is some loss along the way.