Two possible issues.
One Battery v/s converter size. That box should be able to kick out around 100 amps charging as I recall but if you have several pair of GC-2 Well it will remain in bulk for up to 1 hour per pair possibly longer at full output.
Second Many Xantrex have "Shore Power Share" feature if you have it fed with a 30 amp breaker you tell it it's eating off a 30 amp breaker and if you are drawing say 25 amps.. for "other stuff" (120 stuff) via the inverter it will "Throttle" the charger so it does not trip the 30 amp breaker. This won't affect 120 volt loads as the only thing it Throttles is the charger.