There was already a problem in the parallel configuration of the 2 Multiplus Compacts. One of the Multiplusses made a terrible noise. CMP242020000 HQ1341JBATN
After disabling the parallel configuration, I did a firmware upgrade to FW2618494.
Configured with VEConfig3 and MK3USB with the same settings as the other (working) Multiplus.
When switched ON this Multiplus still makes a terrible noise with only the battery bank (12V) connected. No loads, no grid.
suspect one of the units power packs has been damaged - never turn 2 single phase units on at the same time or you will damage them due to a output short - correct installation and configuration is important - suggest you configure both for stand alone operation the run ONE inverter and see if it works well then turn that one off and rn the other if bot work fine in standalone then reconfigure for parallel operation as per the victron instructions. if one inverter does not work then this will need repairing.
or you could even have incorrect wiring as well
