LFP, LiFePo4 batteries, cells bms etc.

[Dutch 68]

With that comment more likely to be to do with
The charger inverter. Most Victron inverter have a jumper inside allowing selection of loating earth or earth bonded to neutral,. Sound like he has it floating.

You are talking Chinese , can you translate that in language for people who are better in eating chocolate then electrics please Lenny?

 

[Lenny HB]

You are talking Chinese , can you translate that in language for people who are better in eating chocolate then electrics please Lenny?

Apart from a couple of slight typos which I have corrected it can't get much simpler than the way I explained it.
You can have the earth floating or bonded, bonded means the earth is joined to the output neutral, floating its not connected to the neutral.

 

[Raul]

If it’s a inverter synchronised to grid, it would simulate the grid, the victron does that and disconnects the earth from neutral when on grid as it has that already. May be a center tap inverter with leakage to chassis (inv case) that brings such a voltage to the earth side.