This is guess because I had this happen once before and could not figure out why GFI tripped only when the charger DC leads were connected to the batteries.
These symptoms suggest AC is passing into the DC charging circuit and returning via ships ground through the water (as well as via safety green also if it is bonded to ships ground as it should be.)
Measure for AC voltage between charger DC + leads and ships ground.
By the way - do not tie AC safety green to AC neutral anywhere on the boat. That means no such connection is allowed inside the charger or inside the microwave either.
Charles
These symptoms suggest AC is passing into the DC charging circuit and returning via ships ground through the water (as well as via safety green also if it is bonded to ships ground as it should be.)
Measure for AC voltage between charger DC + leads and ships ground.
By the way - do not tie AC safety green to AC neutral anywhere on the boat. That means no such connection is allowed inside the charger or inside the microwave either.
Charles