For most batteries if you have enough converter you can fully charge them from 50 percent in around 5-6 hours, LIFELINE AGMs you can cut about an hour off of that if you have a big enough charger, Darn few do.
Most batteries the recommended max charge rate is 30% c/20 that is if you have say a 100 amp hour at the 20 hour rate battery, 30% of 100 or 30 amps.
LIFELINE AGM is the only one I have seen recommending more than that, like 10 times that, so you can hit that same 100 amp hour box with 300 amps.
Biggest converters I have seen for RV use are in the 100-120 amp range.
So, you have say six GC-2 batteries (690 amp hours) how fast can you charge them?
I can (in theory) hit 180 amps (multiple converters) but.. In practice perhaps 110 Beyond that Id need a bigger converter.