Hi,
I have a Victron Multiplus 500va. It's been working fine. I then bought the VE.Bus Smart Dongle and at the weekend connected it all up.
With the VE.Bus Smart Dongle disconnected, the Multiplus charges the battery fine when on mains supply. When I link in the Smart Dongle, the fault light comes on on the Multiplus and the app for the Smart Dongle shows the error 'Low battery' and it switches to AC passthru rather than charging.
The Smart Dongle is powered directly from the battery + and its negative supply is from the output of a Victron bluetooth shunt.
Any clues as to why Low battery is being reported?